EJB Logical Architecture
|
EJB Logical Architecture |
|
· A EJB system is logically a three-tier system · The three tiers are as follows: a) The Client b) The EJB Server c) The Database (or other persistent store) · This is a logical architecture because these tiers don’t necessarily have to reside on three different machines. · For example, a) The EJB server and the database might reside on the same machine, when the EJB server includes built-in functionalities for persistent storage. b) The client and the EJB server might reside on the same machine, when an EJB bean makes a call to another bean in the same container. The caller bean is acting as a client here. c) These two cases can be combined to have all the tiers in a single machine. · EJB’s role in each of these tiers are: a) A program on the client side makes call to remote EJBs. The client needs to know how to find the EJB server and how to interact with the objects that reside on the EJB server. b) The EJB components live in the middle tier. The EJB objects reside inside an EJB container, which in turn resides in an EJB server. c) EJB can access the database themselves, typically via Java Database connecting (JDBC), or they can allow the container to handle their data storage needs for them.
|
