ENTITY BEAN IN JAVA Hiren Jamod Department Of ComputerScience Saurastra University-Rajkot
ENTITY BEANS Enterprise Beans which represent persistent data stored in a storage medium, such as a relational database. Persists across multiple sessions and can be accessed by multiple clients. Each instance of the entity bean represent a row in the table EJB container creates instances of an entity bean and is responsible for loading data in an instance and storing the information (data) back into the database.
ENTITY BEANS The persistent mechanisms that enable you to perform these database manipulations, such as serialization, Object/Relationship (O/R) mapping to a relational database and support for JDBC are built-in the entity bean model
CHARACTERISTICS Persistence Implies that its state exists even after a client stops accessing an application The persistent data remain intact even after the storage shuts down Shared Access Multiple clients can share one entity bean by using separate instances of the entity bean EJB Container maintains data consistency by synchronizing entity bean instances with the database To maintain data consistency, the entity beans work within a transaction
CHARACTERISTICS Primary Key Each Entity bean has unique identifier; is known as Primary Key that enables the client to locate the exact entity bean Relationships Like the data of a relational database, the entity beans are also elated to each other
LIFE CYCLE OF ENTITY BEANS Initially, the beans do not exist When the Application server this stage to the Pooled stage When the server is first started, several bean instances are created and placed in the pool. A bean instance in the pooled state is not ties to particular data At this stage, the beans are referred as passivated. The bean remains in this stage till the client does not make a request for it or the container does not activate it.
LIFE CYCLE OF ENTITY BEANS The bean’s business methods can be invoked when the bean is at the ready stage. It remains at this stage till the client calls its remove method or the container passiveness it if the bean has been lying idle for sometimes