public void setEntityContext(javax.ejb.EntityContext aContext) {

	context=aContext;

}

public void ejbActivate() {

}

public void ejbPassivate() {

}

public void ejbRemove() {

}

public void unsetEntityContext() {

	context=null;

}

public void ejbLoad() {

}

public void ejbStore() {

}

The purposes of these methods in a BMP entity bean are described in TABLE 6-1. (For comparison, see TABLE 4-2.)

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Completing Your BMP Entity Bean

To complete your BMP entity bean, do as follows:

• Add all persistence logic.
• Add a primary key class if your BMP entity bean has a composite primary key.
• Define a create method if you want clients of your bean to be able to insert data into the database. An entity bean can have more than one create method.
• Define any finder methods that your BMP entity bean needs besides findByPrimaryKey, and code the bodies of all the finder methods.
• Code the ejbRemove method to remove the appropriate record from the database.
• Define and code all business and home methods that your BMP entity bean needs.
• Add private fields to maintain your entity's state in memory and populate the values of these fields.

Using Recommended Approaches When Working With Enterprise Beans

Appendix A discusses the best ways to make changes in your enterprise beans, and the errors and anomalies that you might see if you use other approaches. As a general rule, you should work through the logical node rather than the individual class nodes, use the bean's property sheets or the Customizer dialog box to edit methods, and use the IDE's Source Editor to complete or edit any bean code that isn't available to you through one of the dialog boxes.

Adding Persistence Logic

To make your BMP entity bean interact with the entity data store, you must write code to access the data, manipulate persistent fields, and transfer data between your bean instance's variables and the data store. Use the Source Editor to write your code. Use resource references (as discussed in Chapter 8) to specify the data source that your bean will use.

Adding a Primary-Key Class

Use the Source Editor to add a primary-key class if:

• You didn't create a primary-key class when you created the BMP entity bean, and your bean needs one.
• You need to specify a primary key that can't be represented by any existing class.
• Your primary key has a type other than java.lang.String or an existing primary-key class.
• You must customize the definition of the equals and hashcode methods.
• You want to wrap the primary key with some extra functionality, such as testing the key for valid values before it is used with the database.

Make sure your primary-key class meets the following requirements:

• The class has the access-control modifier public.
• All fields are declared as public.
• The class has a public default constructor.
• The class implements the hashCode and equals methods.
• The class is serializable: It implements the java.io.Serializable interface.
• The class does not implement the java.rmi.Remote interface.

For more information, see the discussion in Adding or Replacing a Primary Key.

Adding Methods

To start defining a new methods, go to the Explorer, right-click the logical bean node, and take advantage of the GUI tools that are available from the contextual menu. Use the dialog boxes to name a method and define its signature. The IDE propagates your method automatically to the correct classes. Then finish coding your method within the Source Editor.

Defining Create Methods

The home interface of your BMP entity bean can have a create method, and, if so, the bean class must have corresponding ejbCreate and ejbPostCreate methods. When you use the recommended process, the IDE ensures that these methods are generated and propagated correctly.

The ejbCreate method in a BMP entity bean typically does the following:

1. Validates client-supplied arguments

2. Initializes the instance's variables

3. Executes SQL Insert statements (or you can call another class, such as a DAO, to insert data into the underlying data store)

4. Returns a primary key

In a BMP entity bean, you must provide the code that generates and executes the necessary SQL Insert statement.

The ejbPostCreate method, which the IDE adds automatically, gives the programmer the opportunity to forward information about the EJB object (such as the home or remote interface) to any other enterprise beans that need to reference it. The method can access the remote interface through EntityContext, which it receives from the container as a parameter. This method is typically used to create dependent beans. For example, the Order bean's ejbCreateLineItem method might create the given line items in the ejbPostCreate method.

Your entity bean can have more than one create method. Define a new create method as follows:

1. Select the logical node, right-click, and choose Add Create Method.

The Add New Create Method dialog box appears.

2. Name your create method, using any extension after create.

Now you need to add parameters to your method.

3. In the dialog box, click Add.

4. In the Enter Method Parameter dialog box, specify the parameter's name and type.

Both the method signature in a BMP entity bean class and the method body return the primary-key type.

5. Click OK to dismiss the Enter Method Parameter dialog box.

6. In the Add New Create Method dialog box, specify any additional exceptions.

7. Click OK to dismiss the Add New Create Method dialog box.

The method you added now appears in the bean class code as ejbCreate and in the home interface as create. The method ejbPostCreate also appears in the bean class.

8. Use the Source Editor to add the return statement and all other necessary code to your new create method.

Adding Finder Methods

The EJB Builder has already generated a default finder method for you. In a BMP entity bean, this method shows up in both the home interface (findByPrimaryKey) and the bean class (ejbFindByPrimaryKey). However, if you want your entity bean to execute additional queries, you must define additional finder methods.

If you follow these steps, your new finder method is automatically propagated to your home interface and bean class:

1. Select the logical node, right-click, and choose Add Finder Method.

2. Type a name for the method starting with find. Specify parameters, exception, and a return type. Click OK when you're finished.

Finish coding your finder method or methods using the Source Editor. To fetch primary keys from the data source, you must write JDBC code or use other means of database access.

Defining Business and Home Methods

To add a business method to your BMP entity bean, do as follows:

Under the logical node, select Business Methods, right-click, and choose Add Business Method.

The Add New Business Method dialog box appears. At this point you can finish coding the method's parameters and exceptions in this dialog box, or you can simply type a name for your new business method, click OK, and finish the coding in the Source Editor.

A business method typically accesses and modifies the values of persistent fields, but it doesn't directly access the database. The EJB container calls the ejbLoad and ejbStore methods as required by the semantics of the transaction.

Alternatively, you can add a home method to perform an operation that does not depend on any given instance of the entity bean. See Defining Home Methods for a discussion of home methods.

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After Creating Your BMP Entity Bean

Your BMP entity bean is now finished except for a few steps by which you prepare the bean to work in its eventual environment. These final steps are described in Chapter 8.

Recommendations for working with finished enterprise beans are given in Appendix A.

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Further Reading

Enterprise beans can be a very powerful and flexible part of your application. Creating the basic parts of an enterprise bean can be very simple, especially with a tool like the Sun ONE Studio 5 IDE. However, completing the bean so that it fulfills the needs of your application can be very complex. For details, refer to Enterprise JavaBeans Specification, version 2.0 at:
http://java.sun.com/products/ejb/docs.html

The J2EE Tutorial contains useful advice for developing BMP entity beans. Go to http://java.sun.com/j2ee/tutorial/1_3-fcs/doc/BMP.html for examples and instructions.

You might also refer to Advanced Programming for the Java 2 Platform by Calvin Austin and Monica Pawlan at: http://developer.java.sun.com/developer/onlineTraining/Programming/JDCBook/bmp3.html