Anurag RANA

EJB 3.0, entity bean used in EJB 2.0 is largely replaced by persistence mechanism. Now entity bean is a simple POJO having mapping with table. Following are the key actors in persistence API − Entity  − A persistent object representing the data-store record. It is good to be serializable. EntityManager  − Persistence interface to do data operations like add/delete/update/find on persistent object(entity). It also helps to execute queries using  Query  interface. Persistence unit (persistence.xml)  − Persistence unit describes the properties of persistence mechanism. Data Source (*ds.xml)  − Data Source describes the data-store related properties like connection url. user-name,password etc. To demonstrate EJB persistence mechanism, we need to do the following tasks − Step 1  − Create table in database. Step 2  − Create Entity class corresponding to table. Step 3  − Create Data Source and Persistence Unit. Step 4  − Create a stateless EJB having EntityManager instance. Step 5  − Update s