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

SEVERE: The web application [/techrevmanager5] created a ThreadLocal with key of type [com.opensymphony.xwork2.inject.ContainerImpl$3] (value [com.opensymphony.xwork2.inject.ContainerImpl$3@49860b6d]) 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.

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：

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。
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]);
}
}