Getting information through Servlet from running Java Thread

Question

I have a little problem figuring this out the right way.

I have a Java application reading a log file continuously using threads. While that application is still reading the log file, a client should be able to query the current status (i.e. a certain key was found in the log file) through a java servlet.

My current issue is that I am having problems getting that status using the doGet-Method of the servlet. WHile running the thread is supposed to change a single boolean variable.

My question is:

How do I get the Log Reader Thread to start running when I deploy the Servlet on my Tomcat. In idle mode the Log Reader is listening for new files in a folder and starts to read them once they appear?

sunleo · Accepted Answer · 2012-11-08T08:41:42.863

1

Please check below link you can use SevletcontexListener

In SevletcontexListener you can start you logger

Link

public void contextInitialized(ServletContextEvent servletContextEvent) 
    {
          System.out.println("ServletContextListener started"); 
         //start thread here
    }
public void contextDestroyed(ServletContextEvent servletContextEvent) {
     //stop thread here
}

edited Nov 08 '12 at 08:41

answered Nov 08 '12 at 07:23

sunleo

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Okay. So I have that ContextListener running. How does the listener run my thread though? Thanks for your help! – mgrstnr Nov 08 '12 at 07:43
include your Thread work in a separate class and instantiate that class in Listener. – sunleo Nov 08 '12 at 07:59
you probably also want to shutdown the thread on `contextDestroyed`, otherwise the web server cannot undeploy or shutdown cleanly. – Thilo Nov 08 '12 at 08:06
Okay this starts my Thread with the web service. Now I have the problem that my Tomcat does not startup as it is waiting for the thread to finish. What do I do here? – mgrstnr Nov 08 '12 at 10:15

score 1 · Answer 2 · edited May 23 '17 at 12:20

My current issue is that I am having problems getting that status using the doGet-Method of the servlet. WHile running the thread is supposed to change a single boolean variable.

That's probably because of concurrent update of non thread-safe boolean value. For more details on this topic you can read following tutorial on Java Concurrency

How do I get the Log Reader Thread to start running when I deploy the Servlet on my Tomcat. In idle mode the Log Reader is listening for new files in a folder and starts to read them once they appear?

Please refer to following answer, where it is described how to start threads from ServletContextListener using Executors, which are high-level abstractions over threads.

Hope this helps...

Getting information through Servlet from running Java Thread

2 Answers2