Head First EJB

What can go wrong?

1. In the Bean

   • The business logic in a method realizes that it cannot do its job because of a problem the client expects. For example, a banking bean can’t do a balance transfer, because the ‘transfer from’ account doesn’t have any money!

   • The bean catches a checked exception while running business logic. For example, the bean fails to get a JDBC connection, or a JNDI lookup throws a NamingException to the bean. This is a problem that the bean expects, but the client doesn’t.

   • A method in the bean (or a method the bean calls) throws a runtime exception (like NullPointerException) that the bean doesn’t catch, and the client doesn’t expect.

2. In the Container

   • The Container can’t complete an operation for which its responsible, such as updating the state of an entity bean in the database, that causes a problem the client expects.

   • The Container catches a checked exception thrown by the bean, that the client expects.

   • A Container catches a runtime exception thrown by the bean, or by some other object the Container interacts with. This is a problem that the client does not expect.

3. In the RMI subsystem, or some other part of the communication path between client and container.

   • The EJB object throws a runtime exception before it communicates with the client about the result of a client’s business method call to the bean.

   • The RMI subsystem can’t communicate with the client.

   • The client stub throws a runtime exception, or a RemoteException while trying to send a method call, or receive a return ...