Using VisualAge for Java Enterprise Version 2 to Develop CORBA and EJB Applications

Moving to Enterprise JavaBeans 183

• WebSphere Application Server Libraries

• Sun JSDK Class Libraries

Notice at this point that you have some errors in the tea.business.cb package

because you do not have any of the Component Broker libraries loaded. We

have been unable to find any successful method of having the EJB and

Component Broker libraries coexist in VisualAge for Java. This is sure to

change as they are derived from the same code base. However, in the

versions that we used, they were incompatible.

There are also errors in several other TEA packages because of some

missing WebSphere function. To get around that, we will just import the

missing packages and classes from WebSphere into the IBM EJB Runtime

Support project. Copy the following packages and classes from the

WebSphere implementation into the IBM EJB Runtime Support project:

• com.ibm.jbroker package

• com.ibm.jbroker.ejb package

• com.ibm.CosNaming.TransientNameService class

If you are unsure of how to copy the packages and classes, consult the

VisualAge for Java help, or import Version 1.3 of the IBM EJB Runtime

Support from the repository supplied with the sg245276.zip file.

17.2 Changing the Existing Application

This time, to introduce the use of EJBs, we are going to change the

application by replacing the EmployeeID Component Broker object developed

in Chapter 16, “WebSphere and Component Broker Interoperability” on page

173 with an equivalent EJB. This EJB provides the exact same functionality. It

just covers our purpose of showing how to integrate EJBs in our application.

Among the different possible EJBs, we choose to implement a bean-managed

persistence bean.

17.3 Creating an EJB

Follow these steps to create an EJB:

1. Write a remote interface.

2. Write a home interface.

3. Write a bean.

4. Write a bean key.

184 Using VisualAge for Java Enterprise Version 2 to Develop CORBA and EJB Applications

5. Write a deployment descriptor.

6. Write a manifest file.

7. Package all these files in a jar file.

Fortunately, we can use VisualAge for Java and reduce our effort to develop

the bean class only. All other tasks are handled by the tool, which generates

all additional classes and even provides the final jar file ready for deployment.

And that is not all. Because WebSphere is packaged with VisualAge for Java,

we also have the runtime environment to deploy and test our EJB.

So, let us start from the VisualAge for Java Workbench and select the EJB

tab.

VisualAge for Java gathers EJBs into

groups

. To create a group, select the

EJBs->Add->EJB Group... menu item and fill in the fields as shown in

Figure 80.

Moving to Enterprise JavaBeans 185

Figure 80. Creating a New EJB Group

Select TEAGroup before adding an EJB.

An EJB consists of a number of Java classes and interfaces, such as the

bean class, remote interface, home interface, and a set of deployed classes.

You must manage all these classes as a single entity, so that they can exist in

synchronization. For example, if you need to delete a method from the bean

class, you want to ensure that the corresponding method in the remote

interface is deleted automatically. To manage all Java classes and interfaces

that belong to a bean as a single object, VisualAge for Java allows you to

create EJBs as first-class objects. In the Create Enterprise JavaBean

SmartGuide, you can define a name for the EJB and then define the

individual classes and interfaces that belong to that EJB. You can then

186 Using VisualAge for Java Enterprise Version 2 to Develop CORBA and EJB Applications

version the EJB as a single entity. For example, when you version an EJB, it

will version all of the corresponding Java classes and interfaces and save

their signatures into the EJB object. When a specific version of the EJB is

loaded, the correct version of all the EJB bean classes and remote and home

interfaces are loaded.

Follow these steps to add EJBs:

1. In the EJBs pane, select an EJB group to contain your EJB and click

mouse button 2.

2. From the pop-up menu, select Add - Enterprise JavaBean. The Create

Enterprise JavaBean SmartGuide appears (see Figure 81).

3. Click Finish, and VisualAge for Java will create four classes for you:

• EmployeeID interface

• EmployeeIDBean class

• EmployeeIDHome class

• EmployeeIDKey class

Figure 81. Creating an Enterprise Java Bean