Head First EJB

Session bean create() vs. entity bean create()

1. Stateful session bean create()

   • Client calls it to get an EJB object reference to a new just-for-me stateful session bean.

   • It can (and frequently does) have arguments, that the bean uses to do client-specific initialization (before running any business methods).

   • The Container makes a new session bean when the client calls create()

2. Stateless session bean create()

   • Client calls it to get an EJB object reference to a bean

   • It has no arguments, and the bean does not do any client-specific initialization (since at the time the bean’s ejbCreate() is called, the bean has no association with a client!)

   • The Container does not make a new session bean when the client calls create(), and does not pull one out of the pool until the client invokes a business method.

3. Entity bean create()

   • Client calls it to insert a new row in the database!* Although the end result for the client is still an EJB object reference (in this case, to the newly-created entity).

   • It will virtually always have arguments (although they aren’t mandatory, but it’s kinda hard to imagine a create() without them... like, “Hey database, create a new customer... no, I don’t have any name or ID or anything... just make some stuff up”).

   • The Container does not make a new entity bean, but it does pull one out of the pool to run the ejbCreate() method. Remember, the ejbCreate() method has to take the create() arguments and somehow create a new entity in the underlying persistent store (or at least support ...