如何使用 servlet 运行长时间运行的进程

Question

我有一种情况，我需要启动一个运行 4 小时的任务。我正在使用 servlet 来启动该过程。但是我遇到了内存泄漏异常。

Aug 10, 2016 2:08:05 PM org.apache.catalina.core.StandardContext reload
INFO: Reloading Context with name [/] has started
Aug 10, 2016 2:08:05 PM org.apache.catalina.core.StandardWrapper unload
INFO: Waiting for 1 instance(s) to be deallocated for Servlet [Servlet]
Aug 10, 2016 2:08:06 PM org.apache.catalina.core.StandardWrapper unload
INFO: Waiting for 1 instance(s) to be deallocated for Servlet [Servlet]
Aug 10, 2016 2:08:07 PM org.apache.catalina.core.StandardWrapper unload
INFO: Waiting for 1 instance(s) to be deallocated for Servlet [DayZeroServlet]
Aug 10, 2016 2:08:07 PM org.apache.catalina.loader.WebappClassLoaderBase clearReferencesThreads
WARNING: The web application [xxx#Day0MS] is still processing a request that has yet to finish. This is very likely to create a memory leak. You can control the time allowed for requests to finish by using the unloadDelay attribute of the standard Context implementation. Stack trace of request processing thread:
java.net.SocketOutputStream.socketWrite0(Native Method)
java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:109)

下面是代码，我正在使用

protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
    PrintWriter out = response.getWriter();
    if (!GehDAO.getProcessFlag()) {
        GehDAO.updateProcessFlag(true);
        out.println("Transformation started  ...");
        closeWriter(out);
        execute();  // This step start the long running process
    }
    else {
        out.println("Transformation Already Running  ...");
        closeWriter(out);
    }
}

有没有办法在单独的进程中运行 execute() 方法？

我想在一个月内运行一次或两次这个 servlet，以启动长时间运行的进程。

Answer 1

您不能将execute() 调用封装到一个线程中吗？

new Thread(() -> execute()).start();

或者对于较早的 Java8 之前的版本：

new Thread(new Runnable() {
    public void run() { execute(); }
}).start();

附注：确保您管理关机。您通常可以使用ServletContextListener 执行此操作。基本上，如果上下文被破坏，请在长时间运行的线程上设置一个布尔标志，让它知道它需要停止，因为应用服务器正在等待它完成以关闭。