Application clients

Java client applications require servlets, residing on the same machine as WAS, to communicate with EJBs.

The following client types are available:

  1. J2EE application

    Provides the benefits of the J2EE platform for the Java client application.

    Most common configuration for large-scale enterprise business systems.

    Uses the application client run time to configure execution environment; uses the JNDI name space to access resources; runs on client machines and directly accesses enterprise beans, JDBC APIs, and JMS message queues.

  2. Pluggable and thin application

    Used in situations where a Java client application exists but the application needs enhancements to use enterprise beans, or where the client application requires a thinner, more lightweight environment than the one offered by the J2EE application client.

    The thin application client includes a JVM, and uses the IBM Developer Kit for the Java platform. The pluggable application client requires the user to provide a JVM. The pluggable application client uses the Sun JDK for the Java platform.

  3. ActiveX application

    Uses the JNI architecture to programmatically access the JVM API. Therefore the JVM code exists in the same process space as the ActiveX application (Visual Basic, VBScript, or ASP files) and remains attached to the process until that process terminates.

  4. Applet

    A Java applet embeds in a HTML document residing on a remote client machine from the WAS. With this type of client, the user accesses an enterprise bean in the WAS through the Java applet in the HTML document.

The application client run time supplies a container that provides access to system services for the client application code. The client application code must contain a main method. The application client run time invokes this main method after the environment initializes and runs until the JVM code terminates.

The J2EE platform supports the application client use of nicknames or short names, defined within the client application deployment descriptor. These deployment descriptors identify enterprise beans or local resources (JDBC, JMS, JavaMail and URL APIs) for simplified resolution through JNDI. This simplified resolution to the enterprise bean reference and local resource reference also eliminates changes to the client application code, when the underlying object or resource either changes or moves to a different server. When these changes occur, the application client can require redeployment.

The application client also provides initialization of the run-time environment for the client application. The deployment descriptor defines this unique initialization for each client application. The application client run time also provides support for security authentication to enterprise beans and local resources.

The application client uses the Java Remote Method Invocation-Internet InterORB Protocol (RMI-IIOP). Using this protocol enables the client application to access enterprise bean references and to use CORBA provided by the J2EE platform implementation. Use of the RMI-IIOP protocol and the accessibility of CORBA services assist users in developing a client application that requires access to both enterprise bean references and CORBA object references.

When you combine the J2EE and CORBA environments or programming models in one client application, understand the differences between the two programming models to use and manage each appropriately.

View the Samples gallery for more information about application clients. Before you run the basicCalculator sample, verify that the Java Messaging Service (JMS) server is started.


See Also

Application client functions