Building Java Applications for the iSeries Server with VisualAge for Java 3.5

370 Building Java Applications for the iSeries Server with VisualAge for Java 3.5

Figure 9-32 Host application successful start

We are now ready to run the client application. Both the registry and the host application are

started.

After executing the client application, perform the following tasks:

1. Enter the iSeries system name, user ID, and password. Click Connect.

2. After the Connected to AS/400 message appears, complete the following steps:

a. Enter a part (item) number and click the Get Part button. Valid numbers are 12301

through 12350.

b. Click the Get All Parts button to display all the records in a table.

9.5 Moving the Order Entry server application to Java

So far, we have shown you how to move the user interface for the Order Entry application to a

client PC using Java. We have demonstrated how to do this while reusing much of the existing

RPG application. Now, we are ready to replace the RPG application with a Java version. The

primary benefit of this is to gain easier maintenance and portability of our application.

Next, we migrate the Order Entry application to Java on iSeries. We use the Java remote

method invocation interface to allow the client Java program to interface with the server Java

code. Figure 9-33 shows the new design.

Java Shell Display

initialize:new

Main: Attempting to register JDBCRmi

Main: Successfully registered with the RMI

===>

F3=Exit F6=Print F9=Retrieve F12=Exit

F13=Clear F17=Top F18=Bottom F21=CL command entry

Chapter 9. Moving the server application to Java 371

Figure 9-33 Java client/Java server Order Entry application

This section explains the Java code that is necessary to replace the RPG Order Entry

application. We discuss two techniques: how to use record-level access and how to use

JDBC. We also discuss the changes that are required for the client code.

There are three approaches to creating Java on iSeries for the Order Entry application:

򐂰 We can simply create a procedural Java program and make all variables and methods

public. This is the most straightforward way of moving to Java, but it does not take

advantage of any of the object-oriented constructs, such as encapsulation.

򐂰 We can completely redesign the application to be fully object-oriented. This involves

creating classes to encapsulate all of the files that are used, a class to hide the data queue

implementation, and classes to describe an order and a customer.

򐂰 We can compromise and use object-oriented constructs where it seems sensible to do so

and still use a somewhat procedural coding style for the primary methods.

We have chosen to take the third approach, because it seems to be easier to understand as a

first step in moving to Java. We use classes to describe the Order Entry application and the

order itself. We also hide the internal implementation of the Order Entry class.