JAX-WS Web服务线程模型

Question

(1) Okay I am pretty confused about the threading model of JAX-WS Java web services. I read they are not thread-safe. How are they supposed to serve multiple parallel requests then? Given that its always known (mostly) they are going to get called from multiple clients at the same time.

(2) And does the app server create a new instance of web service for each request (like it maintains a pool of stateless session beans, assigns one out for a request and once the request completes, it is returned to the pool). can you configure that pool size in app server console (GlassFish or JBoss or WebSphere).

(3) And I also found out about @Threadsope annotation here which creates new thread per request..
http://jax-ws-commons.java.net/thread-scope/
Is that a good option? I am sure people are solving the thread-safety and parallel requests issues in some other standard way - please advise.

Answer 1

An application server contains a pool of beans.
When working with stateless session bean, it is not guaranteed you will get the same instance across working with the session.
However, since as I mentioned, the beans are managed by a pool, holding a state in them, is a bad idea.
I don't think that EJB beans have anything to do with what your need, though.
Pay attention that in the example you provided, Both DataService and the connection are created per request. This is a bit expensive.
I would consider using the ThreadLocal API only for the connection, and have it obtained from a connection pool.
You can implement these on your own, by reading about ThreadLocal and by reading about DB connection pools.


To conclude - I don't think EJBs are relevant here.
Don't hold both your service class and the fields at the thread local, but only the necessary fields you will allocate per request. (in the example you showed - it's the connection)