Entity Beans

Entity Beans

Entity Bean  

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Models data Represents real data objects, such as customer, products, or employees Does not contain business process logic Knows how to persist itself

Features    

Long-lived Survive failures View into data store Single Threaded

Entity Bean’s Components 

Remote interface 

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Home interface 

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Interface to entity beans class on which clients invoke Clients create, find, and destroy entity beans

Bean class 

Models persistent data

Entity Bean’s Components 

Primary bean class 

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Unique identifier for your entity bean

Deployment descriptor  

Contains entity bean’s properties Properties will be used by the container

Entity Beans 

Two ways to persist entity beans:  

Bean-Managed Persistent (BMP) Container-Managed persistent (CMP)

BMP 

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Developer must handle the persistence Developer must write code to take the in-memory data and store them into an underlying data store

CMP 

The container/server handles the persistence layer

Creating Entity Bean ejbCreate() Is used to create underlying data  May have different parameters  Must have a corresponding create() method in home interface Example: 

public AccountPK ejbCreate(String accountID, String owner) … public Account ejbCreate(String accountID, String owner) …

Finding Entity Beans – ejbFind() All finders start with ejbFind  Must exist at least one called ejbFindByPrimaryKey()  May have different names and parameters Example: 

public Enumeration ejbFindAllProducts() … public Enumeration findAllProducts() …

Destroying Entity Beans – ejbRemove()  

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Will remove the database data Has a corresponding remove() method in home interface Will not be called if entity bean times out

Entity Context – setEntityContext() 

Represents the environment of the entity bean

getEJBObject() 

Returns the EJBObject associated with the entity bean

getPrimaryKey() 

Identifies which database data the entity bean is associated with