How to let the servlet container (Tomcat) interrupts/destroys a servlet request?

Question

Dear All,,,

I am new in Servlet, I used the following code to read some inputStream,

class MyServlet implements Servlet{
  void service(ServletRequest req, ServletResponse res){
  InputStream inA, inB, inC;
   //...
   inA.read(); // May block
   inB.read(); // May block
   inC.read(); // May block
   // ...
   }
 }

How to let the servlet container (Tomcat) interrupts/destroys MyServlet after some configurable time. And in this case which method(s) will it call?

thanks in advance,,,

Answer 1

You don't call those methods, the container does.

I'd wonder why you would do this. Do you really want to re-read those files with every request? If you need the contents, I'd prefer to see you read them in the init method and cache them.

Answer 2

I don't believe you can do that using Tomcat (or another servlet engine).

The simplest way may be to spawn off the time-consuming process in a separate thread, invoke that and time out on that invocation. You can do that easily by using a FutureTask object and calling get() on it, specifying a timeout. You'll get a TimeoutException if the task takes too long, and you can use the servlet to report this (nicely) to the user.

e.g. (very simple)

FutureTask f = new FutureTask(new Runnable{...});
try {
   Object o = f.get(TIMEOUT, UNITS)
   // report success
}
catch (TimeoutException e) {
   // report failure
}

Answer 3

This is perhaps the best approximation without using your own threads: The service method can throw javax.servlet.UnavailableException which will signal container that the servlet is not available temporarily or permanently.