Question

I write couples of servlet program, however I dont think I fully understand how servlet run. So here is couples question that I have:

All the code I wrote about Servlet only run on Netbeans with apache tomcat run behind. When I run my html file that make request to the servlet, it usually give error saying that it could not find the servlet, I then have to redeploy the servlet then everything would run fine. Seem like my servlet timeout after a while or something.

Does the servlet run all the time? Servlet has init() and destroy(), so I guess it wont run all the time. So then when does it start and when does it end? Does it start when there is a request from the client, and end when it is time out? And how does I fixed my problem that I have to constantly redeploy the servlet. Thank you very much.

Answer 1

Under normal circumstances, a servlet is only destroyed at shutdown (ie when the application container, such as Tomcat, is shut down). Otherwise it remains in memory for the duration of the application. I couldn’t say what’s going on with your Netbeans setup, but try deploying your WAR file to a standalone Tomcat installation and see if the problem doesn’t go away.

Another time that the application container will call destroy on a servlet is if it is running out of memory, but this is far less common.

Regarding your question about requests, a servlet is designed to handle many requests. It is said that the servlet is application-scoped, whereas the request has its own scope.