From 3583a4bb33a8af40c425f0257e41fd3f46791ba3 Mon Sep 17 00:00:00 2001
From: xiaoma20082008 <chunxiao_ma@outlook.com>
Date: Tue, 23 Nov 2021 15:44:00 +0800
Subject: [PATCH] <feat>: refactor the velocity-engine to be more scalable

---
 pom.xml                                       |   1 +
 velocity-engine-core/README.md                |  62 ++
 velocity-engine-core/pom.xml                  |   6 +
 .../java/org/apache/velocity/api/Node.java    |   8 +
 .../org/apache/velocity/api/Resource.java     |  99 ++++
 .../org/apache/velocity/api/Template.java     |  13 +
 .../apache/velocity/app/VelocityEngine.java   |  19 +-
 .../java/org/apache/velocity/spi/Cache.java   |  25 +
 .../org/apache/velocity/spi/Compiler.java     |  28 +
 .../org/apache/velocity/spi/Converter.java    |  25 +
 .../java/org/apache/velocity/spi/Loader.java  |  31 +
 .../java/org/apache/velocity/spi/Parser.java  |  29 +
 .../org/apache/velocity/spi/Translator.java   |  29 +
 .../apache/velocity/spi/caches/MapCache.java  | 116 ++++
 .../velocity/spi/compilers/BaseCompiler.java  | 111 ++++
 .../velocity/spi/compilers/JavacCompiler.java | 306 ++++++++++
 .../spi/compilers/JavassistCompiler.java      |  30 +
 .../spi/converters/MultiConverter.java        |  42 ++
 .../velocity/spi/converters/XssConverter.java |  68 +++
 .../velocity/spi/loaders/BaseLoader.java      | 153 +++++
 .../velocity/spi/loaders/ClasspathLoader.java |  39 ++
 .../spi/loaders/DataSourceLoader.java         |  39 ++
 .../velocity/spi/loaders/FileLoader.java      |  40 ++
 .../velocity/spi/loaders/JarLoader.java       |  40 ++
 .../velocity/spi/loaders/MultiLoader.java     |  66 +++
 .../velocity/spi/loaders/UrlLoader.java       |  37 ++
 .../velocity/spi/loaders/ZipLoader.java       |  37 ++
 .../spi/loaders/resources/BaseResource.java   |  84 +++
 .../loaders/resources/ClasspathResource.java  |  40 ++
 .../loaders/resources/DataSourceResource.java |  46 ++
 .../spi/loaders/resources/FileResource.java   |  41 ++
 .../resources/InputStreamResource.java        |  82 +++
 .../spi/loaders/resources/JarResource.java    |  42 ++
 .../spi/loaders/resources/StringResource.java |  57 ++
 .../spi/loaders/resources/UrlResource.java    |  42 ++
 .../spi/loaders/resources/ZipResource.java    |  41 ++
 .../velocity/spi/methods/LangMethod.java      |  24 +
 .../velocity/spi/parsers/TemplateParser.java  |  43 ++
 .../spi/translators/CompiledTranslator.java   |  49 ++
 .../translators/InterpretedTranslator.java    |  35 ++
 .../translators/templates/BaseTemplate.java   | 140 +++++
 .../templates/CompiledTemplate.java           |  36 ++
 .../templates/CompiledVisitor.java            | 547 ++++++++++++++++++
 .../templates/InterpretedTemplate.java        |  47 ++
 .../templates/InterpretedVisitor.java         |  37 ++
 .../org/apache/velocity/util/ClassUtils.java  |  15 +-
 .../util/DeprecationAwareExtProperties.java   |   3 +-
 .../spi/compilers/JavacCompilerTest.java      |  12 +
 .../spi/compilers/JavassistCompilerTest.java  |  12 +
 .../spi/loaders/ClasspathLoaderTest.java      |  32 +
 .../translators/CompiledTranslatorTest.java   |  62 ++
 51 files changed, 3059 insertions(+), 9 deletions(-)
 create mode 100644 velocity-engine-core/README.md
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/api/Node.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/api/Resource.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/api/Template.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/Cache.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/Compiler.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/Converter.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/Loader.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/Parser.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/Translator.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/caches/MapCache.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/compilers/BaseCompiler.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/compilers/JavacCompiler.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/compilers/JavassistCompiler.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/converters/MultiConverter.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/converters/XssConverter.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/BaseLoader.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/ClasspathLoader.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/DataSourceLoader.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/FileLoader.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/JarLoader.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/MultiLoader.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/UrlLoader.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/ZipLoader.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/BaseResource.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/ClasspathResource.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/DataSourceResource.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/FileResource.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/InputStreamResource.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/JarResource.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/StringResource.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/UrlResource.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/ZipResource.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/methods/LangMethod.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/parsers/TemplateParser.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/CompiledTranslator.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/InterpretedTranslator.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/BaseTemplate.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/CompiledTemplate.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/CompiledVisitor.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/InterpretedTemplate.java
 create mode 100644 velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/InterpretedVisitor.java
 create mode 100644 velocity-engine-core/src/test/java/org/apache/velocity/spi/compilers/JavacCompilerTest.java
 create mode 100644 velocity-engine-core/src/test/java/org/apache/velocity/spi/compilers/JavassistCompilerTest.java
 create mode 100644 velocity-engine-core/src/test/java/org/apache/velocity/spi/loaders/ClasspathLoaderTest.java
 create mode 100644 velocity-engine-core/src/test/java/org/apache/velocity/spi/translators/CompiledTranslatorTest.java

diff --git a/pom.xml b/pom.xml
index 4432c60c3..2aa90db7b 100644
--- a/pom.xml
+++ b/pom.xml
@@ -137,6 +137,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.8.1</version>
                 <configuration>
                     <showDeprecation>true</showDeprecation>
                     <showWarning>true</showWarning>
diff --git a/velocity-engine-core/README.md b/velocity-engine-core/README.md
new file mode 100644
index 000000000..162762ecc
--- /dev/null
+++ b/velocity-engine-core/README.md
@@ -0,0 +1,62 @@
+```
+        +----------+                             |
+        |          |  nowContext  +---------+    |
+        |          | -----------> | Context | <--+ render
+   init |          |              +---------+    |
+  ----->| Velocity |                             v
+        |          |  getTemplate  +------------------+
+        |          | ------------> |     Template     |
+        |          |               +------------------+
+        +----------+
+```
+
+```java
+import java.io.StringReader;
+import java.io.Writer;
+import org.apache.velocity.Template;
+import org.apache.velocity.spi.Translator;
+import org.apache.velocity.runtime.parser.Parser;
+import org.apache.velocity.runtime.parser.node.SimpleNode;
+import org.apache.velocity.runtime.resource.Resource;
+import org.apache.velocity.runtime.resource.ResourceManager;
+import org.apache.velocity.runtime.resource.loader.ResourceLoader;
+
+public class View {
+
+  /**
+   * render the template
+   *
+   * @param name template name
+   * @param writer out
+   */
+  public void render(String name, Writer writer) {
+    // 1. get template
+    Template template = Velocity.getTemplate(name, "utf-8");
+    // 2. get current context
+    Context context = Velocity.nowContext();
+    // 3. render template
+    template.render(context, writer);
+  }
+}
+
+public class Velocity {
+
+  private ResourceManager resourceManager;
+  private Parser parser;
+  private Translator translator;
+  private ResourceLoader loader;
+
+  public Template getTemplate(String name, String encoding) {
+    String path = toPath(name);
+    Resource resource = resourceManager.getResource(path, ResourceManager.RESOURCE_TEMPLATE, encoding);
+    SimpleNode node = parser.parse(new StringReader((String) resource.getData()), new Template());
+    return translator.translate(resource, node);
+  }
+
+  private String toPath(String name) {
+    return "suffix/" + name;
+  }
+
+}
+
+```
diff --git a/velocity-engine-core/pom.xml b/velocity-engine-core/pom.xml
index bec9c9a51..95bbeb079 100644
--- a/velocity-engine-core/pom.xml
+++ b/velocity-engine-core/pom.xml
@@ -295,6 +295,12 @@
     </build>
 
     <dependencies>
+        <dependency>
+            <groupId>org.javassist</groupId>
+            <artifactId>javassist</artifactId>
+            <version>3.28.0-GA</version>
+            <scope>provided</scope>
+        </dependency>
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/api/Node.java b/velocity-engine-core/src/main/java/org/apache/velocity/api/Node.java
new file mode 100644
index 000000000..dfa63acbb
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/api/Node.java
@@ -0,0 +1,8 @@
+package org.apache.velocity.api;
+
+import org.apache.velocity.runtime.visitor.BaseVisitor;
+
+public interface Node {
+
+  void accept(BaseVisitor visitor);
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/api/Resource.java b/velocity-engine-core/src/main/java/org/apache/velocity/api/Resource.java
new file mode 100644
index 000000000..0873a5284
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/api/Resource.java
@@ -0,0 +1,99 @@
+package org.apache.velocity.api;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.Reader;
+import java.util.Locale;
+import org.apache.velocity.runtime.RuntimeInstance;
+
+public interface Resource {
+
+  /**
+   * Get the resource name.
+   *
+   * @return name
+   */
+  String getName();
+
+  /**
+   * Get the resource encoding.
+   *
+   * @return encoding
+   */
+  String getEncoding();
+
+  /**
+   * Get the resource locale.
+   *
+   * @return locale
+   */
+  Locale getLocale();
+
+  /**
+   * Get the resource last modified time.
+   *
+   * @return last modified time
+   */
+  long getLastModified();
+
+  /**
+   * Get the resource length.
+   *
+   * @return source length
+   */
+  long getLength();
+
+  /**
+   * Get the template source.
+   *
+   * @return source
+   * @throws IOException - If an I/O error occurs
+   */
+  String getSource() throws IOException;
+
+  /**
+   * Get the template source reader.
+   * <p/>
+   * NOTE: Don't forget close the reader.
+   * <p/>
+   * <pre>
+   * Reader reader = resource.openReader();
+   * try {
+   * 	 // do something ...
+   * } finally {
+   * 	 reader.close();
+   * }
+   * </pre>
+   *
+   * @return source reader
+   * @throws IOException - If an I/O error occurs
+   */
+  Reader openReader() throws IOException;
+
+  /**
+   * Get the template source input stream.
+   * <p/>
+   * NOTE: Don't forget close the input stream.
+   * <p/>
+   * <pre>
+   * InputStream stream = resource.openStream();
+   * try {
+   * 	 // do something ...
+   * } finally {
+   * 	 stream.close();
+   * }
+   * </pre>
+   *
+   * @return source input stream
+   * @throws IOException - If an I/O error occurs
+   */
+  InputStream openStream() throws IOException;
+
+  /**
+   * Get the template engine.
+   *
+   * @return engine
+   */
+  RuntimeInstance getEngine();
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/api/Template.java b/velocity-engine-core/src/main/java/org/apache/velocity/api/Template.java
new file mode 100644
index 000000000..ccf87f811
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/api/Template.java
@@ -0,0 +1,13 @@
+package org.apache.velocity.api;
+
+import java.io.IOException;
+import java.io.Writer;
+import java.text.ParseException;
+import org.apache.velocity.context.Context;
+
+public interface Template extends Resource, Node {
+
+  void render(Context context, Writer out) throws IOException, ParseException;
+
+  Object evaluate(Context context) throws ParseException;
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/app/VelocityEngine.java b/velocity-engine-core/src/main/java/org/apache/velocity/app/VelocityEngine.java
index 93751f3a7..2d5295038 100644
--- a/velocity-engine-core/src/main/java/org/apache/velocity/app/VelocityEngine.java
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/app/VelocityEngine.java
@@ -19,6 +19,10 @@
  * under the License.
  */
 
+import java.io.Reader;
+import java.io.Writer;
+import java.util.Objects;
+import java.util.Properties;
 import org.apache.velocity.Template;
 import org.apache.velocity.context.Context;
 import org.apache.velocity.exception.MethodInvocationException;
@@ -28,10 +32,6 @@
 import org.apache.velocity.runtime.RuntimeInstance;
 import org.slf4j.Logger;
 
-import java.io.Reader;
-import java.io.Writer;
-import java.util.Properties;
-
 /**
  * <p>
  * This class provides a separate new-able instance of the
@@ -51,14 +51,19 @@
  */
 public class VelocityEngine implements RuntimeConstants
 {
-    private RuntimeInstance ri = new RuntimeInstance();
+    private final RuntimeInstance ri;
 
     /**
      *  Init-less CTOR
      */
     public VelocityEngine()
     {
-        // do nothing
+        this(new RuntimeInstance());
+    }
+
+    public VelocityEngine(RuntimeInstance ri) // for testable
+    {
+        this.ri = Objects.requireNonNull(ri, "RuntimeInstance is null");
     }
 
     /**
@@ -68,6 +73,7 @@ public VelocityEngine()
      */
     public VelocityEngine(String propsFilename)
     {
+        this();
         ri.setProperties(propsFilename);
     }
 
@@ -77,6 +83,7 @@ public VelocityEngine(String propsFilename)
      */
     public VelocityEngine(Properties p)
     {
+        this();
         ri.setProperties(p);
     }
 
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/Cache.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/Cache.java
new file mode 100644
index 000000000..0ebb8d996
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/Cache.java
@@ -0,0 +1,25 @@
+package org.apache.velocity.spi;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.util.concurrent.ConcurrentMap;
+
+public interface Cache<K, V> extends ConcurrentMap<K, V> {
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/Compiler.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/Compiler.java
new file mode 100644
index 000000000..656781200
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/Compiler.java
@@ -0,0 +1,28 @@
+package org.apache.velocity.spi;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import org.apache.velocity.exception.VelocityException;
+
+public interface Compiler {
+
+  Class<?> compile(String source) throws VelocityException;
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/Converter.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/Converter.java
new file mode 100644
index 000000000..4a38ee538
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/Converter.java
@@ -0,0 +1,25 @@
+package org.apache.velocity.spi;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+public interface Converter {
+
+  String convert(String key, String value);
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/Loader.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/Loader.java
new file mode 100644
index 000000000..9cf1c953f
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/Loader.java
@@ -0,0 +1,31 @@
+package org.apache.velocity.spi;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import java.util.Locale;
+import org.apache.velocity.api.Resource;
+
+public interface Loader {
+
+  boolean exists(String name, Locale locale);
+
+  Resource load(String name, Locale locale, String encoding) throws IOException;
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/Parser.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/Parser.java
new file mode 100644
index 000000000..dac0cd6db
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/Parser.java
@@ -0,0 +1,29 @@
+package org.apache.velocity.spi;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+
+import org.apache.velocity.runtime.parser.ParseException;
+import org.apache.velocity.runtime.parser.node.SimpleNode;
+
+public interface Parser {
+
+  SimpleNode parse(String name, String source) throws ParseException;
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/Translator.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/Translator.java
new file mode 100644
index 000000000..f3b86483d
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/Translator.java
@@ -0,0 +1,29 @@
+package org.apache.velocity.spi;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import org.apache.velocity.api.Resource;
+import org.apache.velocity.api.Template;
+import org.apache.velocity.runtime.parser.node.SimpleNode;
+
+public interface Translator {
+
+  Template translate(Resource resource, SimpleNode root);
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/caches/MapCache.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/caches/MapCache.java
new file mode 100644
index 000000000..839ce74aa
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/caches/MapCache.java
@@ -0,0 +1,116 @@
+package org.apache.velocity.spi.caches;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.util.Collection;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+import org.apache.velocity.spi.Cache;
+
+public class MapCache<K, V> implements Cache<K, V> {
+
+  private final ConcurrentMap<K, V> map;
+
+  public MapCache() {
+    this.map = new ConcurrentHashMap<>();
+  }
+
+  @Override
+  public int size() {
+    return map.size();
+  }
+
+  @Override
+  public boolean isEmpty() {
+    return map.isEmpty();
+  }
+
+  @Override
+  public boolean containsKey(Object key) {
+    return map.containsKey(key);
+  }
+
+  @Override
+  public boolean containsValue(Object value) {
+    return map.containsValue(value);
+  }
+
+  @Override
+  public V get(Object key) {
+    return map.get(key);
+  }
+
+  @Override
+  public V put(K key, V value) {
+    return map.put(key, value);
+  }
+
+  @Override
+  public V remove(Object key) {
+    return map.remove(key);
+  }
+
+  @Override
+  public void putAll(Map<? extends K, ? extends V> m) {
+    map.putAll(m);
+  }
+
+  @Override
+  public void clear() {
+    map.clear();
+  }
+
+  @Override
+  public Set<K> keySet() {
+    return map.keySet();
+  }
+
+  @Override
+  public Collection<V> values() {
+    return map.values();
+  }
+
+  @Override
+  public Set<Entry<K, V>> entrySet() {
+    return map.entrySet();
+  }
+
+  @Override
+  public V putIfAbsent(K key, V value) {
+    return map.putIfAbsent(key, value);
+  }
+
+  @Override
+  public boolean remove(Object key, Object value) {
+    return map.remove(key, value);
+  }
+
+  @Override
+  public boolean replace(K key, V oldValue, V newValue) {
+    return map.replace(key, oldValue, newValue);
+  }
+
+  @Override
+  public V replace(K key, V value) {
+    return map.replace(key, value);
+  }
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/compilers/BaseCompiler.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/compilers/BaseCompiler.java
new file mode 100644
index 000000000..5cc551618
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/compilers/BaseCompiler.java
@@ -0,0 +1,111 @@
+package org.apache.velocity.spi.compilers;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.text.ParseException;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import org.apache.commons.lang3.StringUtils;
+import org.apache.velocity.exception.VelocityException;
+import org.apache.velocity.spi.Cache;
+import org.apache.velocity.spi.Compiler;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public abstract class BaseCompiler implements Compiler {
+
+  private static final Pattern PACKAGE_PATTERN = Pattern.compile("package\\s+([_a-zA-Z][_a-zA-Z0-9\\.]*);");
+  private static final Pattern CLASS_PATTERN = Pattern.compile("class\\s+([_a-zA-Z][_a-zA-Z0-9]*)\\s+");
+
+  protected final Logger logger = LoggerFactory.getLogger(getClass());
+  protected Cache<String, Object> cache;
+  protected File compileDirectory;
+  private volatile boolean first = true;
+
+  @Override
+  public Class<?> compile(String code) throws VelocityException {
+    String className = null;
+    try {
+      code = code.trim();
+      if (!code.endsWith("}")) {
+        throw new ParseException("The java code not endsWith \"}\"", code.length() - 1);
+      }
+      Matcher matcher = PACKAGE_PATTERN.matcher(code);
+      String pkg;
+      if (matcher.find()) {
+        pkg = matcher.group(1);
+      } else {
+        pkg = "";
+      }
+      matcher = CLASS_PATTERN.matcher(code);
+      String classSimpleName;
+      if (matcher.find()) {
+        classSimpleName = matcher.group(1);
+      } else {
+        throw new VelocityException("No such class name in java code.");
+      }
+      className = StringUtils.isNotEmpty(pkg) ? pkg + "." + classSimpleName : classSimpleName;
+      return doCompile(className, code);
+    } catch (Throwable t) {
+      if (logger != null && logger.isErrorEnabled()) {
+        logger.error("Failed to compile class, cause: " + t.getMessage() + ", class: " + className
+            + ", code: \n================================\n" + code + "\n================================\n", t);
+      }
+      if (t instanceof VelocityException) {
+        throw (VelocityException) t;
+      }
+      throw new VelocityException(
+          "Failed to compile class, cause: " + t.getMessage() + ", class: " + className + ", stack: ", t);
+    }
+  }
+
+  protected abstract Class<?> doCompile(String name, String source) throws Exception;
+
+  public void setCache(Cache<String, Object> cache) {
+    this.cache = cache;
+  }
+
+  protected void saveBytecode(String name, byte[] bytecode) {
+    if (compileDirectory != null) {
+      try {
+        File file = new File(compileDirectory, name.replace('.', '/') + ".class");
+        FileOutputStream out = new FileOutputStream(file);
+        try {
+          out.write(bytecode);
+          out.flush();
+        } finally {
+          out.close();
+        }
+        if (first) {
+          first = false;
+          if (logger != null && logger.isInfoEnabled()) {
+            logger.info("Compile template classes to directory " + compileDirectory.getAbsolutePath());
+          }
+        }
+      } catch (IOException e) {
+        logger.warn(e.getMessage(), e);
+      }
+    }
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/compilers/JavacCompiler.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/compilers/JavacCompiler.java
new file mode 100644
index 000000000..a69f0c6f3
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/compilers/JavacCompiler.java
@@ -0,0 +1,306 @@
+package org.apache.velocity.spi.compilers;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.net.URI;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.security.AccessController;
+import java.security.PrivilegedAction;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import javax.tools.DiagnosticCollector;
+import javax.tools.FileObject;
+import javax.tools.ForwardingJavaFileManager;
+import javax.tools.JavaCompiler;
+import javax.tools.JavaFileManager;
+import javax.tools.JavaFileObject;
+import javax.tools.JavaFileObject.Kind;
+import javax.tools.SimpleJavaFileObject;
+import javax.tools.StandardJavaFileManager;
+import javax.tools.StandardLocation;
+import javax.tools.ToolProvider;
+import org.apache.velocity.util.ClassUtils;
+
+public class JavacCompiler extends BaseCompiler {
+
+  private final JavaCompiler compiler;
+  private final DiagnosticCollector<JavaFileObject> diagnosticCollector;
+  private final StandardJavaFileManager standardJavaFileManager;
+  private final ClassLoaderImpl classLoader;
+  private final JavaFileManagerImpl javaFileManager;
+  private final List<String> options = new ArrayList<>();
+  private final List<String> lintOptions = new ArrayList<>();
+
+  public JavacCompiler() {
+    compiler = ToolProvider.getSystemJavaCompiler();
+    if (compiler == null) {
+      throw new IllegalStateException(
+          "Can not get system java compiler.");
+    }
+    diagnosticCollector = new DiagnosticCollector<JavaFileObject>();
+    standardJavaFileManager = compiler.getStandardFileManager(diagnosticCollector, null, null);
+    ClassLoader contextLoader = Thread.currentThread().getContextClassLoader();
+    try {
+      contextLoader.loadClass(JavacCompiler.class.getName());
+    } catch (ClassNotFoundException e) {
+      contextLoader = JavacCompiler.class.getClassLoader();
+    }
+    ClassLoader loader = contextLoader;
+    Set<File> files = new HashSet<>();
+    while (loader instanceof URLClassLoader
+        && (!loader.getClass().getName().equals("sun.misc.Launcher$AppClassLoader"))) {
+      URLClassLoader urlClassLoader = (URLClassLoader) loader;
+      for (URL url : urlClassLoader.getURLs()) {
+        files.add(new File(url.getFile()));
+      }
+      loader = loader.getParent();
+    }
+    if (files.size() > 0) {
+      try {
+        Iterable<? extends File> list = standardJavaFileManager.getLocation(StandardLocation.CLASS_PATH);
+        for (File file : list) {
+          files.add(file);
+        }
+        standardJavaFileManager.setLocation(StandardLocation.CLASS_PATH, files);
+      } catch (IOException e) {
+        throw new IllegalStateException(e.getMessage(), e);
+      }
+    }
+    final ClassLoader parentLoader = contextLoader;
+    classLoader = AccessController.doPrivileged(new PrivilegedAction<ClassLoaderImpl>() {
+      public ClassLoaderImpl run() {
+        return new ClassLoaderImpl(parentLoader);
+      }
+    });
+    javaFileManager = new JavaFileManagerImpl(standardJavaFileManager, classLoader);
+    lintOptions.add("-Xlint:unchecked");
+  }
+
+  @Override
+  protected Class<?> doCompile(String name, String source) throws Exception {
+    return doCompile(name, source, options);
+  }
+
+  private Class<?> doCompile(String name, String sourceCode, List<String> options) throws Exception {
+    try {
+      return classLoader.loadClass(name);
+    } catch (ClassNotFoundException e) {
+      int i = name.lastIndexOf('.');
+      String packageName = i < 0 ? "" : name.substring(0, i);
+      String className = i < 0 ? name : name.substring(i + 1);
+      JavaFileObjectImpl javaFileObject = new JavaFileObjectImpl(className, sourceCode);
+      javaFileManager.putFileForInput(StandardLocation.SOURCE_PATH, packageName,
+          className + ClassUtils.JAVA_EXTENSION, javaFileObject);
+      Boolean result = compiler.getTask(
+          null,
+          javaFileManager,
+          diagnosticCollector,
+          options,
+          null,
+          Collections.singletonList(javaFileObject)
+      ).call();
+      if (result == null || !result) {
+        throw new IllegalStateException(
+            "Compilation failed. class: " + name + ", diagnostics: " + diagnosticCollector.getDiagnostics());
+      }
+      if (compileDirectory != null) {
+        saveBytecode(name, javaFileObject.getByteCode());
+      }
+      return classLoader.loadClass(name);
+    }
+  }
+
+  private static final class JavaFileObjectImpl extends SimpleJavaFileObject {
+
+    private final CharSequence source;
+    private ByteArrayOutputStream bytecode;
+
+    public JavaFileObjectImpl(final String baseName, final CharSequence source) {
+      super(ClassUtils.toURI(baseName + ClassUtils.JAVA_EXTENSION), Kind.SOURCE);
+      this.source = source;
+    }
+
+    public JavaFileObjectImpl(final String name, final Kind kind) {
+      super(ClassUtils.toURI(name), kind);
+      source = null;
+    }
+
+    public JavaFileObjectImpl(URI uri, Kind kind) {
+      super(uri, kind);
+      source = null;
+    }
+
+    @Override
+    public CharSequence getCharContent(final boolean ignoreEncodingErrors) throws UnsupportedOperationException {
+      if (source == null) {
+        throw new UnsupportedOperationException("source == null");
+      }
+      return source;
+    }
+
+    @Override
+    public InputStream openInputStream() {
+      return new ByteArrayInputStream(getByteCode());
+    }
+
+    @Override
+    public OutputStream openOutputStream() {
+      return bytecode = new ByteArrayOutputStream();
+    }
+
+    public byte[] getByteCode() {
+      return bytecode.toByteArray();
+    }
+  }
+
+  private static final class JavaFileManagerImpl extends ForwardingJavaFileManager<JavaFileManager> {
+
+    private final ClassLoaderImpl classLoader;
+    private final Map<URI, JavaFileObject> fileObjects = new HashMap<URI, JavaFileObject>();
+
+    public JavaFileManagerImpl(JavaFileManager fileManager, ClassLoaderImpl classLoader) {
+      super(fileManager);
+      this.classLoader = classLoader;
+    }
+
+    @Override
+    public FileObject getFileForInput(Location location, String packageName, String relativeName) throws IOException {
+      FileObject o = fileObjects.get(uri(location, packageName, relativeName));
+      if (o != null) {
+        return o;
+      }
+      return super.getFileForInput(location, packageName, relativeName);
+    }
+
+    @Override
+    public JavaFileObject getJavaFileForOutput(Location location, String qualifiedName, Kind kind, FileObject fo)
+        throws IOException {
+      JavaFileObject file = new JavaFileObjectImpl(qualifiedName, kind);
+      classLoader.add(qualifiedName, file);
+      return file;
+    }
+
+    @Override
+    public ClassLoader getClassLoader(JavaFileManager.Location location) {
+      return classLoader;
+    }
+
+    @Override
+    public String inferBinaryName(Location loc, JavaFileObject file) {
+      if (file instanceof JavaFileObjectImpl) {
+        return file.getName();
+      }
+      return super.inferBinaryName(loc, file);
+    }
+
+    @Override
+    public Iterable<JavaFileObject> list(Location location, String packageName, Set<Kind> kinds, boolean recurse)
+        throws IOException {
+      ArrayList<JavaFileObject> files = new ArrayList<JavaFileObject>();
+      if (location == StandardLocation.CLASS_PATH && kinds.contains(JavaFileObject.Kind.CLASS)) {
+        for (JavaFileObject file : fileObjects.values()) {
+          if (file.getKind() == Kind.CLASS && file.getName().startsWith(packageName)) {
+            files.add(file);
+          }
+        }
+        files.addAll(classLoader.files());
+      } else if (location == StandardLocation.SOURCE_PATH && kinds.contains(JavaFileObject.Kind.SOURCE)) {
+        for (JavaFileObject file : fileObjects.values()) {
+          if (file.getKind() == Kind.SOURCE && file.getName().startsWith(packageName)) {
+            files.add(file);
+          }
+        }
+      }
+      Iterable<JavaFileObject> result = super.list(location, packageName, kinds, recurse);
+      for (JavaFileObject file : result) {
+        files.add(file);
+      }
+      return files;
+    }
+
+    public void putFileForInput(StandardLocation location, String packageName, String relativeName,
+        JavaFileObject file) {
+      fileObjects.put(uri(location, packageName, relativeName), file);
+    }
+
+    private URI uri(Location location, String packageName, String relativeName) {
+      return ClassUtils.toURI(location.getName() + '/' + packageName + '/' + relativeName);
+    }
+
+  }
+
+  private static final class ClassLoaderImpl extends ClassLoader {
+
+    private final Map<String, JavaFileObject> classes = new HashMap<String, JavaFileObject>();
+
+    ClassLoaderImpl(final ClassLoader parentClassLoader) {
+      super(parentClassLoader);
+    }
+
+    Collection<JavaFileObject> files() {
+      return Collections.unmodifiableCollection(classes.values());
+    }
+
+    @Override
+    protected Class<?> findClass(final String qualifiedClassName) throws ClassNotFoundException {
+      try {
+        return super.findClass(qualifiedClassName);
+      } catch (ClassNotFoundException e) {
+        JavaFileObject file = classes.get(qualifiedClassName);
+        if (file != null) {
+          byte[] bytes = ((JavaFileObjectImpl) file).getByteCode();
+          return defineClass(qualifiedClassName, bytes, 0, bytes.length);
+        }
+        throw e;
+      }
+    }
+
+    @Override
+    public InputStream getResourceAsStream(final String name) {
+      if (name.endsWith(ClassUtils.CLASS_EXTENSION)) {
+        String qualifiedClassName = name.substring(0, name.length() - ClassUtils.CLASS_EXTENSION.length())
+            .replace('/', '.');
+        JavaFileObjectImpl file = (JavaFileObjectImpl) classes.get(qualifiedClassName);
+        if (file != null) {
+          return new ByteArrayInputStream(file.getByteCode());
+        }
+      }
+      return super.getResourceAsStream(name);
+    }
+
+    public void add(final String qualifiedClassName, final JavaFileObject javaFile) {
+      classes.put(qualifiedClassName, javaFile);
+    }
+
+  }
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/compilers/JavassistCompiler.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/compilers/JavassistCompiler.java
new file mode 100644
index 000000000..5eba7a175
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/compilers/JavassistCompiler.java
@@ -0,0 +1,30 @@
+package org.apache.velocity.spi.compilers;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import javassist.ClassPool;
+
+public class JavassistCompiler extends BaseCompiler {
+
+  @Override
+  protected Class<?> doCompile(String name, String source) throws Exception {
+    return ClassPool.getDefault().makeClass(source).toClass();
+  }
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/converters/MultiConverter.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/converters/MultiConverter.java
new file mode 100644
index 000000000..a7b4bd5df
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/converters/MultiConverter.java
@@ -0,0 +1,42 @@
+package org.apache.velocity.spi.converters;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import org.apache.velocity.spi.Converter;
+
+public class MultiConverter implements Converter {
+
+  private Converter[] converters;
+
+  @Override
+  public String convert(String key, String value) {
+    if (converters == null) {
+      return value;
+    }
+    for (Converter converter : converters) {
+      value = converter.convert(key, value);
+    }
+    return value;
+  }
+
+  public void setConverters(Converter[] converters) {
+    this.converters = converters;
+  }
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/converters/XssConverter.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/converters/XssConverter.java
new file mode 100644
index 000000000..ade359df8
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/converters/XssConverter.java
@@ -0,0 +1,68 @@
+package org.apache.velocity.spi.converters;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import org.apache.commons.lang3.StringUtils;
+import org.apache.velocity.spi.Converter;
+
+public class XssConverter implements Converter {
+
+  @Override
+  public String convert(String key, String value) {
+    if (StringUtils.isBlank(value)) {
+      return value;
+    }
+    char[] array = value.toCharArray();
+    int length = array.length;
+    StringBuilder out = new StringBuilder(length);
+    int i = 0;
+    while (i < length) {
+      char ch = array[i++];
+      switch (ch) {
+        case '>': {
+          out.append("&gt;");
+          break;
+        }
+        case '<': {
+          out.append("&lt;");
+          break;
+        }
+        case '\"': {
+          out.append("&quot;");
+          break;
+        }
+        case '\'': {
+          out.append("&apos;");
+          break;
+        }
+        case '&': {
+          out.append("&amp;");
+          break;
+        }
+        default: {
+          out.append(ch);
+          break;
+        }
+      }
+    }
+    return out.toString();
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/BaseLoader.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/BaseLoader.java
new file mode 100644
index 000000000..fb7b1809c
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/BaseLoader.java
@@ -0,0 +1,153 @@
+package org.apache.velocity.spi.loaders;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import java.util.Locale;
+import org.apache.commons.lang3.StringUtils;
+import org.apache.velocity.api.Resource;
+import org.apache.velocity.runtime.RuntimeInstance;
+import org.apache.velocity.spi.Loader;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public abstract class BaseLoader implements Loader {
+
+  protected final Logger logger = LoggerFactory.getLogger(getClass());
+  protected RuntimeInstance engine;
+  protected String encoding;
+  protected Locale locale;
+  protected boolean reloadable;
+  protected String[] templateDirectory; // 模板目录
+  protected String[] templateSuffix;    // 模板后缀
+
+  @Override
+  public boolean exists(String name, Locale locale) {
+    Locale cur = locale;
+    while (cur != null) {
+      if (_exists(name, locale, toPath(name, cur))) {
+        return true;
+      }
+      cur = getParentLocale(cur);
+    }
+    return _exists(name, locale, toPath(name, null));
+  }
+
+  @Override
+  public Resource load(String name, Locale locale, String encoding) throws IOException {
+    if (StringUtils.isBlank(encoding)) {
+      encoding = this.encoding;
+    }
+    Locale cur = locale;
+    String path = toPath(name, cur);
+    while (cur != null && !_exists(name, locale, path)) {
+      cur = getParentLocale(cur);
+      path = toPath(name, cur);
+    }
+    return doLoad(name, locale, encoding, path);
+  }
+
+  protected abstract boolean doExists(String name, Locale locale, String path) throws IOException;
+
+  protected abstract Resource doLoad(String name, Locale locale, String encoding, String path) throws IOException;
+
+  private boolean _exists(String name, Locale locale, String path) {
+    try {
+      return doExists(name, locale, path);
+    } catch (Exception e) {
+      return false;
+    }
+  }
+
+  protected String toPath(String name, Locale locale) {
+    if (endsWith(name, templateSuffix)) {
+      name = relocate(name, locale, templateDirectory);
+    }
+    return appendLocale(name, locale);
+  }
+
+  protected String relocate(String name, Locale locale, String[] directories) {
+    if (directories != null && directories.length > 0) {
+      for (String directory : directories) {
+        try {
+          if (doExists(name, locale, directory + name)) {
+            return directory + name;
+          }
+        } catch (IOException ignore) {
+          continue;
+        }
+      }
+      return directories[0] + name;
+    }
+    return name;
+  }
+
+  private static boolean endsWith(String value, String[] suffixes) {
+    if (suffixes == null || suffixes.length == 0) {
+      return false;
+    }
+    for (String suffix : suffixes) {
+      if (StringUtils.endsWith(value, suffix)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  private static String appendLocale(String name, Locale locale) {
+    if (locale == null) {
+      return name;
+    }
+    return locale + name;
+  }
+
+  private static Locale getParentLocale(Locale locale) {
+    return null;
+  }
+
+  // region setter
+
+  public void setEngine(RuntimeInstance engine) {
+    this.engine = engine;
+  }
+
+  public void setEncoding(String encoding) {
+    this.encoding = encoding;
+  }
+
+  public void setLocale(Locale locale) {
+    this.locale = locale;
+  }
+
+  public void setReloadable(boolean reloadable) {
+    this.reloadable = reloadable;
+  }
+
+  public void setTemplateDirectory(String[] templateDirectory) {
+    this.templateDirectory = templateDirectory;
+  }
+
+  public void setTemplateSuffix(String[] templateSuffix) {
+    this.templateSuffix = templateSuffix;
+  }
+
+  // endregion setter
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/ClasspathLoader.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/ClasspathLoader.java
new file mode 100644
index 000000000..30890ac24
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/ClasspathLoader.java
@@ -0,0 +1,39 @@
+package org.apache.velocity.spi.loaders;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import java.util.Locale;
+import org.apache.velocity.api.Resource;
+import org.apache.velocity.spi.loaders.resources.ClasspathResource;
+
+public class ClasspathLoader extends BaseLoader {
+
+  @Override
+  protected boolean doExists(String name, Locale locale, String path) throws IOException {
+    return Thread.currentThread().getContextClassLoader().getResource(path) != null;
+  }
+
+  @Override
+  protected Resource doLoad(String name, Locale locale, String encoding, String path) throws IOException {
+    return new ClasspathResource(engine, name, locale, encoding, path);
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/DataSourceLoader.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/DataSourceLoader.java
new file mode 100644
index 000000000..bb817e7b0
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/DataSourceLoader.java
@@ -0,0 +1,39 @@
+package org.apache.velocity.spi.loaders;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import java.util.Locale;
+import org.apache.velocity.api.Resource;
+import org.apache.velocity.spi.loaders.resources.DataSourceResource;
+
+public class DataSourceLoader extends BaseLoader {
+
+  @Override
+  protected boolean doExists(String name, Locale locale, String path) throws IOException {
+    return false;
+  }
+
+  @Override
+  protected Resource doLoad(String name, Locale locale, String encoding, String path) throws IOException {
+    return new DataSourceResource(engine, name, locale, encoding, 0);
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/FileLoader.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/FileLoader.java
new file mode 100644
index 000000000..6e04ecf81
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/FileLoader.java
@@ -0,0 +1,40 @@
+package org.apache.velocity.spi.loaders;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+
+import java.io.IOException;
+import java.util.Locale;
+import org.apache.velocity.api.Resource;
+import org.apache.velocity.spi.loaders.resources.FileResource;
+
+public class FileLoader extends BaseLoader {
+
+  @Override
+  protected boolean doExists(String name, Locale locale, String path) throws IOException {
+    return false;
+  }
+
+  @Override
+  protected Resource doLoad(String name, Locale locale, String encoding, String path) throws IOException {
+    return new FileResource(engine, name, locale, encoding, path);
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/JarLoader.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/JarLoader.java
new file mode 100644
index 000000000..3f3ef37e1
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/JarLoader.java
@@ -0,0 +1,40 @@
+package org.apache.velocity.spi.loaders;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+
+import java.io.IOException;
+import java.util.Locale;
+import org.apache.velocity.api.Resource;
+import org.apache.velocity.spi.loaders.resources.JarResource;
+
+public class JarLoader extends BaseLoader {
+
+  @Override
+  protected boolean doExists(String name, Locale locale, String path) throws IOException {
+    return false;
+  }
+
+  @Override
+  protected Resource doLoad(String name, Locale locale, String encoding, String path) throws IOException {
+    return new JarResource(engine, name, locale, encoding, path);
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/MultiLoader.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/MultiLoader.java
new file mode 100644
index 000000000..bc365eb9c
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/MultiLoader.java
@@ -0,0 +1,66 @@
+package org.apache.velocity.spi.loaders;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.util.Locale;
+import org.apache.velocity.api.Resource;
+import org.apache.velocity.spi.Loader;
+
+public class MultiLoader implements Loader {
+
+  private Loader[] loaders;
+
+  @Override
+  public boolean exists(String name, Locale locale) {
+    if (loaders.length == 1) {
+      return loaders[0].exists(name, locale);
+    }
+    for (Loader loader : loaders) {
+      try {
+        if (loader.exists(name, locale)) {
+          return true;
+        }
+      } catch (Exception ignore) {
+      }
+    }
+    return false;
+  }
+
+  @Override
+  public Resource load(String name, Locale locale, String encoding) throws IOException {
+    for (Loader loader : loaders) {
+      try {
+        if (loader.exists(name, locale)) {
+          return loader.load(name, locale, encoding);
+        }
+      } catch (Exception ignore) {
+      }
+    }
+    throw new FileNotFoundException("No such template file: " + name);
+  }
+
+  public void setLoaders(Loader[] loaders) {
+    this.loaders = loaders;
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/UrlLoader.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/UrlLoader.java
new file mode 100644
index 000000000..f2dcba8f7
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/UrlLoader.java
@@ -0,0 +1,37 @@
+package org.apache.velocity.spi.loaders;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import java.util.Locale;
+import org.apache.velocity.api.Resource;
+
+public class UrlLoader extends BaseLoader {
+
+  @Override
+  protected boolean doExists(String name, Locale locale, String path) throws IOException {
+    return false;
+  }
+
+  @Override
+  protected Resource doLoad(String name, Locale locale, String encoding, String path) throws IOException {
+    return null;
+  }
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/ZipLoader.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/ZipLoader.java
new file mode 100644
index 000000000..69be77edc
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/ZipLoader.java
@@ -0,0 +1,37 @@
+package org.apache.velocity.spi.loaders;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import java.util.Locale;
+import org.apache.velocity.api.Resource;
+
+public class ZipLoader extends BaseLoader {
+
+  @Override
+  protected boolean doExists(String name, Locale locale, String path) throws IOException {
+    return false;
+  }
+
+  @Override
+  protected Resource doLoad(String name, Locale locale, String encoding, String path) throws IOException {
+    return null;
+  }
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/BaseResource.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/BaseResource.java
new file mode 100644
index 000000000..13f644abc
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/BaseResource.java
@@ -0,0 +1,84 @@
+package org.apache.velocity.spi.loaders.resources;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import java.io.Serializable;
+import java.util.Locale;
+import org.apache.commons.io.IOUtils;
+import org.apache.velocity.api.Resource;
+import org.apache.velocity.runtime.RuntimeInstance;
+
+public abstract class BaseResource implements Resource, Serializable {
+
+  private static final long serialVersionUID = 86551207664766539L;
+
+  private final transient RuntimeInstance engine;
+  private final String name;
+  private final String encoding;
+  private final Locale locale;
+  private final long lastModified;
+
+  public BaseResource(RuntimeInstance engine, String name, Locale locale, String encoding, long lastModified) {
+    this.engine = engine;
+    this.name = name;
+    this.encoding = encoding;
+    this.locale = locale;
+    this.lastModified = lastModified;
+  }
+
+  @Override
+  public String getName() {
+    return name;
+  }
+
+  @Override
+  public String getEncoding() {
+    return encoding;
+  }
+
+  @Override
+  public Locale getLocale() {
+    return locale;
+  }
+
+  @Override
+  public long getLastModified() {
+    return lastModified;
+  }
+
+  @Override
+  public long getLength() {
+    return -1;
+  }
+
+  @Override
+  public String getSource() throws IOException {
+    StringBuilder source = new StringBuilder();
+    IOUtils.copy(openReader(), source);
+    return source.toString();
+  }
+
+  @Override
+  public RuntimeInstance getEngine() {
+    return engine;
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/ClasspathResource.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/ClasspathResource.java
new file mode 100644
index 000000000..7122c22ba
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/ClasspathResource.java
@@ -0,0 +1,40 @@
+package org.apache.velocity.spi.loaders.resources;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Locale;
+import org.apache.velocity.runtime.RuntimeInstance;
+
+public class ClasspathResource extends InputStreamResource {
+
+  private static final long serialVersionUID = -8216061890256939202L;
+
+  public ClasspathResource(RuntimeInstance engine, String name, Locale locale, String encoding, String file) {
+    super(engine, name, locale, encoding, file);
+  }
+
+  @Override
+  public InputStream openStream() throws IOException {
+    return Thread.currentThread().getContextClassLoader().getResourceAsStream(getFile());
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/DataSourceResource.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/DataSourceResource.java
new file mode 100644
index 000000000..18955e410
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/DataSourceResource.java
@@ -0,0 +1,46 @@
+package org.apache.velocity.spi.loaders.resources;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.Reader;
+import java.util.Locale;
+import org.apache.velocity.runtime.RuntimeInstance;
+
+public class DataSourceResource extends BaseResource {
+
+  private static final long serialVersionUID = 5156212703341663975L;
+
+  public DataSourceResource(RuntimeInstance engine, String name, Locale locale, String encoding, long lastModified) {
+    super(engine, name, locale, encoding, lastModified);
+  }
+
+  @Override
+  public Reader openReader() throws IOException {
+    return null;
+  }
+
+  @Override
+  public InputStream openStream() throws IOException {
+    return null;
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/FileResource.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/FileResource.java
new file mode 100644
index 000000000..018fde6b0
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/FileResource.java
@@ -0,0 +1,41 @@
+package org.apache.velocity.spi.loaders.resources;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Locale;
+import org.apache.velocity.runtime.RuntimeInstance;
+
+public class FileResource extends InputStreamResource {
+
+  private static final long serialVersionUID = 3007762548080486248L;
+
+  public FileResource(RuntimeInstance engine, String name, Locale locale, String encoding, String file) {
+    super(engine, name, locale, encoding, file);
+  }
+
+  @Override
+  public InputStream openStream() throws IOException {
+    return new FileInputStream(getFile());
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/InputStreamResource.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/InputStreamResource.java
new file mode 100644
index 000000000..3b82e2583
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/InputStreamResource.java
@@ -0,0 +1,82 @@
+package org.apache.velocity.spi.loaders.resources;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.util.Locale;
+import org.apache.commons.lang3.StringUtils;
+import org.apache.velocity.runtime.RuntimeInstance;
+
+public abstract class InputStreamResource extends BaseResource {
+
+  private static final long serialVersionUID = 2729791474763118265L;
+
+  private final String file;
+
+  public InputStreamResource(RuntimeInstance engine, String name, Locale locale, String encoding, String file) {
+    this(engine, name, locale, encoding, -1, file);
+  }
+
+  public InputStreamResource(RuntimeInstance engine, String name, Locale locale, String encoding, long lastModified,
+      String file) {
+    super(engine, name, locale, encoding, lastModified);
+    this.file = file;
+  }
+
+  @Override
+  public long getLastModified() {
+    File f = new File(getFile());
+    if (f != null && f.exists()) {
+      return f.lastModified();
+    }
+    return super.getLastModified();
+  }
+
+  @Override
+  public long getLength() {
+    File f = new File(getFile());
+    if (f != null) {
+      return f.length();
+    }
+    return super.getLength();
+  }
+
+  @Override
+  public Reader openReader() throws IOException {
+    InputStream in = openStream();
+    if (in == null) {
+      throw new FileNotFoundException(
+          "Not found template " + getName() + " in " + getClass().getSimpleName() + ": " + file);
+    }
+    String encoding = getEncoding();
+    return StringUtils.isEmpty(encoding)
+        ? new InputStreamReader(in) : new InputStreamReader(in, encoding);
+  }
+
+  public String getFile() {
+    return file;
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/JarResource.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/JarResource.java
new file mode 100644
index 000000000..c52daca5e
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/JarResource.java
@@ -0,0 +1,42 @@
+package org.apache.velocity.spi.loaders.resources;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Locale;
+import java.util.jar.JarFile;
+import org.apache.velocity.runtime.RuntimeInstance;
+
+public class JarResource extends InputStreamResource {
+
+  private static final long serialVersionUID = 5777154748252092679L;
+
+  public JarResource(RuntimeInstance engine, String name, Locale locale, String encoding, String file) {
+    super(engine, name, locale, encoding, file);
+  }
+
+  @Override
+  public InputStream openStream() throws IOException {
+    JarFile jarFile = new JarFile(getFile());
+    return jarFile.getInputStream(jarFile.getJarEntry(getName()));
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/StringResource.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/StringResource.java
new file mode 100644
index 000000000..655284c0a
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/StringResource.java
@@ -0,0 +1,57 @@
+package org.apache.velocity.spi.loaders.resources;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.Reader;
+import java.io.StringReader;
+import java.util.Locale;
+import org.apache.commons.io.input.ReaderInputStream;
+import org.apache.velocity.runtime.RuntimeInstance;
+
+public class StringResource extends BaseResource {
+
+  private static final long serialVersionUID = -3908373765734849091L;
+
+  private final String source;
+
+  public StringResource(RuntimeInstance engine, String name, Locale locale, String encoding, long lastModified,
+      String source) {
+    super(engine, name, locale, encoding, lastModified);
+    this.source = source;
+  }
+
+  @Override
+  public Reader openReader() throws IOException {
+    return new StringReader(source);
+  }
+
+  @Override
+  public InputStream openStream() throws IOException {
+    return new ReaderInputStream(openReader(), getEncoding());
+  }
+
+  @Override
+  public long getLength() {
+    return source.length();
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/UrlResource.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/UrlResource.java
new file mode 100644
index 000000000..98ddd898a
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/UrlResource.java
@@ -0,0 +1,42 @@
+package org.apache.velocity.spi.loaders.resources;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+import java.util.Locale;
+import org.apache.velocity.runtime.RuntimeInstance;
+
+public class UrlResource extends InputStreamResource {
+
+  private static final long serialVersionUID = 6787846728614581583L;
+
+  public UrlResource(RuntimeInstance engine, String name, Locale locale, String encoding, String file) {
+    super(engine, name, locale, encoding, file);
+  }
+
+  @Override
+  public InputStream openStream() throws IOException {
+    URL url = new URL(getName());
+    return url.openStream();
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/ZipResource.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/ZipResource.java
new file mode 100644
index 000000000..2d4aa3363
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/loaders/resources/ZipResource.java
@@ -0,0 +1,41 @@
+package org.apache.velocity.spi.loaders.resources;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Locale;
+import java.util.zip.ZipFile;
+import org.apache.velocity.runtime.RuntimeInstance;
+
+public class ZipResource extends InputStreamResource {
+
+  private static final long serialVersionUID = -5614543506378211399L;
+
+  public ZipResource(RuntimeInstance engine, String name, Locale locale, String encoding, String file) {
+    super(engine, name, locale, encoding, file);
+  }
+
+  @Override
+  public InputStream openStream() throws IOException {
+    ZipFile zipFile = new ZipFile(getFile());
+    return zipFile.getInputStream(zipFile.getEntry(getName()));
+  }
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/methods/LangMethod.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/methods/LangMethod.java
new file mode 100644
index 000000000..e2322970d
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/methods/LangMethod.java
@@ -0,0 +1,24 @@
+package org.apache.velocity.spi.methods;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+public class LangMethod {
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/parsers/TemplateParser.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/parsers/TemplateParser.java
new file mode 100644
index 000000000..b7c94dc02
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/parsers/TemplateParser.java
@@ -0,0 +1,43 @@
+package org.apache.velocity.spi.parsers;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.StringReader;
+import org.apache.velocity.Template;
+import org.apache.velocity.runtime.parser.ParseException;
+import org.apache.velocity.runtime.parser.node.SimpleNode;
+import org.apache.velocity.spi.Parser;
+
+public class TemplateParser implements Parser {
+
+  private org.apache.velocity.runtime.parser.Parser innerParser;
+
+  @Override
+  public SimpleNode parse(String name, String source) throws ParseException {
+    Template template = new Template();
+    template.setName(name);
+    return innerParser.parse(new StringReader(source), template);
+  }
+
+  public void setInnerParser(org.apache.velocity.runtime.parser.Parser innerParser) {
+    this.innerParser = innerParser;
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/CompiledTranslator.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/CompiledTranslator.java
new file mode 100644
index 000000000..ecc49618c
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/CompiledTranslator.java
@@ -0,0 +1,49 @@
+package org.apache.velocity.spi.translators;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import org.apache.velocity.api.Resource;
+import org.apache.velocity.api.Template;
+import org.apache.velocity.exception.VelocityException;
+import org.apache.velocity.runtime.parser.node.SimpleNode;
+import org.apache.velocity.spi.Compiler;
+import org.apache.velocity.spi.Translator;
+import org.apache.velocity.spi.translators.templates.CompiledVisitor;
+
+public class CompiledTranslator implements Translator {
+
+  private Compiler compiler;
+
+  @Override
+  public Template translate(Resource resource, SimpleNode root) {
+    CompiledVisitor visitor = new CompiledVisitor();
+    String code = visitor.visit(root, resource);
+    try {
+      return (Template) compiler.compile(code).getConstructor().newInstance();
+    } catch (Throwable e) {
+      throw new VelocityException(e);
+    }
+  }
+
+  public void setCompiler(Compiler compiler) {
+    this.compiler = compiler;
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/InterpretedTranslator.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/InterpretedTranslator.java
new file mode 100644
index 000000000..5681b9d29
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/InterpretedTranslator.java
@@ -0,0 +1,35 @@
+package org.apache.velocity.spi.translators;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import org.apache.velocity.api.Resource;
+import org.apache.velocity.api.Template;
+import org.apache.velocity.runtime.parser.node.SimpleNode;
+import org.apache.velocity.spi.Translator;
+import org.apache.velocity.spi.translators.templates.InterpretedTemplate;
+
+public class InterpretedTranslator implements Translator {
+
+  @Override
+  public Template translate(Resource resource, SimpleNode root) {
+    return new InterpretedTemplate(resource, root, null);
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/BaseTemplate.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/BaseTemplate.java
new file mode 100644
index 000000000..dcd417bbd
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/BaseTemplate.java
@@ -0,0 +1,140 @@
+package org.apache.velocity.spi.translators.templates;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.Reader;
+import java.io.StringWriter;
+import java.io.Writer;
+import java.text.ParseException;
+import java.util.Locale;
+import org.apache.velocity.api.Resource;
+import org.apache.velocity.api.Template;
+import org.apache.velocity.context.Context;
+import org.apache.velocity.runtime.RuntimeInstance;
+import org.apache.velocity.runtime.parser.node.SimpleNode;
+import org.apache.velocity.runtime.visitor.BaseVisitor;
+
+public abstract class BaseTemplate implements Template {
+
+  private final Resource resource;
+  private final SimpleNode root;
+  private final Template parent;
+  private final String name;
+  private final String encoding;
+  private final Locale locale;
+  private final long lastModified;
+  private final long length;
+
+  public BaseTemplate(Resource resource, SimpleNode node, Template parent) {
+    this.resource = resource;
+    this.root = node;
+    this.parent = parent;
+    this.name = resource.getName();
+    this.encoding = resource.getEncoding();
+    this.locale = resource.getLocale();
+    this.lastModified = resource.getLastModified();
+    this.length = resource.getLength();
+  }
+
+  @Override
+  public void render(Context context, Writer out) throws IOException, ParseException {
+    try {
+      doRender(context, out);
+    } catch (IOException | ParseException e) {
+      throw e;
+    } catch (Exception e) {
+      throw new RuntimeException(e);
+    }
+  }
+
+  @Override
+  public Object evaluate(Context context) throws ParseException {
+    StringWriter writer = new StringWriter();
+    try {
+      render(context, writer);
+    } catch (IOException e) {
+      throw new RuntimeException(e);
+    }
+    return writer.toString();
+  }
+
+  @Override
+  public void accept(BaseVisitor visitor) {
+    visitor.visit(root, resource);
+  }
+
+  @Override
+  public String getName() {
+    return name;
+  }
+
+  @Override
+  public String getEncoding() {
+    return encoding;
+  }
+
+  @Override
+  public Locale getLocale() {
+    return locale;
+  }
+
+  @Override
+  public long getLastModified() {
+    return lastModified;
+  }
+
+  @Override
+  public long getLength() {
+    return length;
+  }
+
+  @Override
+  public String getSource() throws IOException {
+    return resource.getSource();
+  }
+
+  @Override
+  public Reader openReader() throws IOException {
+    return resource.openReader();
+  }
+
+  @Override
+  public InputStream openStream() throws IOException {
+    return resource.openStream();
+  }
+
+  @Override
+  public RuntimeInstance getEngine() {
+    return resource.getEngine();
+  }
+
+  public SimpleNode getRoot() {
+    return root;
+  }
+
+  public Template getParent() {
+    return parent;
+  }
+
+  protected abstract void doRender(Context context, Writer out) throws Exception;
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/CompiledTemplate.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/CompiledTemplate.java
new file mode 100644
index 000000000..6e4fe0101
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/CompiledTemplate.java
@@ -0,0 +1,36 @@
+package org.apache.velocity.spi.translators.templates;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import org.apache.velocity.api.Resource;
+import org.apache.velocity.api.Template;
+import org.apache.velocity.app.VelocityEngine;
+import org.apache.velocity.runtime.parser.node.SimpleNode;
+import org.apache.velocity.spi.Compiler;
+
+public abstract class CompiledTemplate extends BaseTemplate {
+
+  private Compiler compiler;
+
+  public CompiledTemplate(VelocityEngine engine, Resource resource, SimpleNode node, Template parent) {
+    super(resource, node, parent);
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/CompiledVisitor.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/CompiledVisitor.java
new file mode 100644
index 000000000..39f53682b
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/CompiledVisitor.java
@@ -0,0 +1,547 @@
+package org.apache.velocity.spi.translators.templates;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.math.BigDecimal;
+import java.math.BigInteger;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+import org.apache.commons.lang3.StringUtils;
+import org.apache.velocity.api.Resource;
+import org.apache.velocity.api.Template;
+import org.apache.velocity.runtime.parser.Token;
+import org.apache.velocity.runtime.parser.node.ASTAddNode;
+import org.apache.velocity.runtime.parser.node.ASTAndNode;
+import org.apache.velocity.runtime.parser.node.ASTAssignment;
+import org.apache.velocity.runtime.parser.node.ASTBlock;
+import org.apache.velocity.runtime.parser.node.ASTComment;
+import org.apache.velocity.runtime.parser.node.ASTDirective;
+import org.apache.velocity.runtime.parser.node.ASTDirectiveAssign;
+import org.apache.velocity.runtime.parser.node.ASTDivNode;
+import org.apache.velocity.runtime.parser.node.ASTEQNode;
+import org.apache.velocity.runtime.parser.node.ASTElseIfStatement;
+import org.apache.velocity.runtime.parser.node.ASTElseStatement;
+import org.apache.velocity.runtime.parser.node.ASTEscape;
+import org.apache.velocity.runtime.parser.node.ASTEscapedDirective;
+import org.apache.velocity.runtime.parser.node.ASTExpression;
+import org.apache.velocity.runtime.parser.node.ASTFalse;
+import org.apache.velocity.runtime.parser.node.ASTFloatingPointLiteral;
+import org.apache.velocity.runtime.parser.node.ASTGENode;
+import org.apache.velocity.runtime.parser.node.ASTGTNode;
+import org.apache.velocity.runtime.parser.node.ASTIdentifier;
+import org.apache.velocity.runtime.parser.node.ASTIfStatement;
+import org.apache.velocity.runtime.parser.node.ASTIncludeStatement;
+import org.apache.velocity.runtime.parser.node.ASTIndex;
+import org.apache.velocity.runtime.parser.node.ASTIntegerLiteral;
+import org.apache.velocity.runtime.parser.node.ASTIntegerRange;
+import org.apache.velocity.runtime.parser.node.ASTLENode;
+import org.apache.velocity.runtime.parser.node.ASTLTNode;
+import org.apache.velocity.runtime.parser.node.ASTMap;
+import org.apache.velocity.runtime.parser.node.ASTMethod;
+import org.apache.velocity.runtime.parser.node.ASTModNode;
+import org.apache.velocity.runtime.parser.node.ASTMulNode;
+import org.apache.velocity.runtime.parser.node.ASTNENode;
+import org.apache.velocity.runtime.parser.node.ASTNegateNode;
+import org.apache.velocity.runtime.parser.node.ASTNotNode;
+import org.apache.velocity.runtime.parser.node.ASTObjectArray;
+import org.apache.velocity.runtime.parser.node.ASTOrNode;
+import org.apache.velocity.runtime.parser.node.ASTParameters;
+import org.apache.velocity.runtime.parser.node.ASTReference;
+import org.apache.velocity.runtime.parser.node.ASTSetDirective;
+import org.apache.velocity.runtime.parser.node.ASTStringLiteral;
+import org.apache.velocity.runtime.parser.node.ASTSubtractNode;
+import org.apache.velocity.runtime.parser.node.ASTText;
+import org.apache.velocity.runtime.parser.node.ASTTextblock;
+import org.apache.velocity.runtime.parser.node.ASTTrue;
+import org.apache.velocity.runtime.parser.node.ASTVariable;
+import org.apache.velocity.runtime.parser.node.ASTWord;
+import org.apache.velocity.runtime.parser.node.ASTprocess;
+import org.apache.velocity.runtime.parser.node.Node;
+import org.apache.velocity.runtime.parser.node.NodeUtils;
+import org.apache.velocity.runtime.parser.node.SimpleNode;
+import org.apache.velocity.runtime.visitor.BaseVisitor;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class CompiledVisitor extends BaseVisitor {
+
+  private final Logger logger = LoggerFactory.getLogger(getClass());
+  private final StringBuilder codeBuilder = new StringBuilder(1024 * 8);
+
+  private String[] staticImportPackages = new String[]{"org.apache.velocity.spi.methods.LangMethod"};
+  private String[] importPackages;
+  private int ident = 2;
+
+  @Override
+  public Object visit(ASTAssignment node, Object data) {
+    return null;
+  }
+
+  @Override
+  public Object visit(ASTComment node, Object data) {
+    return "";
+  }
+
+  @Override
+  public Object visit(ASTDirective node, Object data) {
+    // TODO: 2021/11/23
+    return "";
+  }
+
+  @Override
+  public Object visit(ASTDirectiveAssign node, Object data) {
+    return null;
+  }
+
+  @Override
+  public Object visit(ASTSetDirective node, Object data) {
+    // https://velocity.apache.org/engine/1.7/user-guide.html#set
+    // lhs:
+    //  1. a variable reference
+    //  2. a property reference
+    // rhs:
+    //  1. Variable reference
+    //  2. String literal
+    //  3. Property reference
+    //  4. Method reference
+    //  5. Number literal
+    //  6. ArrayList
+    //  7. Map
+    //  #set( $monkey = $bill )                                         ## variable reference
+    //  #set( $monkey.Friend = "monica" )                               ## string literal
+    //  #set( $monkey.Blame = $hello.Leak )                             ## property reference
+    //  #set( $monkey.Plan = $hello.weave($web) )                       ## method reference
+    //  #set( $monkey.Number = 123 )                                    ## number literal
+    //  #set( $monkey.Say = ["Not", $my, "fault"] )                     ## ArrayList
+    //  #set( $monkey.Map = {"banana" : "good", "roast beef" : "bad"})  ## Map
+
+    String key = (String) dispatch(node.jjtGetChild(0), (Resource) data);
+    Object val = dispatch(node.jjtGetChild(1), (Resource) data);
+    return "$context.put(\"" + key + "\"," + val + ");";
+  }
+
+  @Override
+  public String visit(ASTExpression node, Object data) {
+    return (String) dispatch(node.jjtGetChild(0), (Resource) data);
+  }
+
+  @Override
+  public String visit(ASTReference node, Object data) {
+    // There are three types of references in the VTL: variables, properties and methods.
+    // https://velocity.apache.org/engine/1.7/user-guide.html#references
+    // 1. Variables
+    // 2. Properties
+    // 3. Methods
+    return null;
+  }
+
+  @Override
+  public Object visit(ASTBlock node, Object data) {
+    int k = node.jjtGetNumChildren();
+    Resource resource = (Resource) data;
+    StringBuilder block = new StringBuilder();
+    for (int i = 0; i < k; i++) {
+      block.append(dispatch(node.jjtGetChild(i), resource)).append("\r\n");
+    }
+    return block.toString().trim();
+  }
+
+  // region if/elseif/else
+
+  @Override
+  public Object visit(ASTIfStatement node, Object data) {
+    /*
+     *  if () {         // child:0
+     *    xx            // child:1
+     *  } else if () {  // child:2
+     *    yy            //
+     *  } else {
+     *    zz            // child:3
+     *  }
+     */
+    int k = node.jjtGetNumChildren();
+    Resource resource = (Resource) data;
+    String cond = (String) dispatch(node.jjtGetChild(0), resource);
+    String then = (String) dispatch(node.jjtGetChild(1), resource);
+    StringBuilder ifStmt = new StringBuilder();
+    ifStmt.append(append(ident, "if (")).append(cond).append(") {\r\n");
+    ifStmt.append(append(ident + 2, then)).append("\r\n");
+    ifStmt.append(append(ident, "}"));
+    if (k > 2) {
+      // else if
+      for (int i = 2; i < k; i++) {
+        ifStmt.append(dispatch(node.jjtGetChild(i), resource));
+      }
+    }
+    return ifStmt.toString();
+  }
+
+  @Override
+  public Object visit(ASTElseIfStatement node, Object data) {
+    String cond = (String) dispatch(node.jjtGetChild(0), (Resource) data);
+    String then = (String) dispatch(node.jjtGetChild(1), (Resource) data);
+    return append(1, "else if (") + cond + ") {\n"
+        + append(ident + 2, then) + "\r\n"
+        + append(ident, "}");
+  }
+
+  @Override
+  public Object visit(ASTElseStatement node, Object data) {
+    String then = (String) dispatch(node.jjtGetChild(0), (Resource) data);
+    return append(1, "else {\r\n")
+        + append(ident + 2, then) + "\r\n"
+        + append(ident, "}");
+  }
+
+  // endregion if/elseif/else
+
+  // region binaryOperator
+
+  // region comparison
+
+  @Override
+  public String visit(ASTNENode node, Object data) {
+    Object lhs = dispatch(node.jjtGetChild(0), (Resource) data);
+    Object rhs = dispatch(node.jjtGetChild(1), (Resource) data);
+    return "!java.util.Objects.equals(" + lhs + ", " + rhs + ")";
+  }
+
+  @Override
+  public String visit(ASTEQNode node, Object data) {
+    Object lhs = dispatch(node.jjtGetChild(0), (Resource) data);
+    Object rhs = dispatch(node.jjtGetChild(1), (Resource) data);
+    return "java.util.Objects.equals(" + lhs + ", " + rhs + ")";
+  }
+
+  @Override
+  public String visit(ASTGENode node, Object data) {
+    String lhs = (String) dispatch(node.jjtGetChild(0), (Resource) data);
+    String rhs = (String) dispatch(node.jjtGetChild(1), (Resource) data);
+    return lhs + " >= " + rhs;
+  }
+
+  @Override
+  public String visit(ASTGTNode node, Object data) {
+    String lhs = (String) dispatch(node.jjtGetChild(0), (Resource) data);
+    String rhs = (String) dispatch(node.jjtGetChild(1), (Resource) data);
+    return lhs + " > " + rhs;
+  }
+
+  @Override
+  public String visit(ASTLENode node, Object data) {
+    String lhs = (String) dispatch(node.jjtGetChild(0), (Resource) data);
+    String rhs = (String) dispatch(node.jjtGetChild(1), (Resource) data);
+    return lhs + " <= " + rhs;
+  }
+
+  @Override
+  public String visit(ASTLTNode node, Object data) {
+    String lhs = (String) dispatch(node.jjtGetChild(0), (Resource) data);
+    String rhs = (String) dispatch(node.jjtGetChild(1), (Resource) data);
+    return lhs + " < " + rhs;
+  }
+
+  // endregion comparison
+
+  // region logical
+
+  @Override
+  public Object visit(ASTAndNode node, Object data) {
+    String lhs = (String) dispatch(node.jjtGetChild(0), (Resource) data);
+    String rhs = (String) dispatch(node.jjtGetChild(1), (Resource) data);
+    return lhs + " && " + rhs;
+  }
+
+  @Override
+  public Object visit(ASTOrNode node, Object data) {
+    String lhs = (String) dispatch(node.jjtGetChild(0), (Resource) data);
+    String rhs = (String) dispatch(node.jjtGetChild(1), (Resource) data);
+    return lhs + " || " + rhs;
+  }
+
+  @Override
+  public Object visit(ASTNotNode node, Object data) {
+    String mhs = (String) dispatch(node.jjtGetChild(0), (Resource) data);
+    return "!" + mhs;
+  }
+
+  // endregion logical
+
+  // region math
+
+  @Override
+  public Object visit(ASTAddNode node, Object data) {
+    String lhs = (String) dispatch(node.jjtGetChild(0), (Resource) data);
+    String rhs = (String) dispatch(node.jjtGetChild(1), (Resource) data);
+    return lhs + " + " + rhs;
+  }
+
+  @Override
+  public Object visit(ASTDivNode node, Object data) {
+    String lhs = (String) dispatch(node.jjtGetChild(0), (Resource) data);
+    String rhs = (String) dispatch(node.jjtGetChild(1), (Resource) data);
+    return lhs + " / " + rhs;
+  }
+
+  @Override
+  public Object visit(ASTModNode node, Object data) {
+    String lhs = (String) dispatch(node.jjtGetChild(0), (Resource) data);
+    String rhs = (String) dispatch(node.jjtGetChild(1), (Resource) data);
+    return lhs + " % " + rhs;
+  }
+
+  @Override
+  public Object visit(ASTMulNode node, Object data) {
+    String lhs = (String) dispatch(node.jjtGetChild(0), (Resource) data);
+    String rhs = (String) dispatch(node.jjtGetChild(1), (Resource) data);
+    return lhs + " * " + rhs;
+  }
+
+  @Override
+  public Object visit(ASTSubtractNode node, Object data) {
+    String lhs = (String) dispatch(node.jjtGetChild(0), (Resource) data);
+    String rhs = (String) dispatch(node.jjtGetChild(1), (Resource) data);
+    return lhs + " - " + rhs;
+  }
+
+  // endregion math
+
+  // endregion binaryOperator
+
+  // region literal
+
+  @Override
+  public String visit(ASTStringLiteral node, Object data) {
+    return "\"" + node.getFirstToken().image.substring(1, node.getFirstToken().image.length() - 1) + "\"";
+  }
+
+  @Override
+  public BigInteger visit(ASTIntegerLiteral node, Object data) {
+    return new BigInteger(node.getFirstToken().image);
+  }
+
+  @Override
+  public BigDecimal visit(ASTFloatingPointLiteral node, Object data) {
+    return new BigDecimal(node.getFirstToken().image);
+  }
+
+  // endregion literal
+
+  @Override
+  public String visit(ASTText node, Object data) {
+    Token t = node.getFirstToken();
+    List<String> text = new ArrayList<>();
+    for (; t != node.getLastToken(); t = t.next) {
+      text.add(StringUtils.trim(NodeUtils.tokenLiteral(node.getParser(), t)));
+    }
+    text.add(StringUtils.trim(NodeUtils.tokenLiteral(node.getParser(), t)));
+    return text.stream()
+        .filter(StringUtils::isNotBlank)
+        .map(s -> "    $output.write(\"" + s + "\");")
+        .collect(Collectors.joining("\r\n"));
+  }
+
+  /**
+   * <pre>
+   * {@code
+   *    package xxx;
+   *
+   *    import yyy.y.y.y;
+   *    import zzz.z.z.z;
+   *
+   *    public final class Template_$name_$locale_$encoding extends Template {
+   *
+   *      private final VelocityEngine engine;
+   *
+   *      @Override
+   *      public boolean render(Context $context, Writer $writer) throws Exception {
+   *        writer.write(xx)
+   *        return true;
+   *      }
+   *    }
+   *
+   * }
+   * </pre>
+   *
+   * @return Template
+   */
+  @Override
+  public String visit(SimpleNode node, Object data) {
+    int i, k = node.jjtGetNumChildren();
+    Resource resource = (Resource) data;
+    StringBuilder sourceCode = new StringBuilder();
+    StringBuilder methodCode = new StringBuilder();
+
+    for (i = 0; i < k; i++) {
+      methodCode.append(dispatch(node.jjtGetChild(i), resource)).append("\r\n");
+    }
+
+    String pkgName = CompiledTemplate.class.getPackage().getName();
+    String clsName = getTemplateClassName(resource);
+
+    methodCode.append(this.codeBuilder);
+    sourceCode.append("package ").append(pkgName).append(";\r\n\r\n");
+    Arrays.stream(staticImportPackages).map(s -> "import static " + s + ".*;\r\n").forEach(sourceCode::append);
+    sourceCode.append("\r\n");
+    sourceCode.append("public final class ").append(clsName).append(" extends CompiledTemplate {\r\n\r\n");
+    sourceCode.append("  @Override\r\n");
+    sourceCode.append("  protected void doRender(Context $context, Writer $output) throws Exception {\r\n");
+    sourceCode.append("    ").append("").append("\r\n");
+    sourceCode.append("  }\r\n");
+    sourceCode.append("}\r\n");
+    String clazz = sourceCode.toString();
+    logger.debug(clazz);
+    return clazz;
+  }
+
+  private Object dispatch(Node node, Resource resource) {
+    if (node instanceof ASTAssignment) {
+      return visit((ASTAssignment) node, resource);
+    }
+    // region BinaryOperator Comparison
+    else if (node instanceof ASTNENode) {
+      return visit((ASTNENode) node, resource);
+    } else if (node instanceof ASTEQNode) {
+      return visit((ASTEQNode) node, resource);
+    } else if (node instanceof ASTGENode) {
+      return visit((ASTGENode) node, resource);
+    } else if (node instanceof ASTGTNode) {
+      return visit((ASTGTNode) node, resource);
+    } else if (node instanceof ASTLENode) {
+      return visit((ASTLENode) node, resource);
+    } else if (node instanceof ASTLTNode) {
+      return visit((ASTLTNode) node, resource);
+    }
+    // endregion BinaryOperator Comparison
+
+    // region BinaryOperator Logical
+    else if (node instanceof ASTAndNode) {
+      return visit((ASTAndNode) node, resource);
+    } else if (node instanceof ASTOrNode) {
+      return visit((ASTOrNode) node, resource);
+    }
+    // endregion BinaryOperator Logical
+
+    // region BinaryOperator Math
+    else if (node instanceof ASTAddNode) {
+      return visit((ASTAddNode) node, resource);
+    } else if (node instanceof ASTDivNode) {
+      return visit((ASTDivNode) node, resource);
+    } else if (node instanceof ASTModNode) {
+      return visit((ASTModNode) node, resource);
+    } else if (node instanceof ASTMulNode) {
+      return visit((ASTMulNode) node, resource);
+    } else if (node instanceof ASTSubtractNode) {
+      return visit((ASTSubtractNode) node, resource);
+    }
+    // endregion BinaryOperator Math
+
+    else if (node instanceof ASTBlock) {
+      return visit((ASTBlock) node, resource);
+    } else if (node instanceof ASTComment) {
+      return visit((ASTComment) node, resource);
+    } else if (node instanceof ASTDirective) {
+      return visit((ASTDirective) node, resource);
+    } else if (node instanceof ASTDirectiveAssign) {
+      return visit((ASTDirectiveAssign) node, resource);
+    } else if (node instanceof ASTElseIfStatement) {
+      return visit((ASTElseIfStatement) node, resource);
+    } else if (node instanceof ASTElseStatement) {
+      return visit((ASTElseStatement) node, resource);
+    } else if (node instanceof ASTEscape) {
+      return visit((ASTEscape) node, resource);
+    } else if (node instanceof ASTEscapedDirective) {
+      return visit((ASTEscapedDirective) node, resource);
+    } else if (node instanceof ASTExpression) {
+      return visit((ASTExpression) node, resource);
+    } else if (node instanceof ASTFalse) {
+      return visit((ASTFalse) node, resource);
+    } else if (node instanceof ASTFloatingPointLiteral) {
+      return visit((ASTFloatingPointLiteral) node, resource);
+    } else if (node instanceof ASTIntegerLiteral) {
+      return visit((ASTIntegerLiteral) node, resource);
+    } else if (node instanceof ASTStringLiteral) {
+      return visit((ASTStringLiteral) node, resource);
+    } else if (node instanceof ASTIdentifier) {
+      return visit((ASTIdentifier) node, resource);
+    } else if (node instanceof ASTIfStatement) {
+      return visit((ASTIfStatement) node, resource);
+    } else if (node instanceof ASTIncludeStatement) {
+      return visit((ASTIncludeStatement) node, resource);
+    } else if (node instanceof ASTIndex) {
+      return visit((ASTIndex) node, resource);
+    } else if (node instanceof ASTIntegerRange) {
+      return visit((ASTIntegerRange) node, resource);
+    } else if (node instanceof ASTMap) {
+      return visit((ASTMap) node, resource);
+    } else if (node instanceof ASTMethod) {
+      return visit((ASTMethod) node, resource);
+    } else if (node instanceof ASTNegateNode) {
+      return visit((ASTNegateNode) node, resource);
+    } else if (node instanceof ASTNotNode) {
+      return visit((ASTNotNode) node, resource);
+    } else if (node instanceof ASTObjectArray) {
+      return visit((ASTObjectArray) node, resource);
+    } else if (node instanceof ASTParameters) {
+      return visit((ASTParameters) node, resource);
+    } else if (node instanceof ASTprocess) {
+      return visit((ASTprocess) node, resource);
+    } else if (node instanceof ASTReference) {
+      return visit((ASTReference) node, resource);
+    } else if (node instanceof ASTSetDirective) {
+      return visit((ASTSetDirective) node, resource);
+    } else if (node instanceof ASTText) {
+      return visit((ASTText) node, resource);
+    } else if (node instanceof ASTTextblock) {
+      return visit((ASTTextblock) node, resource);
+    } else if (node instanceof ASTTrue) {
+      return visit((ASTTrue) node, resource);
+    } else if (node instanceof ASTVariable) {
+      return visit((ASTVariable) node, resource);
+    } else if (node instanceof ASTWord) {
+      return visit((ASTWord) node, resource);
+    } else {
+      throw new IllegalArgumentException("unknown node:" + node);
+    }
+  }
+
+  private String getTemplateClassName(Resource resource) {
+    // Template_name_locale_encoding
+    StringBuilder name = new StringBuilder();
+    name.append(Template.class.getSimpleName());
+    name.append("_");
+    name.append(resource.getName());
+    if (resource.getLocale() != null) {
+      name.append("_");
+      name.append(resource.getLocale());
+    }
+    if (StringUtils.isNotBlank(resource.getEncoding())) {
+      name.append("_");
+      name.append(resource.getEncoding());
+    }
+    return name.toString().replaceAll("[-.]", "_");
+  }
+
+  private String append(int ident, String s) {
+    return StringUtils.repeat(' ', ident) + s;
+  }
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/InterpretedTemplate.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/InterpretedTemplate.java
new file mode 100644
index 000000000..f67e18836
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/InterpretedTemplate.java
@@ -0,0 +1,47 @@
+package org.apache.velocity.spi.translators.templates;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.Writer;
+import org.apache.velocity.api.Resource;
+import org.apache.velocity.api.Template;
+import org.apache.velocity.context.Context;
+import org.apache.velocity.context.InternalContextAdapterImpl;
+import org.apache.velocity.runtime.parser.node.SimpleNode;
+
+public class InterpretedTemplate extends BaseTemplate {
+
+  public InterpretedTemplate(Resource resource, SimpleNode node, Template parent) {
+    super(resource, node, parent);
+  }
+
+  @Override
+  protected void doRender(Context context, Writer out) throws Exception {
+    InternalContextAdapterImpl ctx = new InternalContextAdapterImpl(context);
+    InterpretedVisitor visitor = new InterpretedVisitor();
+    visitor.setWriter(out);
+    visitor.setContext(ctx);
+
+    getRoot().init(ctx, getEngine());
+
+    accept(visitor);
+  }
+
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/InterpretedVisitor.java b/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/InterpretedVisitor.java
new file mode 100644
index 000000000..1a07c422d
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/spi/translators/templates/InterpretedVisitor.java
@@ -0,0 +1,37 @@
+package org.apache.velocity.spi.translators.templates;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import java.io.IOException;
+import org.apache.velocity.exception.VelocityException;
+import org.apache.velocity.runtime.parser.node.SimpleNode;
+import org.apache.velocity.runtime.visitor.BaseVisitor;
+
+public class InterpretedVisitor extends BaseVisitor {
+
+  @Override
+  public Object visit(SimpleNode node, Object data) {
+    try {
+      return node.render(context, writer);
+    } catch (IOException e) {
+      throw new VelocityException(e);
+    }
+  }
+}
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/util/ClassUtils.java b/velocity-engine-core/src/main/java/org/apache/velocity/util/ClassUtils.java
index 34ddf5564..175bc9361 100644
--- a/velocity-engine-core/src/main/java/org/apache/velocity/util/ClassUtils.java
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/util/ClassUtils.java
@@ -19,6 +19,9 @@
  * under the License.
  */
 
+import java.io.InputStream;
+import java.net.URI;
+import java.net.URISyntaxException;
 import org.apache.velocity.context.InternalContextAdapter;
 import org.apache.velocity.exception.MethodInvocationException;
 import org.apache.velocity.exception.VelocityException;
@@ -28,8 +31,6 @@
 import org.apache.velocity.util.introspection.IntrospectionCacheData;
 import org.apache.velocity.util.introspection.VelMethod;
 
-import java.io.InputStream;
-
 
 
 /**
@@ -42,6 +43,9 @@
  */
 public class ClassUtils {
 
+    public static final String CLASS_EXTENSION = ".class";
+    public static final String JAVA_EXTENSION = ".java";
+
     /**
      * Utility class; cannot be instantiated.
      */
@@ -268,4 +272,11 @@ public static VelMethod getMethod(String methodName, Object[] params,
         return method;
     }
 
+    public static URI toURI(String name) {
+        try {
+            return new URI(name);
+        } catch (URISyntaxException e) {
+            throw new RuntimeException(e);
+        }
+    }
 }
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/util/DeprecationAwareExtProperties.java b/velocity-engine-core/src/main/java/org/apache/velocity/util/DeprecationAwareExtProperties.java
index a67454a5d..bccf36310 100644
--- a/velocity-engine-core/src/main/java/org/apache/velocity/util/DeprecationAwareExtProperties.java
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/util/DeprecationAwareExtProperties.java
@@ -103,7 +103,8 @@ protected String translateKey(String key)
      */
     public Object get(String key)
     {
-        return super.get(translateKey(key));
+        key = translateKey(key);
+        return super.get(key);
     }
 
     /**
diff --git a/velocity-engine-core/src/test/java/org/apache/velocity/spi/compilers/JavacCompilerTest.java b/velocity-engine-core/src/test/java/org/apache/velocity/spi/compilers/JavacCompilerTest.java
new file mode 100644
index 000000000..b1f8dd0de
--- /dev/null
+++ b/velocity-engine-core/src/test/java/org/apache/velocity/spi/compilers/JavacCompilerTest.java
@@ -0,0 +1,12 @@
+package org.apache.velocity.spi.compilers;
+
+import org.junit.Test;
+
+public class JavacCompilerTest {
+
+  @Test
+  public void test_compile() {
+    JavacCompiler compiler = new JavacCompiler();
+  }
+
+}
diff --git a/velocity-engine-core/src/test/java/org/apache/velocity/spi/compilers/JavassistCompilerTest.java b/velocity-engine-core/src/test/java/org/apache/velocity/spi/compilers/JavassistCompilerTest.java
new file mode 100644
index 000000000..e07da608a
--- /dev/null
+++ b/velocity-engine-core/src/test/java/org/apache/velocity/spi/compilers/JavassistCompilerTest.java
@@ -0,0 +1,12 @@
+package org.apache.velocity.spi.compilers;
+
+import org.junit.Test;
+
+public class JavassistCompilerTest {
+
+  @Test
+  public void test_compile() {
+    JavacCompiler compiler = new JavacCompiler();
+  }
+
+}
diff --git a/velocity-engine-core/src/test/java/org/apache/velocity/spi/loaders/ClasspathLoaderTest.java b/velocity-engine-core/src/test/java/org/apache/velocity/spi/loaders/ClasspathLoaderTest.java
new file mode 100644
index 000000000..b6d2b121e
--- /dev/null
+++ b/velocity-engine-core/src/test/java/org/apache/velocity/spi/loaders/ClasspathLoaderTest.java
@@ -0,0 +1,32 @@
+package org.apache.velocity.spi.loaders;
+
+import java.io.IOException;
+import java.io.Reader;
+import java.util.Locale;
+import org.apache.velocity.api.Resource;
+import org.apache.velocity.runtime.RuntimeInstance;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class ClasspathLoaderTest {
+
+  @Test
+  public void test_load() {
+    ClasspathLoader loader = new ClasspathLoader();
+    RuntimeInstance runtimeInstance = new RuntimeInstance();
+    runtimeInstance.init();
+    loader.setEngine(runtimeInstance);
+    loader.setEncoding("utf-8");
+    loader.setLocale(Locale.getDefault());
+    loader.setReloadable(true);
+    loader.setTemplateSuffix(new String[]{".vm"});
+    loader.setTemplateDirectory(new String[]{"evaluate/"});
+    try {
+      Resource resource = loader.load("eval1.vm", null, null);
+      try (Reader reader = resource.openReader()) {
+      }
+    } catch (IOException e) {
+      Assert.fail(e.getMessage());
+    }
+  }
+}
diff --git a/velocity-engine-core/src/test/java/org/apache/velocity/spi/translators/CompiledTranslatorTest.java b/velocity-engine-core/src/test/java/org/apache/velocity/spi/translators/CompiledTranslatorTest.java
new file mode 100644
index 000000000..8285f037a
--- /dev/null
+++ b/velocity-engine-core/src/test/java/org/apache/velocity/spi/translators/CompiledTranslatorTest.java
@@ -0,0 +1,62 @@
+package org.apache.velocity.spi.translators;
+
+import java.io.IOException;
+import java.io.Reader;
+import java.util.Locale;
+import org.apache.velocity.api.Resource;
+import org.apache.velocity.runtime.RuntimeInstance;
+import org.apache.velocity.runtime.parser.ParseException;
+import org.apache.velocity.spi.Loader;
+import org.apache.velocity.spi.Parser;
+import org.apache.velocity.spi.compilers.JavassistCompiler;
+import org.apache.velocity.spi.loaders.ClasspathLoader;
+import org.apache.velocity.spi.parsers.TemplateParser;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class CompiledTranslatorTest {
+
+  @Test
+  public void test_translate() {
+    RuntimeInstance runtimeInstance = new RuntimeInstance();
+    runtimeInstance.init();
+    Loader loader = creatLoader(runtimeInstance);
+    Parser parser = createParser(runtimeInstance);
+
+    CompiledTranslator translator = new CompiledTranslator();
+    translator.setCompiler(new JavassistCompiler());
+    Resource resource;
+    String res;
+    try {
+      resource = loader.load("eval1.vm", null, null);
+      try (Reader reader = resource.openReader()) {
+        StringBuilder out = new StringBuilder();
+        int ch;
+        while ((ch = reader.read()) != -1) {
+          out.append((char) ch);
+        }
+        res = out.toString();
+      }
+      translator.translate(resource, parser.parse("eval1.vm", res));
+    } catch (IOException | ParseException e) {
+      Assert.fail(e.getMessage());
+    }
+  }
+
+  private Parser createParser(RuntimeInstance runtimeInstance) {
+    TemplateParser parser = new TemplateParser();
+    parser.setInnerParser(runtimeInstance.createNewParser());
+    return parser;
+  }
+
+  private Loader creatLoader(RuntimeInstance runtimeInstance) {
+    ClasspathLoader loader = new ClasspathLoader();
+    loader.setEngine(runtimeInstance);
+    loader.setEncoding("utf-8");
+    loader.setLocale(Locale.getDefault());
+    loader.setReloadable(true);
+    loader.setTemplateSuffix(new String[]{".vm"});
+    loader.setTemplateDirectory(new String[]{"evaluate/"});
+    return loader;
+  }
+}