Develop a Java EE client application

Develop code for a Java EE client application.

Tasks

1. Write the client application program. Write the Java EE client application on any development machine. At this stage, we do not require access to the WebSphere Application Server.

   (ZOS) Rules: If we are writing a client application program that will run on z/OS, the following rules apply:

   • Client programs may start their own transactions but cannot join in or start transactions in the WAS for z/OS run-time.
   • Client application code must contain a main method.
   • All input and output files for the client application must be in ASCII, because the client run-time runs in an ASCII JVM.

2. Assemble the client application JAR file using an assembly tool.

   The JNDI namespace knows what to return on a lookup because of the information assembled by the assembly tool.

   Assemble the client application on any development machine with the assembly tool installed.

   When we assemble the client application, provide the required information to initialize the runtime environment for the client application. For information about how to provide the required information, see the documentation for the assembly tool.

   When we configure resources for use by the client application, consider the following items:

   • Resource environment references are different than resource references. Resource environment references enables the client application to use a logical name to look up a resource bound into the server JNDI namespace. A resource reference enables the application to use a logical name to look up a local Java EE resource. The Java EE specification does not specify a particular implementation of a resource. The following table contains supported resource types and identifies the resources to which the WAS provides a client implementation.

     Resource Type	Client Configuration Notes	Client implementation provided by WAS
     javax.sql.DataSource	Supports specification of any data source implementation class	No
     java.net.URL	Supports specification of custom protocol handlers	Provided by Java Runtime Environment files
     javax.mail.Session	Supports custom protocol configuration	Yes - POP3/POP3S, SMTP/SMTPS, IMAP/IMAPS
     javax.jms.QueueConnectionFactory, javax.jms.TopicConnectionFactory, javax.jms.Queue, javax.jms.Topic	Supports configuration of WebSphere embedded messaging, IBM MQ Series and other JMS providers	Yes - WebSphere embedded messaging

3. Assemble the Enterprise Archive (EAR) file.

   The application is contained in an enterprise archive (EAR file). The EAR file is composed of:

   • Enterprise bean, application client, and user-defined modules or JAR files
   • Web applications or WAR files
   • Metadata describing the applications or application XML files

What to do next

After developing the Java EE client application code, deploy the application onto the client machines where the client application is to run.

Subtopics

• Java EE client application class loading
  When we run your Java EE application client, a hierarchy of class loaders is created to load classes used by the application.
• Assembling Java EE client applications
  Application client projects contain programs that run on networked client systems. An application client project is deployed as a JAR file.

Related:

Development and assembly tools

Deploy a Java EE client application