如何识别和删除从Java中的webapp启动的Threads/ThreadLocals？

Question

如何识别和删除从Java中的webapp启动的Threads/ThreadLocals？

And*_*dyT 27 java multithreading thread-local tomcat7

每当我停止或重新部署webapp时,我都会看到很多类似的错误,

msg=The web application [] created a ThreadLocal with key of type [] (value []) and 
a value of type [] (value []) but failed to remove it when the web application was 
stopped. Threads are going to be renewed over time to try and avoid probable memory leak

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我不是在我的应用程序中创建任何ThreadLocals,而是引用可能正在创建这些ThreadLocals的许多库.我们目前正在使用Tomcat 7.我已经遇到过其他类似的问题[在Tomcat中重新部署应用程序时内存泄漏或catalina.out中的这些警告是什么？]但是所有这些只是暗示这是Tomcat功能警告你ThreadLocals没有被删除.我没有看到删除ThreadLocals的任何答案.我也看到一些关于线程没有停止的错误,

msg=The web application [] appears to have started a thread named [] but has
failed to stop it. This is very likely to create a memory leak.

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这些在我们公司的中央记录系统中作为ERROR登录,从而增加了我们的应用程序的错误数量.当我们检查应用程序的性能时,这肯定不太好看.我尝试了这两个来源的实现[杀死此线程中的线程和示例代码],但似乎不起作用.它删除了我们的应用程序未创建的线程/ threadlocals.我需要的是只删除我们的webapp启动的线程/ threadlocals.我们有什么方法可以在ServletContextListener的contextDestroyed()方法中删除它们吗？以下是我当前的ServletContextListener类,

public class CustomServletContextListener implements ServletContextListener {

private List<String> threadsAtStartup;

@Override
public void contextInitialized(ServletContextEvent sce) {
    retrieveThreadsOnStartup();
}

@Override
public void contextDestroyed(ServletContextEvent sce) {
    // Now deregister JDBC drivers in this context's ClassLoader:
    // Get the webapp's ClassLoader
    ClassLoader cl = Thread.currentThread().getContextClassLoader();
    // Loop through all drivers
    Enumeration<Driver> drivers = DriverManager.getDrivers();
    while (drivers.hasMoreElements()) {
        Driver driver = drivers.nextElement();
        if (driver.getClass().getClassLoader() == cl) {
            // This driver was registered by the webapp's ClassLoader, so deregister it:
            try {
                System.out.println("Deregistering JDBC driver {}: " + driver);
                DriverManager.deregisterDriver(driver);
            } catch (SQLException ex) {
                System.out.println("Error deregistering JDBC driver {}: " + driver + "\nException: " + ex);
            }
        } else {
            // driver was not registered by the webapp's ClassLoader and may be in use elsewhere
            System.out.println("Not deregistering JDBC driver {} as it does not belong to this webapp's ClassLoader: " + driver);
        }
    }

    //Threads
    ThreadGroup threadGroup = Thread.currentThread().getThreadGroup();
    threadGroup = Thread.currentThread().getThreadGroup();
    Thread[] threads;
    try {
        threads = retrieveCurrentActiveThreads(threadGroup);
    } catch (NoSuchFieldException e) {
        System.out.println("Could not retrieve initial Threads list. The application may be unstable on shutting down " + e.getMessage());
        return;
    } catch (IllegalAccessException e) {
        System.out.println("Could not retrieve initial Threads list. The application may be unstable on shutting down " + e.getMessage());
        return;
    }

    int toBeKilledCount = 0;
    int totalThreadCount = 0;
    int killedTLCount = 0;
    int totalTLCount = 0;
    int killedITLCount = 0;
    int totalITLCount = 0;
    for (; totalThreadCount < threads.length; totalThreadCount++) {
        Thread thread = threads[totalThreadCount];
        if(thread != null) {
            String threadName = thread.getName();
            boolean shouldThisThreadBeKilled;

            shouldThisThreadBeKilled = isThisThreadToBeKilled(Thread.currentThread(), thread);
            if (shouldThisThreadBeKilled) {
                //ThreadLocal
                try {
                    removeThreadLocals("threadLocals", thread);
                    removeThreadLocals("inheritableThreadLocals", thread);
                } catch (Exception e) {
                    System.out.println("\tError accessing threadLocals field of '" + threadName + "': " + e.getMessage());
                }

                //Stop thread
                thread.interrupt();
                thread = null;
                toBeKilledCount++;
            }

        }
    }
}

private void retrieveThreadsOnStartup() {
    final Thread[] threads;
    final ThreadGroup threadGroup = Thread.currentThread().getThreadGroup();
    try {
        threads = retrieveCurrentActiveThreads(threadGroup);
    } catch (NoSuchFieldException e) {
        System.out.println("Could not retrieve initial Threads list. The application may be unstable on shutting down " + e);
        threadsAtStartup = new ArrayList<String>();
        return;
    } catch (IllegalAccessException e) {
        System.out.println("Could not retrieve initial Threads list. The application may be unstable on shutting down " + e);
        threadsAtStartup = new ArrayList<String>();
        return;
    }

    threadsAtStartup = new ArrayList<String>(threads.length);
    for (int i = 0; i < threads.length; i++) {
        final Thread thread;
        try {
            thread = threads[i];
            if (null != thread) {
                threadsAtStartup.add(thread.getName());
            }
        } catch (RuntimeException e) {
            System.out.println("An error occured on initial Thread statement: " + e);
        }
    }
}

private Thread[] retrieveCurrentActiveThreads(ThreadGroup threadGroup) throws NoSuchFieldException, IllegalAccessException {
    final Thread[] threads;
    final Field privateThreadsField;
    privateThreadsField = ThreadGroup.class.getDeclaredField("childrenThreads");
    privateThreadsField.setAccessible(true);

    threads = (Thread[]) privateThreadsField.get(threadGroup);
    return threads;
}

private void removeThreadLocals(String fieldName, Thread thread) {
    Field threadLocalsField = Thread.class.getDeclaredField(fieldName);
    threadLocalsField.setAccessible(true);
    Object threadLocalMap = threadLocalsField.get(thread);
    Field tableField = threadLocalMap.getClass().getDeclaredField("table");
    tableField.setAccessible(true);
    Object table = tableField.get(threadLocalMap);
    int count = 0;
    for (int i = 0, length = Array.getLength(table); i < length; ++i) {
        Object entry = Array.get(table, i);
        if (entry != null) {
            totalTLCount++;
            Object threadLocal = ((WeakReference)entry).get();
            if (threadLocal != null) {
                Array.set(table, i, null);
                killedTLCount++;
            }
        } 
    }   
}

private Boolean isThisThreadToBeKilled(Thread currentThread, Thread testThread) {
    boolean toBeKilled;
    String currentThreadName = currentThread.getName();
    String testThreadName = testThread.getName();
    System.out.println("currentThreadName: " + currentThreadName + ", testThreadName: " + testThreadName);
    return !threadsAtStartup.contains(testThreadName)               // this thread was not already running at startup
            && !testThreadName.equalsIgnoreCase(currentThreadName); // this is not the currently running thread

}

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}

更新:我仍然无法解决此问题.有帮助吗？没有人遇到过这些？