diff --git a/pljava-so/build.xml b/pljava-so/build.xml
index d57b45543..93e1620d5 100644
--- a/pljava-so/build.xml
+++ b/pljava-so/build.xml
@@ -80,7 +80,9 @@
 			</filterchain>
 		</loadresource>
 
-		<script language="javascript"><![CDATA[
+		<script
+			language="javascript"
+			classpathref="maven.plugin.classpath"><![CDATA[
 			var msvc_version = parseInt(project.getProperty('MSVC_VER'));
 			var knows_rint = project.getProperty('KNOWS_MSVC_RINT');
 			if (msvc_version >= 1800  && knows_rint === null) {
diff --git a/pljava-so/pom.xml b/pljava-so/pom.xml
index d22da81d5..7a8b9fac5 100644
--- a/pljava-so/pom.xml
+++ b/pljava-so/pom.xml
@@ -272,6 +272,65 @@
 				<pgsql.pgconfig>pg_config</pgsql.pgconfig>
 			</properties>
 		</profile>
+
+		<profile>
+			<id>hasjavah</id>
+			<activation>
+				<jdk>[1.6,10)</jdk>
+			</activation>
+			<properties>
+				<javah.include>${basedir}/target/nar/javah-include/</javah.include>
+			</properties>
+			<build>
+				<plugins>
+					<plugin>
+						<groupId>com.github.maven-nar</groupId>
+						<artifactId>nar-maven-plugin</artifactId>
+						<configuration>
+							<!-- Generates C header files from Java class files. -->
+							<javah>
+								<classPaths>
+									<classPath>${basedir}/../pljava/target/classes/</classPath>
+									<classPath>${basedir}/../pljava-api/target/classes/</classPath>
+								</classPaths>
+								<classDirectory>${basedir}/../pljava/target/classes/</classDirectory>
+								<extraClasses>
+									<extraClass>java.sql.Types</extraClass>
+								</extraClasses>
+							</javah>
+						</configuration>
+					</plugin>
+				</plugins>
+			</build>
+		</profile>
+
+		<profile>
+			<id>lacksjavah</id>
+			<activation>
+				<jdk>[10,)</jdk>
+			</activation>
+			<properties>
+				<javah.include>${basedir}/../pljava/target/javah-include/</javah.include>
+			</properties>
+			<build>
+				<plugins>
+					<plugin>
+						<groupId>com.github.maven-nar</groupId>
+						<artifactId>nar-maven-plugin</artifactId>
+						<configuration>
+							<c>
+								<includePaths combine.children='append'>
+									<includePath>${basedir}/src/main/include/fallback/jdbc</includePath>
+								</includePaths>
+							</c>
+							<java>
+								<include>true</include>
+							</java>
+						</configuration>
+					</plugin>
+				</plugins>
+			</build>
+		</profile>
 	</profiles>
 
 	<build>
@@ -301,7 +360,9 @@
 						</goals>
 						<configuration>
 							<target>
-								<script language='javascript'>
+								<script
+									language='javascript'
+									classpathref='maven.plugin.classpath'>
 <![CDATA[
 /* This regex supports a function to wrap a string in the quoting needed for a
    C string literal. Capturing group 1 captures those special characters that
@@ -380,7 +441,9 @@ if ( null !== jvmdflt )
 
 								<!-- Converts pg_config output
 									 to "pgsql.properties" -->
-								<ant />
+								<ant>
+									<reference refid='maven.plugin.classpath'/>
+								</ant>
 							</target>
 						</configuration>
 					</execution>
@@ -419,17 +482,6 @@ if ( null !== jvmdflt )
 
 				<configuration>
 					<maxCores>${nar.cores}</maxCores>
-					<!-- Generates C header files from Java class files. -->
-					<javah>
-						<classPaths>
-							<classPath>${basedir}/../pljava/target/classes/</classPath>
-							<classPath>${basedir}/../pljava-api/target/classes/</classPath>
-						</classPaths>
-						<classDirectory>${basedir}/../pljava/target/classes/</classDirectory>
-						<extraClasses>
-							<extraClass>java.sql.Types</extraClass>
-						</extraClasses>
-					</javah>
 
 					<!-- Compiles the C sources to object files. -->
 					<c>
@@ -444,7 +496,7 @@ if ( null !== jvmdflt )
 							<includePath>${PGSQL_INCLUDEDIR}</includePath>
 							<includePath>${PGSQL_INCLUDEDIR-SERVER}</includePath>
 							<includePath>${basedir}/src/main/include/</includePath>
-							<includePath>${basedir}/target/nar/javah-include/</includePath>
+							<includePath>${javah.include}</includePath>
 						</includePaths>
 						<debug>${so.debug}</debug>
 						<optimize>${so.optimize}</optimize>
diff --git a/pljava-so/src/main/include/fallback/jdbc/java_sql_Types.h b/pljava-so/src/main/include/fallback/jdbc/java_sql_Types.h
new file mode 100644
index 000000000..2788899dc
--- /dev/null
+++ b/pljava-so/src/main/include/fallback/jdbc/java_sql_Types.h
@@ -0,0 +1,101 @@
+/*
+ * FALLBACK COPY of machine-generated file from Java 8.
+ * This file can be generated from the java.sql.Types class using the javah
+ * utility present in JDK versions through 9. Java 10 eliminates the javah
+ * utility, in favor of the -h option to javac, leaving no way to h a class,
+ * like java.sql.Types, for which the source is not present. Hence, when
+ * building on Java 10 or later, this fallback file will be used. As of Java 12,
+ * there have been no changes to these constants since Java 8, and this file is
+ * only needed by one PL/Java source file (type/Oid.c) that will probably go
+ * away soon. Therefore, no more elaborate workaround seems necessary.
+ */
+#include <jni.h>
+/* Header for class java_sql_Types */
+
+#ifndef _Included_java_sql_Types
+#define _Included_java_sql_Types
+#ifdef __cplusplus
+extern "C" {
+#endif
+#undef java_sql_Types_BIT
+#define java_sql_Types_BIT -7L
+#undef java_sql_Types_TINYINT
+#define java_sql_Types_TINYINT -6L
+#undef java_sql_Types_SMALLINT
+#define java_sql_Types_SMALLINT 5L
+#undef java_sql_Types_INTEGER
+#define java_sql_Types_INTEGER 4L
+#undef java_sql_Types_BIGINT
+#define java_sql_Types_BIGINT -5L
+#undef java_sql_Types_FLOAT
+#define java_sql_Types_FLOAT 6L
+#undef java_sql_Types_REAL
+#define java_sql_Types_REAL 7L
+#undef java_sql_Types_DOUBLE
+#define java_sql_Types_DOUBLE 8L
+#undef java_sql_Types_NUMERIC
+#define java_sql_Types_NUMERIC 2L
+#undef java_sql_Types_DECIMAL
+#define java_sql_Types_DECIMAL 3L
+#undef java_sql_Types_CHAR
+#define java_sql_Types_CHAR 1L
+#undef java_sql_Types_VARCHAR
+#define java_sql_Types_VARCHAR 12L
+#undef java_sql_Types_LONGVARCHAR
+#define java_sql_Types_LONGVARCHAR -1L
+#undef java_sql_Types_DATE
+#define java_sql_Types_DATE 91L
+#undef java_sql_Types_TIME
+#define java_sql_Types_TIME 92L
+#undef java_sql_Types_TIMESTAMP
+#define java_sql_Types_TIMESTAMP 93L
+#undef java_sql_Types_BINARY
+#define java_sql_Types_BINARY -2L
+#undef java_sql_Types_VARBINARY
+#define java_sql_Types_VARBINARY -3L
+#undef java_sql_Types_LONGVARBINARY
+#define java_sql_Types_LONGVARBINARY -4L
+#undef java_sql_Types_NULL
+#define java_sql_Types_NULL 0L
+#undef java_sql_Types_OTHER
+#define java_sql_Types_OTHER 1111L
+#undef java_sql_Types_JAVA_OBJECT
+#define java_sql_Types_JAVA_OBJECT 2000L
+#undef java_sql_Types_DISTINCT
+#define java_sql_Types_DISTINCT 2001L
+#undef java_sql_Types_STRUCT
+#define java_sql_Types_STRUCT 2002L
+#undef java_sql_Types_ARRAY
+#define java_sql_Types_ARRAY 2003L
+#undef java_sql_Types_BLOB
+#define java_sql_Types_BLOB 2004L
+#undef java_sql_Types_CLOB
+#define java_sql_Types_CLOB 2005L
+#undef java_sql_Types_REF
+#define java_sql_Types_REF 2006L
+#undef java_sql_Types_DATALINK
+#define java_sql_Types_DATALINK 70L
+#undef java_sql_Types_BOOLEAN
+#define java_sql_Types_BOOLEAN 16L
+#undef java_sql_Types_ROWID
+#define java_sql_Types_ROWID -8L
+#undef java_sql_Types_NCHAR
+#define java_sql_Types_NCHAR -15L
+#undef java_sql_Types_NVARCHAR
+#define java_sql_Types_NVARCHAR -9L
+#undef java_sql_Types_LONGNVARCHAR
+#define java_sql_Types_LONGNVARCHAR -16L
+#undef java_sql_Types_NCLOB
+#define java_sql_Types_NCLOB 2011L
+#undef java_sql_Types_SQLXML
+#define java_sql_Types_SQLXML 2009L
+#undef java_sql_Types_REF_CURSOR
+#define java_sql_Types_REF_CURSOR 2012L
+#undef java_sql_Types_TIME_WITH_TIMEZONE
+#define java_sql_Types_TIME_WITH_TIMEZONE 2013L
+#undef java_sql_Types_TIMESTAMP_WITH_TIMEZONE
+#define java_sql_Types_TIMESTAMP_WITH_TIMEZONE 2014L
+#ifdef __cplusplus
+}
+#endif
+#endif
diff --git a/pljava/pom.xml b/pljava/pom.xml
index 1dc458c73..aec2eef16 100644
--- a/pljava/pom.xml
+++ b/pljava/pom.xml
@@ -16,6 +16,29 @@
 			<version>${project.version}</version>
 		</dependency>
 	</dependencies>
+
+	<profiles>
+		<profile>
+			<id>usejavac-h</id>
+			<activation>
+				<jdk>[10,)</jdk>
+			</activation>
+			<build>
+				<plugins>
+					<plugin>
+						<groupId>org.apache.maven.plugins</groupId>
+						<artifactId>maven-compiler-plugin</artifactId>
+						<configuration>
+							<compilerArguments>
+								<h>${basedir}/target/javah-include</h>
+							</compilerArguments>
+						</configuration>
+					</plugin>
+				</plugins>
+			</build>
+		</profile>
+	</profiles>
+
 	<build>
 		<plugins>
 			<plugin>
diff --git a/pom.xml b/pom.xml
index 789c1a76d..69bcc36f4 100644
--- a/pom.xml
+++ b/pom.xml
@@ -66,6 +66,45 @@
 		</site>
 	</distributionManagement>
 
+	<profiles>
+		<profile>
+			<id>srctgt6</id>
+			<activation>
+				<jdk>[1.6,12)</jdk>
+			</activation>
+			<build>
+				<plugins>
+					<plugin>
+						<groupId>org.apache.maven.plugins</groupId>
+						<artifactId>maven-compiler-plugin</artifactId>
+						<configuration>
+							<source>1.6</source>
+							<target>1.6</target>
+						</configuration>
+					</plugin>
+				</plugins>
+			</build>
+		</profile>
+		<profile>
+			<id>srctgt7</id>
+			<activation>
+				<jdk>[12,)</jdk>
+			</activation>
+			<build>
+				<plugins>
+					<plugin>
+						<groupId>org.apache.maven.plugins</groupId>
+						<artifactId>maven-compiler-plugin</artifactId>
+						<configuration>
+							<source>7</source>
+							<target>7</target>
+						</configuration>
+					</plugin>
+				</plugins>
+			</build>
+		</profile>
+	</profiles>
+
 	<build>
 		<pluginManagement>
 			<plugins>
@@ -87,12 +126,7 @@
 				<artifactId>maven-compiler-plugin</artifactId>
 				<version>2.5.1</version>
 				<configuration>
-					<source>1.6</source>
-					<target>1.6</target>
 					<encoding>${project.build.sourceEncoding}</encoding>
-					<compilerArguments>
-						<bootclasspath>${env.JAVA_HOME}/jre/lib/rt.jar</bootclasspath>
-					</compilerArguments>
 				</configuration>
 			</plugin>
 			<plugin>
diff --git a/src/site/markdown/build/build.md b/src/site/markdown/build/build.md
index 26333ed3b..17a23b711 100644
--- a/src/site/markdown/build/build.md
+++ b/src/site/markdown/build/build.md
@@ -12,6 +12,7 @@ To do that, continue with the [installation instructions][inst].
 [orjava]: http://www.oracle.com/technetwork/java/javase/downloads/index.html
 [OpenJDK]: https://adoptopenjdk.net/
 [hsj9]: https://www.eclipse.org/openj9/oj9_faq.html
+[GraalVM]: https://www.graalvm.org/downloads/
 
 **In case of build difficulties:**
 
@@ -33,14 +34,12 @@ There is a "troubleshooting the build" section at the end of this page.
 
         javac  -version
 
-    just works. [Oracle Java][orjava] or [OpenJDK][] can be used, the latter
-    with [either the Hotspot or the OpenJ9 JVM][hsj9]. It is not necessary to
-    use the same JDK to build PL/Java that will later be used to run it in the
-    database, as long as the one used for building is not newer than that used
-    at run time. In particular, because the build procedure has not been updated
-    for Java 9 and later, PL/Java requires a Java 8, 7, or 6 JDK to build, but
-    can then use a later Java version at run time, and support PL/Java
-    applications using the newer Java features.
+    just works. PL/Java can be built with [Oracle Java][orjava] or [OpenJDK][],
+    the latter with [either the Hotspot or the OpenJ9 JVM][hsj9], or with
+    [GraalVM][]. It is not necessary to use the same JDK to build PL/Java that
+    will later be used to run it in the database, and PL/Java applications can
+    generally take advantage of recent features in whatever Java version is
+    used at run time. (See more on [version compatibility](versions.html).)
 
 0. The PostgreSQL server version that you intend to use should be installed,
     and on your search path so that the command
diff --git a/src/site/markdown/build/versions.md b/src/site/markdown/build/versions.md
index 475f6d848..77e6a1e4c 100644
--- a/src/site/markdown/build/versions.md
+++ b/src/site/markdown/build/versions.md
@@ -1,6 +1,6 @@
 # Versions of external packages needed to build and use PL/Java
 
-As of October 2018, the following version constraints are known.
+As of June 2019, the following version constraints are known.
 
 ## Java
 
@@ -14,10 +14,12 @@ implemented. Since Java 8, even JDBC additions have not caused problems for
 existing PL/Java code, as they have taken advantage of the default-methods
 feature introduced in that release.
 
-In the PL/Java 1.5.x series, the build system has not been reworked for
-building with Java 9 or newer. However, PL/Java can be built with Java 8
-and use a newer JVM at run time, simply by setting
-[the `pljava.libjvm_location` variable][jvml] to the newer version's library.
+In the PL/Java 1.5.x series, the build can be done with Java 6 or newer (but
+builds with 6 or 7
+[may be difficult](#Maven_failures_when_downloading_dependencies)).
+Once built, PL/Java is able to use another Java 6 or later JVM at run time,
+simply by setting
+[the `pljava.libjvm_location` variable][jvml] to the desired version's library.
 
 That allows PL/Java to run application code written for the latest Java
 versions, and also to take advantage of recent Java implementation advances
@@ -25,7 +27,13 @@ such as [class data sharing][cds].
 
 PL/Java has been successfully used with [Oracle Java][orj] and with
 [OpenJDK][], which is available with
-[either the Hotspot or the OpenJ9 JVM][hsj9].
+[either the Hotspot or the OpenJ9 JVM][hsj9]. It can also be built and used
+with [GraalVM][].
+
+As of Java 12, the Java compiler can no longer generate code targeting a Java 6
+runtime. If PL/Java is built with Java 12 or newer, it will not run with a JRE
+older than 7. If it is necessary to build a PL/Java that will run on 6, it must
+be built with 11 or earlier.
 
 ### Maven failures when downloading dependencies
 
@@ -41,6 +49,7 @@ newer protocol versions needed to reach the servers.
 [orj]: https://www.oracle.com/technetwork/java/javase/downloads/index.html
 [OpenJDK]: https://adoptopenjdk.net/
 [hsj9]: https://www.eclipse.org/openj9/oj9_faq.html
+[GraalVM]: https://www.graalvm.org/
 
 ## Maven