Is init() really called once

[riohk kurn]

Sometimes, servlet container may create more than one instance of servlet, in this case, will these instances' init() be called.
As I have checked API, init() is not a static method, so it seems that init() will be called for each instance. However, what're inside init() should be shared with all instances, so, I'm just wondering.

[Rama Raghavan]

I think a review of the servlet lifecycle is in order.
The container does not create multiple instances of the servlet, but spwans multiple threads that calls the service() method, with only a single instantiation of the servlet. So - init() will be called (only) once.
EXCEPT- when the servlet implements SingleThreadModel, in which case init() could be called multiple times, based on a servlet pool managed by the container.
Rama

[riohk kurn]

Are there any containers create more than one instance depending to performance (but not singleThreadServlet)?

[Rama Raghavan]

NO.
Imagine if you have synchronized a block of code that updates an instance variable, say, count++.
ANY J2EE container must create only one instance of my servlet, otherwise, I cannot rely on a supposedly thread-safe code.
Rama