Chapter 13 Creating CORBA-Compatible Java Clients

Deploying Java clients

This section describes how to deploy Java applets and applications, and lists the classes required by the Jaguar Java client ORB.

Deploying applets

To deploy a Java applet, you must create an HTML page that loads the applet. The HTML file and all classes used by the applet must be made available for download from the Web server. Typically, you create a Java archive (JAR) file that contains all required classes, and then reference the JAR file from the HTML page. You can also copy the required classes to the Web servers class tree. (For Jaguar, the class tree is the html/classes directory).

Building a JAR file containing all necessary classes usually offers better performance than specifying a code base directory, since the client opens only one connection to download all classes that are required. When classes are downloaded individually, Web browsers typically open multiple connections to download each class, and performance suffers, compared to the single JAR file download. Some development tools, such as PowerJ, can determine class dependencies and create a JAR file for you. If you create a JAR file manually, add the classes listed in "Required classes".

You must also decide whether to deploy the HTML page and the applet on Jaguar's built-in Web server or on another Web server. Deploying both HTML and class files on Jaguar is the simplest scenario, unless your HTML page requires dynamic HTML, server-side includes, or other features that are not supported by Jaguar's HTTP server. In this case, you must deploy the HTML on a separate Web server and the classes on Jaguar. Since the classes are on a separate server, you must use a full URL with host and port names when specifying the code base in your HTML file. For example:

<applet 
codebase="http://agogo:8080/classes"
code="Sample/Demo/MyClient.class">
</applet>

In this example, the applet classes will be downloaded from another server that accepts HTTP requests on the machine agogo at port 8080. You must deploy the applet's Java package directories and class files under that directory.

Beware of the security constraints on the network connections made by your applet. By default, applets cannot open network connections to hosts other than the host from which they were downloaded. If necessary, end users can reconfigure their browsers and change the security constraints. In practice, it is easier to deploy applications that work within the default security constraints rather than asking end users to change their configuration. You will have no problems if your applet classes are downloaded from Jaguar and connect back to the same Jaguar server.

If your end users are connecting to the Jaguar server through a corporate firewall, HTTP tunnelling may be required. Some firewalls do not allow IIOP connections. As described in "HTTP tunneling support", the Jaguar Java ORB performs tunnelling automatically when required. If you are certain that tunnelling is required, you can set the com.sybase.CORBA.http property to true so that connection attempts do not try IIOP before switching to HTTP-tunnelled IIOP.

If your applet connects to a secure IIOP port, you must make sure that the deployment server is configured with the necessary certificates to allow SSL connections to be made from your applet to the Jaguar server.

Deploying applications

To deploy a Java application, you can create a JAR file that contains all classes required to run the application. Users can copy this file to their machine, add its location to the CLASSPATH system variable, and then run the application with the JDK Java interpreter. You may want to supply a script that configures the environment and runs your application with any required command-line parameters.

The JAR file must contain the classes listed in "Required classes".

Required classes

In addition to the classes that implement your client program, you must ensure that the classes below are deployed with your applet or application.

 

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