Developing client applications

A client application performs business logic and makes use of the framework provided by an underlying client. Developing the code for a client application depends on the objects and functions you want to exploit, and the programming model that you want to use.

1. Choose the type of client that you want to use as a framework for your client application.
   Decision factors for choosing a client include whether you want to run a client application on Java EE or J2SE; whether you want ease of use with a small installation footprint or full-function with medium-large footprint; and whether you need licence to copy or redistribute the client.
2. Develop the client application code.
   The following substeps are a high-level general procedure. Information specific to a type of client is given in the related tasks.
   1. Create an instance of the object that you want to access on the remote server.
      You can use full Java™ Naming and Directory Interface (JNDI) support to get a suitable reference to administered objects from the server's JNDI namespace. Alternatively, you can get suitable references to objects programmatically without using JNDI.

      Using the javax.naming.InitialContext class, the client application program uses the lookup operation to access the Java Naming and Directory Interface (JNDI) namespace. The InitialContext class provides the lookup method to locate resources.

      You can compare the use of JNDI and programmatic techniques by looking at the samples provided for the Java EE client and Java thin client in an Application Client installation (for example, in C:\wac70\samples\src\):

      • Java EE client use of JNDI for BasicCalculatorHome: TechnologySamplesJ2EEClient\BasicCalculator\com\ibm\websphere\samples\technologysamples\basiccalcclient\BasicCalculatorClientJ2EE.java
      • Java thin client programmatic retrieval of BasicCalculatorHome: TechnologySamplesThinClient\BasicCalculator\com\ibm\websphere\samples\technologysamples\basiccalcthinclient\BasicCalculatorClientThin.java
   2. Create a connection to the server.
      If the server runs with security enabled, you can configure secure connections.
   3. Work with the objects to perform your business requirements.
      For example, send and receive JMS messages, update database entries, handle error conditions, and close resources used.
3. Compile or assemble the client application.
   This creates the JAR or EAR file that you can deploy to make the client application available for use.

   To compile your client application, include the JAR files needed in the CLASSPATH setting for the javac command; for example, any extra JAR files for the client application's own classes, JAR files for IBM® Thin clients used, and JAR files for JDBC provider classes.

   Attention: IBM-provided clients are not packaged with JDBC provider classes. For example, the WebSphere Application Server Version 7.0 Java Thin application client is not packaged with Apache Derby 10.2 classes. If your client application needs to use a database class (such as through the JNDI lookup of a datasource), you must obtain the class files from the database provider and make them available when compiling and running the client application.