在注销jdbc驱动程序后停止/中断线程 [英] stop/interrupt a thread after jdbc Driver has been deregister

问题描述

我想在注销jdbc驱动程序后通过调用方法来关闭线程.

I want to close a thread by calling a method after the jdbc Driver has been deregister.

public class CleanupContextListener implements ServletContextListener{
    boolean driverDeregisterFlag = false;

        public void contextInitialized(ServletContextEvent servletContextEvent) {
            //To change body of implemented methods use File | Settings | File Templates.
        }

        public void contextDestroyed(ServletContextEvent servletContextEvent) {
            Enumeration<Driver> drivers = DriverManager.getDrivers();
            while(drivers.hasMoreElements()) {
                Driver driver = drivers.nextElement();
                ClassLoader driverClassLoader = driver.getClass().getClassLoader();
                ClassLoader thisClassLoader = this.getClass().getClassLoader();
                if (driverClassLoader != null && thisClassLoader != null && driverClassLoader.equals(thisClassLoader)) {
                   try {
                       DriverManager.deregisterDriver(driver);
                       driverDeregisterFlag = true;
                   } catch (SQLException e) {
                       e.printStackTrace();
                   }
                }
            }
            if (driverDeregisterFlag) {
                ConfigManager.stopCurrentThread();    
            }
        }
    }

如您所见，我正在尝试调用ConfigManager.stopCurrentThread()并停止当前线程. ConfigManager是实现Runnable的类. stopCurrentThread()在ConfigManager中定义为空方法.
我想在stopCurrentThread()中放入一些代码，然后关闭ConfigManager中的线程.

As you can see I'm trying to call the ConfigManager.stopCurrentThread() and stop the current Thread. ConfigManager is a class that implements Runnable. stopCurrentThread(), is defined as an empty method in ConfigManager.
I want to put some code inside stopCurrentThread() and close the thread from ConfigManager.

我该怎么做?

推荐答案

这是我的代码的片段，它正在解决类似的问题.在c3p0 pool + tomcat 8上进行了测试，但是您可能可以根据需要对其进行修改.

This is fragment of my code which is solving similar problem. Tested on c3p0 pool + tomcat 8, but you will be probably able to modify it to you needs.

/**
 * Destroying application context. We need to safely stop exporting thread
 * and do cleanup.
 * 
 * @param arg0
 *            reason for cleanup
 */
@Override
public void contextDestroyed(@NotNull ServletContextEvent arg0) {

    // Safely stop exporting service and shut down the application context
    super.contextDestroyed(arg0);

    // Close all JDBC connections
    C3P0Registry.getNumPooledDataSources();
    Iterator<?> it = C3P0Registry.getPooledDataSources().iterator();
    while (it.hasNext()) {
        try {
            PooledDataSource dataSource = (PooledDataSource) it.next();
            dataSource.close();
        } catch (Exception e) {
            log.error("Error when closing connections ...", e);
        }
    }

    // This manually unregisters JDBC drivers, which prevents Tomcat 7 from
    // complaining about memory leaks with this class
    Enumeration<Driver> drivers = DriverManager.getDrivers();
    while (drivers.hasMoreElements()) {
        Driver driver = drivers.nextElement();
        try {
            DriverManager.deregisterDriver(driver);
            log.info(String.format("Unregistering jdbc driver: %s", driver));
        } catch (SQLException e) {
            log.error(
                    String.format("Error deregistering driver %s", driver),
                    e);
        }
    }

    // Waiting for daemon close() c3p0 jdbc pool thread
    Set<Thread> threadSet = Thread.getAllStackTraces().keySet();
    for (Thread th : threadSet) {
        if (th.isDaemon()) {
            try {
                if (th.getName().equals(
                        "Resource Destroyer in BasicResourcePool.close()")) {
                    th.join();
                }
            } catch (Exception ex) {
                log.info("Shutdown waiting was interrupted ...");
            }
        }
    }
    // Clear all thread local variables, this prevents Tomcat 7 from
    // complaining about memory leaks
    immolate();

}

/**
 * Cleanup function which cleans all thread local variables. Using thread
 * local variables is not a good practice but unfortunately some libraries
 * are still using them. We need to clean them up to prevent memory leaks.
 * 
 * @return number of Thread local variables
 */
private int immolate() {
    int count = 0;
    try {
        final Field threadLocalsField = Thread.class
                .getDeclaredField("threadLocals");
        threadLocalsField.setAccessible(true);
        final Field inheritableThreadLocalsField = Thread.class
                .getDeclaredField("inheritableThreadLocals");
        inheritableThreadLocalsField.setAccessible(true);
        for (final Thread thread : Thread.getAllStackTraces().keySet()) {
            count += clear(threadLocalsField.get(thread));
            count += clear(inheritableThreadLocalsField.get(thread));
        }
        log.info("Immolated " + count + " values in ThreadLocals");
    } catch (Exception e) {
        log.error("ThreadLocalImmolater.immolate()", e);
    }
    return count;
}

/**
 * Cleaner for thread local map.
 * 
 * @param threadLocalMap
 *            thread local map to clean or null
 * @return number of cleaned objects
 * @throws Exception
 *             in case of error
 */
private int clear(@NotNull final Object threadLocalMap) throws Exception {
    if (threadLocalMap == null) {
        return 0;
    }
    int count = 0;
    final Field tableField = threadLocalMap.getClass().getDeclaredField(
            "table");
    tableField.setAccessible(true);
    final Object table = tableField.get(threadLocalMap);
    for (int i = 0, length = Array.getLength(table); i < length; ++i) {
        final Object entry = Array.get(table, i);
        if (entry != null) {
            final Object threadLocal = ((WeakReference<?>) entry).get();
            if (threadLocal != null) {
                log(i, threadLocal);
                Array.set(table, i, null);
                ++count;
            }
        }
    }
    return count;
}

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