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Fix deadlock issue in #50 #61

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Fix deadlock issue in #50 #61

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78 changes: 37 additions & 41 deletions JCL2/core/src/main/java/org/xeustechnologies/jcl/AbstractClassLoader.java
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,8 @@
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import edu.emory.mathcs.backport.java.util.concurrent.ConcurrentSkipListSet;

/**
* Abstract class loader that can load classes from different resources
*
Expand All @@ -37,13 +39,21 @@
@SuppressWarnings("unchecked")
public abstract class AbstractClassLoader extends ClassLoader {

// we could use concurrent sorted set like ConcurrentSkipListSet here instead, which would be automatically sorted
// We could use concurrent sorted set like ConcurrentSkipListSet here instead, which would be automatically sorted
// and wouldn't require the lock.
// But that was added in 1.6, and according to Maven we're targeting 1.5+.
/**
* Note that all iterations over this list *must* synchronize on it first!
*/
protected final List<ProxyClassLoader> loaders = Collections.synchronizedList(new ArrayList<ProxyClassLoader>());
// protected final List<ProxyClassLoader> loaders = Collections.synchronizedList(new ArrayList<ProxyClassLoader>());

// Now we use concurrent sorted set to just resolve the deadlock issue
// https://github.com/kamranzafar/JCL/issues/50
// protected final List<ProxyClassLoader> loaders = new SetList<ProxyClassLoader>(new ConcurrentSkipListSet<ProxyClassLoader>());
/**
* Omit type argument since it's not needed in backport implementation
*/
protected final List<ProxyClassLoader> loaders = new SetList<ProxyClassLoader>(new ConcurrentSkipListSet());

private final ProxyClassLoader systemLoader = new SystemLoader();
private final ProxyClassLoader parentLoader = new ParentLoader();
Expand All @@ -70,20 +80,14 @@ public AbstractClassLoader() {
}

protected void addDefaultLoader() {
synchronized (loaders) {
loaders.add(systemLoader);
loaders.add(parentLoader);
loaders.add(currentLoader);
loaders.add(threadLoader);
Collections.sort(loaders);
}
loaders.add(systemLoader);
loaders.add(parentLoader);
loaders.add(currentLoader);
loaders.add(threadLoader);
}

public void addLoader(ProxyClassLoader loader) {
synchronized (loaders) {
loaders.add(loader);
Collections.sort(loaders);
}
loaders.add(loader);
}

/*
Expand Down Expand Up @@ -116,13 +120,11 @@ public Class loadClass(String className, boolean resolveIt) throws ClassNotFound
}

if (clazz == null) {
synchronized (loaders) {
for (ProxyClassLoader l : loaders) {
if (l.isEnabled()) {
clazz = l.loadClass(className, resolveIt);
if (clazz != null)
break;
}
for (ProxyClassLoader l : loaders) {
if (l.isEnabled()) {
clazz = l.loadClass(className, resolveIt);
if (clazz != null)
break;
}
}
}
Expand Down Expand Up @@ -153,13 +155,11 @@ public URL getResource(String name) {
}

if (url == null) {
synchronized (loaders) {
for (ProxyClassLoader l : loaders) {
if (l.isEnabled()) {
url = l.findResource(name);
if (url != null)
break;
}
for (ProxyClassLoader l : loaders) {
if (l.isEnabled()) {
url = l.findResource(name);
if (url != null)
break;
}
}
}
Expand Down Expand Up @@ -187,13 +187,11 @@ public Enumeration<URL> getResources(String name) throws IOException {
}

if (url == null) {
synchronized (loaders) {
for (ProxyClassLoader l : loaders) {
if (l.isEnabled()) {
url = l.findResource(name);
if (url != null) {
urlVector.add(url);
}
for (ProxyClassLoader l : loaders) {
if (l.isEnabled()) {
url = l.findResource(name);
if (url != null) {
urlVector.add(url);
}
}
}
Expand Down Expand Up @@ -222,13 +220,11 @@ public InputStream getResourceAsStream(String name) {
}

if (is == null) {
synchronized (loaders) {
for (ProxyClassLoader l : loaders) {
if (l.isEnabled()) {
is = l.loadResource(name);
if (is != null)
break;
}
for (ProxyClassLoader l : loaders) {
if (l.isEnabled()) {
is = l.loadResource(name);
if (is != null)
break;
}
}
}
Expand Down
8 changes: 6 additions & 2 deletions JCL2/core/src/main/java/org/xeustechnologies/jcl/JarClassLoader.java
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,8 @@
import org.xeustechnologies.jcl.exception.JclException;
import org.xeustechnologies.jcl.exception.ResourceNotFoundException;

import edu.emory.mathcs.backport.java.util.concurrent.ConcurrentHashMap;

/**
* Reads the class bytes from jar files and other resources using
* ClasspathResources
Expand All @@ -53,14 +55,16 @@ public class JarClassLoader extends AbstractClassLoader {

public JarClassLoader() {
classpathResources = new ClasspathResources();
classes = Collections.synchronizedMap( new HashMap<String, Class>() );
// classes = Collections.synchronizedMap( new HashMap<String, Class>() );
classes = new ConcurrentHashMap();
initialize();
}

public JarClassLoader(final ClassLoader parent) {
super(parent);
classpathResources = new ClasspathResources();
classes = Collections.synchronizedMap( new HashMap<String, Class>() );
// classes = Collections.synchronizedMap( new HashMap<String, Class>() );
classes = new ConcurrentHashMap();
initialize();
}

Expand Down
57 changes: 57 additions & 0 deletions JCL2/core/src/main/java/org/xeustechnologies/jcl/SetList.java
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Original file line number Diff line number Diff line change
@@ -0,0 +1,57 @@
package org.xeustechnologies.jcl;

import java.util.*;
import java.io.Serializable;

import edu.emory.mathcs.backport.java.util.concurrent.ConcurrentSkipListSet;

public class SetList<E>
extends AbstractList<E>
implements List<E>, RandomAccess, Cloneable, Serializable {
protected final Set<E> underlying;
public SetList() {
// underlying = new ConcurrentSkipListSet<E>();
underlying = new ConcurrentSkipListSet();
}
public SetList(Set<E> other) {
underlying = other;
}
public E get(int index) {
Iterator<E> it = iterator();
for (int i = 0; i < index; i++) {
if (it.hasNext()) {
it.next();
} else {
throw new IndexOutOfBoundsException();
}
}
return it.next();
}
public int size() {
return underlying.size();
}
public E set(int index, E elem) {
if (add(elem)) {
return elem;
} else {
return null;
}
}
public boolean add(E elem) {
return underlying.add(elem);
}
public void add(int index, E elem) {
add(elem);
}
public E remove(int index) {
E elem = get(index);
if (underlying.remove(elem)) {
return elem;
} else {
return null;
}
}
public Iterator<E> iterator() {
return underlying.iterator();
}
}
6 changes: 6 additions & 0 deletions JCL2/core/src/main/java/org/xeustechnologies/jcl/context/JclContext.java
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,8 @@
import org.xeustechnologies.jcl.JarClassLoader;
import org.xeustechnologies.jcl.exception.JclContextException;

import edu.emory.mathcs.backport.java.util.concurrent.ConcurrentHashMap;

/**
* JclContext holds all the JarClassLoader instances so that they can be
* accessed from anywhere in the application.
Expand All @@ -32,8 +34,12 @@
*
*/
public class JclContext {
/*
private static final Map<String, JarClassLoader> loaders = Collections
.synchronizedMap( new HashMap<String, JarClassLoader>() );
private static final Map<String, JarClassLoader> loaders = new ConcurrentHashMap<String, JarClassLoader>();
*/
private static final Map<String, JarClassLoader> loaders = new ConcurrentHashMap();
public static final String DEFAULT_NAME = "jcl";

public JclContext() {
Expand Down
5 changes: 5 additions & 0 deletions JCL2/pom.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -147,6 +147,11 @@
<artifactId>object-cloner</artifactId>
<version>0.1</version>
</dependency>
<dependency>
<groupId>backport-util-concurrent</groupId>
<artifactId>backport-util-concurrent</artifactId>
<version>3.1</version>
</dependency>
</dependencies>

<profiles>
Expand Down