[FIXED] Tomcat background processing

Issue

I am using Tomcat 9.0 to run Java code on some data from a database. I have a single servlet that is invoked by directly accessing x.x.x.x:8080/myapp/myservlet. The length of time to complete is between 5 seconds - 1 minute.

The servlet returns a response right away, leaving it to continue processing in the background. I am not sure Tomcat is supposed to be used like this. The problem is until the processing has actually finished, the web client cannot access x.x.x.x:8080/myapp/myservlet.

Each new web client can connect and invoke the servlet fine.

I simply want to invoke my java code as a background process in a fire and forget manner. Is this possible with Tomcat?

Any guidance would be great

Solution

Move you code in a Thread or an executor and use the servlet only to start and monitor the execution.

public class myservlet extends HttpServlet
{
...
Thread t = null;

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
     throws ServletException, IOException
{
    response.setContentType("text/plain;charset=UTF-8");
    PrintWriter out = response.getWriter();

    if(t == null || !t.isAlive())
    {
        t = new Thread(new Runner());
        t.setDaemon(true);
        t.start();
        out.write("Process started.\n");
    }
    else
        out.write("Process running...\n");
}

public static class Runner implements Runnable
{
  public void run()
  {
    // put your code here
  }
}
}

Answered By - Nicola De Nisco
Answer Checked By - Pedro (JavaFixing Volunteer)