EJB - Entity Beans I
3 April 2008This post contains an introduction to Entity Beans.
An entity beans are used to represent a business object in a persistent storage mechanism for example: customers, orders, products, employees etc. We normally refer persistent storage mechanism as a relational database. Normally, each entity bean has an underlying table in a relational database. Please note that each instance of the bean corresponds to a row in that table.
Some people mix Entity beans with session means. Both are different in many ways. Some properties of Entity beans are listed below which are not present in Session beans:
- persistent
- shared access
- primary keys
- may participate in relationships with other entity beans
Lets talk about persistence. The state of Entity bean is saved in a storage mechanism, therefore it is persistent. It means that the entity bean’s state exists beyond the lifetime of the application or the J2EE server process. You all know that the data in a database is persistent because it stays even after database server or the applications are turned off/shutdown.
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