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Solved PermGen memory leak in AccessClassLoader

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Solved the PermGen memory leak due to static strong references to the class loaders (and minor performance improvement avoiding call to Method.setAccessible() if unnecessary).
This commit is contained in:
Tumi 2013-12-23 02:15:32 +01:00
parent 395008a0b8
commit 904c1dcc84
1 changed files with 56 additions and 15 deletions
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71
src/com/esotericsoftware/reflectasm/AccessClassLoader.java
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@ -1,34 +1,69 @@
package com.esotericsoftware.reflectasm;
import java.lang.ref.WeakReference;
import java.lang.reflect.Method;
import java.security.ProtectionDomain;
import java.util.ArrayList;
import java.util.WeakHashMap;
class AccessClassLoader extends ClassLoader {
static private final ArrayList<AccessClassLoader> accessClassLoaders = new ArrayList();
// Weak-references to ClassLoaders, to avoid PermGen memory leaks for example
// in AppServers/WebContainters if the reflectasm framework (including this class)
// is loaded outside the deployed applications (WAR/EAR) using ReflectASM/Kryo
// (exts, user classpath, etc).
//
// The key is the parent ClassLoader and the value is the AccessClassLoader
// Both are weak-referenced in the HashTable.
static private final WeakHashMap<ClassLoader, WeakReference<AccessClassLoader>> accessClassLoaders = new WeakHashMap<ClassLoader, WeakReference<AccessClassLoader>>();
// Fast-path for classes loaded in the same ClassLoader than this Class
static private final ClassLoader selfContextParentClassLoader = getParentClassLoader(AccessClassLoader.class);
static private volatile AccessClassLoader selfContextAccessClassLoader = new AccessClassLoader(selfContextParentClassLoader);
static AccessClassLoader get (Class type) {
ClassLoader parent = type.getClassLoader();
synchronized (accessClassLoaders) {
for (int i = 0, n = accessClassLoaders.size(); i < n; i++) {
AccessClassLoader accessClassLoader = accessClassLoaders.get(i);
if (accessClassLoader.getParent() == parent) return accessClassLoader;
ClassLoader parent = getParentClassLoader(type);
// 1. fast-path:
if (selfContextParentClassLoader.equals(parent)) {
if (selfContextAccessClassLoader==null) {
// DCL with volatile semantics
synchronized (accessClassLoaders) {
if (selfContextAccessClassLoader==null)
selfContextAccessClassLoader = new AccessClassLoader(selfContextParentClassLoader);
}
}
return selfContextAccessClassLoader;
}
// 2. normal search:
synchronized (accessClassLoaders) {
WeakReference<AccessClassLoader> ref = accessClassLoaders.get(parent);
if (ref!=null) {
AccessClassLoader accessClassLoader = ref.get();
if (accessClassLoader!=null) return accessClassLoader;
else accessClassLoaders.remove(parent); // the value has been GC-reclaimed, but still not the key (defensive sanity)
}
if(parent == null) parent = ClassLoader.getSystemClassLoader();
AccessClassLoader accessClassLoader = new AccessClassLoader(parent);
accessClassLoaders.add(accessClassLoader);
accessClassLoaders.put(parent, new WeakReference<AccessClassLoader>(accessClassLoader));
return accessClassLoader;
}
}
static void remove (ClassLoader parent) {
synchronized (accessClassLoaders) {
for (int i = accessClassLoaders.size() - 1; i >= 0; i--) {
AccessClassLoader accessClassLoader = accessClassLoaders.get(i);
if (accessClassLoader.getParent() == parent) accessClassLoaders.remove(i);
public static void remove (ClassLoader parent) {
// 1. fast-path:
if (selfContextParentClassLoader.equals(parent)) {
selfContextAccessClassLoader = null;
}
else {
// 2. normal search:
synchronized (accessClassLoaders) {
accessClassLoaders.remove(parent);
}
}
}
public static int activeAccessClassLoaders() {
int sz = accessClassLoaders.size();
if (selfContextAccessClassLoader!=null) sz++;
return sz;
}
private AccessClassLoader (ClassLoader parent) {
super(parent);
@ -55,4 +90,10 @@ class AccessClassLoader extends ClassLoader {
}
return defineClass(name, bytes, 0, bytes.length, getClass().getProtectionDomain());
}
private static ClassLoader getParentClassLoader(Class type) {
ClassLoader parent = type.getClassLoader();
if (parent == null) parent = ClassLoader.getSystemClassLoader();
return parent;
}
}