Starting a threadpool in a servlet container

Question

I have a servlet S which handles callbacks from a 3rd party site.

The callback invocations happen in a specific order. Thus, I need to queue them.

I propos

Answer 1

Using Listeners I created a ThreadPool that I can integrate with a legacy Tomcat app using the ServletContext to store the ThreadPool and let the listener manage the life cycle so it won't linger.

@WebListener
public class MyThreadPool implements ServletContextListener {

    private static final String CONTEXT_ATTRIBUTE = "MyThreadPool";
    private ExecutorService myThreadPool;

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        myThreadPool = Executors.newFixedThreadPool(10);
        sce.getServletContext().setAttribute(CONTEXT_ATTRIBUTE, myThreadPool);
    }

    public static ExecutorService getPool(Servlet servlet) {
        return (ExecutorService) servlet.getServletConfig()
               .getServletContext().getAttribute(CONTEXT_ATTRIBUTE);
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        myThreadPool.shutdown();
        sce.getServletContext().removeAttribute(CONTEXT_ATTRIBUTE);
    }
}