Java – how to prevent memory leaks

I use quartz in my project My web application apparently caused a memory leak when it stopped. The error is:

SEVERE: A web application appears to have started a TimerThread named [Timer-12] via the java.util.Timer API but has Failed to stop it. To prevent a memory leak,the timer (and hence the associated thread) has been forcibly cancelled. 
Jan 2,2013 6:55:35 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: A web application appears to have started a thread named [DefaultQuartzScheduler_Worker-1] but has Failed to stop it. This is very likely to create a memory leak.

I used org quartz. ee. servlet. Quartzinitializerservlet and org quartz. ee. servlet. QuartzInitializerListener. The code of our factory is:

StdSchedulerFactory factory = (StdSchedulerFactory) context.getAttribute(QuartzInitializerListener.QUARTZ_FACTORY_KEY );

And web The settings in XML are:

<servlet>
         <servlet-name>
             QuartzInitializer
         </servlet-name>
         <display-name>
             Quartz Initializer Servlet
         </display-name>
         <servlet-class>
             org.quartz.ee.servlet.QuartzInitializerServlet
         </servlet-class>
         <load-on-startup>
             1
         </load-on-startup>
         <init-param>
             <param-name>shutdown-on-unload</param-name>
             <param-value>true</param-value>
         </init-param>
         <init-param>
             <param-name>wait-on-shutdown</param-name>
             <param-value>true</param-value>
         </init-param>
         <init-param>
             <param-name>start-scheduler-on-load</param-name>
             <param-value>true</param-value>
         </init-param>
     </servlet>
     <context-param>
         <param-name>quartz:shutdown-on-unload</param-name>
         <param-value>true</param-value>
     </context-param>
     <context-param>
         <param-name>quartz:wait-on-shutdown</param-name>
         <param-value>true</param-value>
     </context-param>
     <context-param>
         <param-name>quartz:start-on-load</param-name>
         <param-value>true</param-value>
     </context-param>
     <listener>
         <listener-class>
             org.quartz.ee.servlet.QuartzInitializerListener
         </listener-class>
     </listener>

Please help me solve this memory leak!

Solution

By implementing org quartz. Interruptible job, you can correctly interrupt the thread triggered by servlet unloading

@DisallowConcurrentExecution
public class Job implements InterruptableJob {

    private Thread thread;

    @Override
    public void execute(JobExecutionContext context) throws JobExecutionException {
        thread = Thread.currentThread();
        // ... do work
    }

    @Override
    public void interrupt() throws UnableToInterruptJobException {
        thread.interrupt();
        try {
            thread.join();
        } catch (InterruptedException e) {
            throw new UnableToInterruptJobException(e);
        } finally {
            // ... do cleanup
        }
    }
}

This example may cause race errors in thread variables if the job has not been executed before the interrupt According to the life cycle of the target application, I open the final solution If you need to execute concurrently through the same job instance, please add a solution to handle multiple threads and delete the @ disallowcurrentexecution annotation

To make this work, quartz properties org quartz. scheduler. Interruptjobsonshutdown withwait must be set to true This can be done by defining a properties file for the scheduler or by using the bean reference of the spring framework

Example quartz Properties file:

org.quartz.scheduler.interruptJobsOnShutdownWithWait=true

Note that if the scheduler is configured to wait for shutdown, only interrupts are scheduled, calling scheduler shutdown(true).