In contrast to stateless session beans, stateful session beans maintain state for an individual client over one or more method requests. A stateful session bean is not shared among clients, and a client's reference to a bean only ends when the client ends the session or the session times out. The state is not written to a database but held in the containers cache and is lost when the container crashes.

The classic example of a stateful session bean is the online shopping cart. The user adds one or more items to a shopping cart, possibly over a long time period while the user visits other web sites or is interrupted by a phone call. Finally the user may decide to purchase the items in the cart, cancel his or her shopping cart session, or even abandon the session without explicitly terminating it.

The following example illustrates some aspects of a shopping cart. Our shopping cart will be limited to adding items to a cart and listing the current contents of a cart. First...