/*
* Copyright 2002-2010 the original author or authors.
*
* Licensed 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.
*/
package org.springframework.aop.target;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import org.springframework.aop.IntroductionAdvisor;
import org.springframework.aop.support.DefaultIntroductionAdvisor;
import org.springframework.aop.support.DelegatingIntroductionInterceptor;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.core.NamedThreadLocal;
/**
* Alternative to an object pool. This TargetSource uses a threading model in which
* every thread has its own copy of the target. There's no contention for targets.
* Target object creation is kept to a minimum on the running server.
*
* <p>Application code is written as to a normal pool; callers can't assume they
* will be dealing with the same instance in invocations in different threads.
* However, state can be relied on during the operations of a single thread:
* for example, if one caller makes repeated calls on the AOP proxy.
*
* <p>Cleanup of thread-bound objects is performed on BeanFactory destruction,
* calling their <code>DisposableBean.destroy()</code> method if available.
* Be aware that many thread-bound objects can be around until the application
* actually shuts down.
*
* @author Rod Johnson
* @author Juergen Hoeller
* @author Rob Harrop
* @see ThreadLocalTargetSourceStats
* @see org.springframework.beans.factory.DisposableBean#destroy()
*/
public class ThreadLocalTargetSource extends AbstractPrototypeBasedTargetSource
implements ThreadLocalTargetSourceStats, DisposableBean {
/**
* ThreadLocal holding the target associated with the current
* thread. Unlike most ThreadLocals, which are static, this variable
* is meant to be per thread per instance of the ThreadLocalTargetSource class.
*/
private final ThreadLocal<Object> targetInThread =
new NamedThreadLocal<Object>("Thread-local instance of bean '" + getTargetBeanName() + "'");
/**
* Set of managed targets, enabling us to keep track of the targets we've created.
*/
private final Set<Object> targetSet = Collections.synchronizedSet(new HashSet<Object>());
private int invocationCount;
private int hitCount;
/**
* Implementation of abstract getTarget() method.
* We look for a target held in a ThreadLocal. If we don't find one,
* we create one and bind it to the thread. No synchronization is required.
*/
public Object getTarget() throws BeansException {
++this.invocationCount;
Object target = this.targetInThread.get();
if (target == null) {
if (logger.isDebugEnabled()) {
logger.debug("No target for prototype '" + getTargetBeanName() + "' bound to thread: " +
"creating one and binding it to thread '" + Thread.currentThread().getName() + "'");
}
// Associate target with ThreadLocal.
target = newPrototypeInstance();
this.targetInThread.set(target);
this.targetSet.add(target);
}
else {
++this.hitCount;
}
return target;
}
/**
* Dispose of targets if necessary; clear ThreadLocal.
* @see #destroyPrototypeInstance
*/
public void destroy() {
logger.debug("Destroying ThreadLocalTargetSource bindings");
synchronized (this.targetSet) {
for (Object target : this.targetSet) {
destroyPrototypeInstance(target);
}
this.targetSet.clear();
}
// Clear ThreadLocal, just in case.
this.targetInThread.remove();
}
public int getInvocationCount() {
return this.invocationCount;
}
public int getHitCount() {
return this.hitCount;
}
public int getObjectCount() {
return this.targetSet.size();
}
/**
* Return an introduction advisor mixin that allows the AOP proxy to be
* cast to ThreadLocalInvokerStats.
*/
public IntroductionAdvisor getStatsMixin() {
DelegatingIntroductionInterceptor dii = new DelegatingIntroductionInterceptor(this);
return new DefaultIntroductionAdvisor(dii, ThreadLocalTargetSourceStats.class);
}
}