Head First EJB

Compared to stateful beans, stateless beans have a simple life

Stateless beans have a much simpler existence. They’re born (created), they’re thrown into a pool with others of their kind, they run business methods for any client who asks, and they might eventually die. They aren’t passivated, they don’t keep client-specific state, and their creation and destruction (removal) aren’t tied to the whims of the client. Compare the difference between the lifecycle of a stateful vs. stateless bean:

The bean lifecycle (special moments in a bean’s life)

Stateful session beans

• Bean creation (when the client wants a bean)

• Bean use (when the client calls a business method)

• Bean passivation (the bean is put to sleep to conserve resources)

• Bean activation (the bean wakes up to service a business method from the client)

• Bean removal (when the client is finished with the bean or the bean times out)

Stateless session beans

• Bean creation (when the container wants to make a bean)

• Bean use (when the client calls a business method)

• Bean removal (when the container decides there are too many beans in the pool, or the bean throws a system exception.)

Comparing the lifecycles of stateful and stateless session beans

Stateful

Stateless

Client calls create on a stateless session bean home

1. Client calls create on the home.

2. Container ...