Question regarding SingleThreadModel

[Gaurav Chhabras]

In one E - Book i have read that -:

" Recall that multiple client requests to the same servlet result only
in multiple threads calling the service method of a single servlet instance.
They do not result in the creation of multiple servlet instances except possibly when the servlet implements SingleThreadModel."

In above it is written that it will create multiple instance of Servlet if we implements SingleThreadmodel, but i think that only one instance of servlet is created , so how is it possible that many instance of one servlet will be created, it will nullify the usuage of servlet if it will create many instance of the same servlet.

Thanks
Regards
Gaurav

[Mani Ram]

From the Java API on SingleThreadModel

If a servlet implements this interface, you are guaranteed 
that no two threads will execute concurrently in the servlet's 
service method. The servlet container can make this guarantee by
synchronizing access to a single instance of the servlet, 
[I]or by maintaining a pool of servlet instances and 
dispatching each new request to a free servlet. [/I]

As you can see, whether to create a single instance (and to provide a synchronized access) or to create multiple instances, depends on the implementation of the Servlet container.
But if multiple instances are created, the containers generally pool them to improve the performance.
[ November 23, 2005: Message edited by: Mani Ram ]

[Ben Souther]

Gaurav,

This thread from last week might interest you.
In it, singleThreadModel was discussed quite a bit.

http://www.coderanch.com/t/361606/Servlets/java/Pooling-Servlet