Is EJB pooling related with flyweight pattern ?

Question

SCEA training exam from www.javaqueries.com says that
Bean pooling allows container to use beans as flyweight.
My opinion is that flyweight pattern allows to create an object (flyweight) with some common state. All other objects have references to the flyweight instead of having many copies of a common state.
Do you see any similiarity with EJB pooling ?

Answer 1

A container is pooling stateless session beans in a way that is very similar to the flyweight pattern.
The flyweight pattern describes situations where you need a fine granularity in your objects but instantiating all of these objects would be too costly to realize in terms of main memory or execution time. The solution is, instantiate only as many objects that do differ in their "intrinsic" state and share the instances all over the references. GOF have a simple yet powerfull example: Think of flyweight objects as the letters in a Texteditor. Instantiating each letter as a single object would be overkill. Just instantiate one object for each letter of the alphabet and reference these objects where needed in the text flow. The same for stateless session beans. Only instantiate beans that are different and share references to the same bean every time a create method is called for a stateless session bean.
That is very contrary to the statefull session beans or entity beans so these can not naively be implemented as flyweight. But maybe there are some special extension to the flyweight pattern so that they can?
Hope that helps...
Stephan