Presented by developerWorks, your source for great tutorials

ibm.com/developerWorks

Section 4. Example 1: Defining CMP fields

Defining CMP fields in the local interface

The first step is to define CMP fields. A CMP field is a field you want the EJB container

to persist. An entity bean has CMP fields that are virtual fields. Unlike CMP 1.0, in CMP

2.0 you don t define member variables for CMP fields. Instead, using the JavaBeans

property naming convention, you define virtual getter and setter methods

corresponding to name of the fields that you want to persist. You add these abstract

methods in both the interface and the implementation. This concept is demonstrated in

the following code:

package com.rickhightower.auth;

import javax.ejb.EJBLocalObject;

public interface LocalUser extends EJBLocalObject {

public String getEmail();

public String getPassword();

}

Since you only defined getters for the

UserBean

 s e mail and password CMP fields,

they are both considered read only fields. Conversely, the implementation entity bean

must defined both getters and setter methods for the properties, even though the

properties are read only. This is covered in the next panel.

Defining CMP fields in the entity bean class

(implementation)

Unlike the local interface the implementation entity bean class must defined both

getters and setter methods for the CMP fields, even though the CMP fields are

read only. The getter and setter methods for the CMP fields are abstract methods since

there implementation will be defined by the EJB container. The code for the

implementation class is as follows:

package com.rickhightower.auth;

public abstract class UserBean implements EntityBean {

public abstract String getEmail();

Introducing EJB CMP/CMR, Part 1 of 2

Page 13 of 48