Re: how servlet works ?
Juha Laiho wrote:
Nope; with SingleThreadModel the container is allowed to (and at least
Tomcat does) instantiate multiple copies of the servlet based on the
amount of requests. The "one is served, others wait" is what happens
if you synchronize the service method in the servlet (DON'T DO THAT!).
Manish Pandit wrote:
From Servlet Spec 2.4, page 219:
SRV.14.2.24 SingleThreadModel
public interface SingleThreadModel
Deprecated. As of Java Servlet API 2.4, with no direct replacement.
Ensures that servlets handle only one request at a time. This interface
has no
methods. 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, or
by maintaining a pool of servlet instances and dispatching each new
request to a
free servlet.
No contradictions there. Juha pointed out that the programmer should not
synchronize the service method; nothing about forbidding the container to.
Juha pointed out that the container may use multiple servlet instances, same
as the servlet spec says.
A container that synchronizes access to a single instance's service() would be
at a performance disadvantage to those that use multiple instances, as "at
least Tomcat does", and likely therefore a competitive disadvantage.
- Lew