ThreadLocal 引起的内存泄露
最近在用LOADRUNNER做性能测试，
运行几个小时后，内存一直增加， 最后出现了内存OutMemory问题。
已知的一个BUG：
http://java.net/jira/browse/JAXB-844
JAXB 2.1.15 有问题类Coordinator
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can obtain
* a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
* or glassfish/bootstrap/legal/LICENSE.txt. See the License for the specific
* language governing permissions and limitations under the License.
*
* When distributing the software, include this License Header Notice in each
* file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
* Sun designates this particular file as subject to the "Classpath" exception
* as provided by Sun in the GPL Version 2 section of the License file that
* accompanied this code. If applicable, add the following below the License
* Header, with the fields enclosed by brackets [] replaced by your own
* identifying information: "Portions Copyrighted [year]
* [name of copyright owner]"
*
* Contributor(s):
*
* If you wish your version of this file to be governed by only the CDDL or
* only the GPL Version 2, indicate your decision by adding "[Contributor]
* elects to include this software in this distribution under the [CDDL or GPL
* Version 2] license." If you don't indicate a single choice of license, a
* recipient has the option to distribute your version of this file under
* either the CDDL, the GPL Version 2 or to extend the choice of license to
* its licensees as provided above. However, if you add GPL Version 2 code
* and therefore, elected the GPL Version 2 license, then the option applies
* only if the new code is made subject to such option by the copyright
* holder.
*/
package com.sun.xml.bind.v2.runtime;
import java.util.HashMap;
import javax.xml.bind.ValidationEvent;
import javax.xml.bind.ValidationEventHandler;
import javax.xml.bind.ValidationEventLocator;
import javax.xml.bind.annotation.adapters.XmlAdapter;
import javax.xml.bind.helpers.ValidationEventImpl;
import com.sun.xml.bind.v2.ClassFactory;
import com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallingContext;
import org.xml.sax.ErrorHandler;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
/**
* Object that coordinates the marshalling/unmarshalling.
*
* <p>
* This class takes care of the logic that allows code to obtain
* {@link UnmarshallingContext} and {@link XMLSerializer} instances
* during the unmarshalling/marshalling.
*
* <p>
* This is done by using a {@link ThreadLocal}. Therefore one unmarshalling/marshalling
* episode has to be done from the beginning till end by the same thread.
* (Note that the same {@link Coordinator} can be then used by a different thread
* for an entirely different episode.)
*
* This class also maintains the user-configured instances of {@link XmlAdapter}s.
*
* <p>
* This class implements {@link ErrorHandler} and propages erros to this object
* as the {@link ValidationEventHandler}, which will be implemented in a derived class.
*
* @author Kohsuke Kawaguchi
*/
public abstract class Coordinator implements ErrorHandler, ValidationEventHandler {
private final HashMap<Class<? extends XmlAdapter>,XmlAdapter> adapters =
new HashMap<Class<? extends XmlAdapter>,XmlAdapter>();
public final XmlAdapter putAdapter(Class<? extends XmlAdapter> c, XmlAdapter a) {
if(a==null)
return adapters.remove(c);
else
return adapters.put(c,a);
}
/**
* Gets the instance of the adapter.
*
* @return
* always non-null.
*/
public final <T extends XmlAdapter> T getAdapter(Class<T> key) {
T v = key.cast(adapters.get(key));
if(v==null) {
v = ClassFactory.create(key);
putAdapter(key,v);
}
return v;
}
public <T extends XmlAdapter> boolean containsAdapter(Class<T> type) {
return adapters.containsKey(type);
}
/**
* The {@link Coordinator} in charge before this {@link Coordinator}.
*/
private Coordinator old;
/**
* A 'pointer' to a {@link Coordinator} that keeps track of the currently active {@link Coordinator}.
* Having this improves the runtime performance.
*/
private Coordinator[] table;
/**
* When we set {@link #table} to null, record who did it.
* This is for trouble-shooting a possible concurrency issue reported at:
* http://forums.java.net/jive/thread.jspa?threadID=15132
*/
public Exception guyWhoSetTheTableToNull;
/**
* Associates this {@link Coordinator} with the current thread.
* Should be called at the very beginning of the episode.
*/
protected final void setThreadAffinity() {
table = activeTable.get();
assert table!=null;
}
/**
* Dis-associate this {@link Coordinator} with the current thread.
* Sohuld be called at the end of the episode to avoid memory leak.
*/
protected final void resetThreadAffinity() {
if(debugTableNPE)
guyWhoSetTheTableToNull = new Exception(); // remember that we set it to null
table = null;
}
/**
* Called whenever an execution flow enters the realm of this {@link Coordinator}.
*/
protected final void pushCoordinator() {
old = table[0];
table[0] = this;
}
/**
* Called whenever an execution flow exits the realm of this {@link Coordinator}.
*/
protected final void popCoordinator() {
assert table[0]==this;
table[0] = old;
old = null; // avoid memory leak
}
public static Coordinator _getInstance() {
return activeTable.get()[0];
}
// this much is necessary to avoid calling get and set twice when we push.
private static final ThreadLocal<Coordinator[]> activeTable = new ThreadLocal<Coordinator[]>() {
public Coordinator[] initialValue() {
return new Coordinator[1];
}
};
//
//
// ErrorHandler implementation
//
//
/**
* Gets the current location. Used for reporting the error source location.
*/
protected abstract ValidationEventLocator getLocation();
public final void error(SAXParseException exception) throws SAXException {
propagateEvent( ValidationEvent.ERROR, exception );
}
public final void warning(SAXParseException exception) throws SAXException {
propagateEvent( ValidationEvent.WARNING, exception );
}
public final void fatalError(SAXParseException exception) throws SAXException {
propagateEvent( ValidationEvent.FATAL_ERROR, exception );
}
private void propagateEvent( int severity, SAXParseException saxException )
throws SAXException {
ValidationEventImpl ve =
new ValidationEventImpl( severity, saxException.getMessage(), getLocation() );
Exception e = saxException.getException();
if( e != null ) {
ve.setLinkedException( e );
} else {
ve.setLinkedException( saxException );
}
// call the client's event handler. If it returns false, then bail-out
// and terminate the unmarshal operation.
boolean result = handleEvent( ve );
if( ! result ) {
// bail-out of the parse with a SAX exception, but convert it into
// an UnmarshalException back in in the AbstractUnmarshaller
throw saxException;
}
}
public static boolean debugTableNPE;
static {
try {
debugTableNPE = Boolean.getBoolean(Coordinator.class.getName()+".debugTableNPE");
} catch (SecurityException t) {
}
}
}
变量adapters一直没有进行REMOVE操作
JAXB（V2.2.25）修复后的代码如下：
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright (c) 1997-2011 Oracle and/or its affiliates. All rights reserved.
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can
* obtain a copy of the License at
* https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
* or packager/legal/LICENSE.txt. See the License for the specific
* language governing permissions and limitations under the License.
*
* When distributing the software, include this License Header Notice in each
* file and include the License file at packager/legal/LICENSE.txt.
*
* GPL Classpath Exception:
* Oracle designates this particular file as subject to the "Classpath"
* exception as provided by Oracle in the GPL Version 2 section of the License
* file that accompanied this code.
*
* Modifications:
* If applicable, add the following below the License Header, with the fields
* enclosed by brackets [] replaced by your own identifying information:
* "Portions Copyright [year] [name of copyright owner]"
*
* Contributor(s):
* If you wish your version of this file to be governed by only the CDDL or
* only the GPL Version 2, indicate your decision by adding "[Contributor]
* elects to include this software in this distribution under the [CDDL or GPL
* Version 2] license." If you don't indicate a single choice of license, a
* recipient has the option to distribute your version of this file under
* either the CDDL, the GPL Version 2 or to extend the choice of license to
* its licensees as provided above. However, if you add GPL Version 2 code
* and therefore, elected the GPL Version 2 license, then the option applies
* only if the new code is made subject to such option by the copyright
* holder.
*/
package com.sun.xml.bind.v2.runtime;
import java.util.HashMap;
import javax.xml.bind.ValidationEvent;
import javax.xml.bind.ValidationEventHandler;
import javax.xml.bind.ValidationEventLocator;
import javax.xml.bind.annotation.adapters.XmlAdapter;
import javax.xml.bind.helpers.ValidationEventImpl;
import com.sun.xml.bind.v2.ClassFactory;
import com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallingContext;
import org.xml.sax.ErrorHandler;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
/**
* Object that coordinates the marshalling/unmarshalling.
*
* <p>
* This class takes care of the logic that allows code to obtain
* {@link UnmarshallingContext} and {@link XMLSerializer} instances
* during the unmarshalling/marshalling.
*
* <p>
* This is done by using a {@link ThreadLocal}. Therefore one unmarshalling/marshalling
* episode has to be done from the beginning till end by the same thread.
* (Note that the same {@link Coordinator} can be then used by a different thread
* for an entirely different episode.)
*
* This class also maintains the user-configured instances of {@link XmlAdapter}s.
*
* <p>
* This class implements {@link ErrorHandler} and propages erros to this object
* as the {@link ValidationEventHandler}, which will be implemented in a derived class.
*
* @author Kohsuke Kawaguchi
*/
public abstract class Coordinator implements ErrorHandler, ValidationEventHandler {
private final HashMap<Class<? extends XmlAdapter>,XmlAdapter> adapters =
new HashMap<Class<? extends XmlAdapter>,XmlAdapter>();
public final XmlAdapter putAdapter(Class<? extends XmlAdapter> c, XmlAdapter a) {
if(a==null)
return adapters.remove(c);
else
return adapters.put(c,a);
}
/**
* Gets the instance of the adapter.
*
* @return
* always non-null.
*/
public final <T extends XmlAdapter> T getAdapter(Class<T> key) {
T v = key.cast(adapters.get(key));
if(v==null) {
v = ClassFactory.create(key);
putAdapter(key,v);
}
return v;
}
public <T extends XmlAdapter> boolean containsAdapter(Class<T> type) {
return adapters.containsKey(type);
}
/**
* The {@link Coordinator} in charge before this {@link Coordinator}.
*/
private Object old;
/**
* A 'pointer' to a {@link Coordinator} that keeps track of the currently active {@link Coordinator}.
* Having this improves the runtime performance.
*/
private Object[] table;
/**
* When we set {@link #table} to null, record who did it.
* This is for trouble-shooting a possible concurrency issue reported at:
* http://forums.java.net/jive/thread.jspa?threadID=15132
*/
public Exception guyWhoSetTheTableToNull;
/**
* Associates this {@link Coordinator} with the current thread.
* Should be called at the very beginning of the episode.
*/
protected final void setThreadAffinity() {
table = activeTable.get();
assert table!=null;
}
/**
* Dis-associate this {@link Coordinator} with the current thread.
* Sohuld be called at the end of the episode to avoid memory leak.
*/
protected final void resetThreadAffinity() {
if (activeTable != null) {
activeTable.remove();
}
if(debugTableNPE)
guyWhoSetTheTableToNull = new Exception(); // remember that we set it to null
table = null;
}
/**
* Called whenever an execution flow enters the realm of this {@link Coordinator}.
*/
protected final void pushCoordinator() {
old = table[0];
table[0] = this;
}
/**
* Called whenever an execution flow exits the realm of this {@link Coordinator}.
*/
protected final void popCoordinator() {
assert table[0]==this;
table[0] = old;
old = null; // avoid memory leak
}
public static Coordinator _getInstance() {
return (Coordinator) activeTable.get()[0];
}
// this much is necessary to avoid calling get and set twice when we push.
private static final ThreadLocal<Object[]> activeTable = new ThreadLocal<Object[]>() {
@Override
public Object[] initialValue() {
return new Object[1];
}
};
//
//
// ErrorHandler implementation
//
//
/**
* Gets the current location. Used for reporting the error source location.
*/
protected abstract ValidationEventLocator getLocation();
public final void error(SAXParseException exception) throws SAXException {
propagateEvent( ValidationEvent.ERROR, exception );
}
public final void warning(SAXParseException exception) throws SAXException {
propagateEvent( ValidationEvent.WARNING, exception );
}
public final void fatalError(SAXParseException exception) throws SAXException {
propagateEvent( ValidationEvent.FATAL_ERROR, exception );
}
private void propagateEvent( int severity, SAXParseException saxException )
throws SAXException {
ValidationEventImpl ve =
new ValidationEventImpl( severity, saxException.getMessage(), getLocation() );
Exception e = saxException.getException();
if( e != null ) {
ve.setLinkedException( e );
} else {
ve.setLinkedException( saxException );
}
// call the client's event handler. If it returns false, then bail-out
// and terminate the unmarshal operation.
boolean result = handleEvent( ve );
if( ! result ) {
// bail-out of the parse with a SAX exception, but convert it into
// an UnmarshalException back in in the AbstractUnmarshaller
throw saxException;
}
}
public static boolean debugTableNPE;
static {
try {
debugTableNPE = Boolean.getBoolean(Coordinator.class.getName()+".debugTableNPE");
} catch (SecurityException t) {
}
}
}
主要是加了下面这个代码修复了内存泄露问题
/**
* Dis-associate this {@link Coordinator} with the current thread.
* Sohuld be called at the end of the episode to avoid memory leak.
*/
protected final void resetThreadAffinity() {
if (activeTable != null) {
activeTable.remove();
}
if(debugTableNPE)
guyWhoSetTheTableToNull = new Exception(); // remember that we set it to null
table = null;
}
所以由THREADLOCAL创建的变量一定要进行REMOVE操作