Is it safe to use java.util.Timer inside servlet ?

Question

Hi all,

for many reasons, it is not good practice to use threads inside servlet. java.util.Timer seems like wrapper to threads. so also it is not safe to use it ? if yes, what is the safest way to schedule task in servlet ?

thanks,,,

Answer 1

Yes. It's perfectly safe. The servlet container will look after threads for HTTP requests, but you can spawn aditional threads yourself, whether their lifetime is restricted to that of the request, or for longer.

e.g. a common pattern is to spawn a long running processing thread. Servlet requests would put work items on a queue (for out-of-band processing) and the long running processing thread would handle these work items.

Here's an article from OReilly detailing timer usage in servlets and EJBs.

Answer 2

Yes, you can use Timers.

One important thing to remember is to cancel that Timer when the servlet is stopped. If you forget to cancel the Timer, your webapp will suffer from memory leaks (classloader leaks, since the Timer's Thread is bound to the WebappClassLoader via its ContextClassLoader) and cannot be deployed multiple times.