在tomcat7下停止应用时报错:created a ThreadLocal with key of type

在tomcat7下停止应用时报错： created a ThreadLocal with key of type [com.opensymphony.xwork2.inject.ContainerImpl$10]

INFO: A valid shutdown command was received via the shutdown port. Stopping the Server instance.
Apr 02, 2015 10:36:52 AM org.apache.coyote.AbstractProtocol pause
INFO: Pausing ProtocolHandler ["http-bio-8080"]
Apr 02, 2015 10:36:52 AM org.apache.coyote.AbstractProtocol pause
INFO: Pausing ProtocolHandler ["ajp-bio-8009"]
Apr 02, 2015 10:36:52 AM org.apache.catalina.core.StandardService stopInternal
INFO: Stopping service Catalina
Apr 02, 2015 10:36:52 AM org.apache.catalina.core.ApplicationContext log
INFO: Closing Spring root WebApplicationContext
Apr 02, 2015 10:36:52 AM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
<span style="color:#ff0000;">SEVERE: The web application [/techrevmanager5] created a ThreadLocal with key of type [com.opensymphony.xwork2.inject.ContainerImpl$3] (value [[email protected]]) and a value of type [java.lang.Object[]] (value [[Ljava.lang.Object;@7f5846d0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.</span>
Apr 02, 2015 10:36:52 AM org.apache.coyote.AbstractProtocol stop
INFO: Stopping ProtocolHandler ["http-bio-8080"]
Apr 02, 2015 10:36:52 AM org.apache.coyote.AbstractProtocol stop
INFO: Stopping ProtocolHandler ["ajp-bio-8009"]
Apr 02, 2015 10:36:52 AM org.apache.coyote.AbstractProtocol destroy
INFO: Destroying ProtocolHandler ["http-bio-8080"]
Apr 02, 2015 10:36:52 AM org.apache.coyote.AbstractProtocol destroy
INFO: Destroying ProtocolHandler ["ajp-bio-8009"]

先说一下开发环境清单：

Tomcat-7.0.59

xwork-core-2.2.1

struts2-core-2.2.1

分析过程：

从错误情况来看，是xwork中的类com.opensymphony.xwork2.inject.ContainerImpl出现了问题。

下载xwork-core-2.2.1的源码，打开ContainerImpl文件,看到行557-583中的代码，确实存在内存未释放的问题：

//这里在线程变量中初始化了一维数组
ThreadLocal<Object[]> localContext =
  new ThreadLocal<Object[]>() {
	@Override
	protected Object[] initialValue() {
	  return new Object[1];
	}
  };

/**
* Looks up thread local context. Creates (and removes) a new context if
* necessary.
*/
<T> T callInContext(ContextualCallable<T> callable) {
	Object[] reference = localContext.get();
	if (reference[0] == null) {
	  reference[0] = new InternalContext(this);
	  try {
		return callable.call((InternalContext)reference[0]);
	  } finally {
		// Only remove the context if this call created it.
		reference[0] = null;
		//这里只将数组中的元素释放，并未将线程变量的数组对象释放
	  }
	} else {
	  // Someone else will clean up this context.
	  return callable.call((InternalContext)reference[0]);
	}
}

解决方法：

问题和原因都找到，那么解决起来就简单了，有两种方案可以选择：

1. 升级xwork的jar文件版本，根据我的检查，从xwork-core-2.3.3及以后的版本中这个问题就不存在了。相应地，你可以需要升级你的struts2-core-2.3.3以上。
2. 修改xwork-core-2.2.1中的com.opensymphony.xwork2.inject.ContainerImpl文件，编译后放入classpath路径下（以取代jar文件中的类）

<T> T callInContext(ContextualCallable<T> callable) {
	Object[] reference = localContext.get();
	if (reference[0] == null) {
	  reference[0] = new InternalContext(this);
	  try {
		return callable.call((InternalContext)reference[0]);
	  } finally {
		// Only remove the context if this call created it.
		reference[0] = null;
		//将线程变量的数组对象释放
		this.localContext.remove();
	  }
	} else {
	  // Someone else will clean up this context.
	  return callable.call((InternalContext)reference[0]);
	}
}