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Using the AppletArchiver to create a .jar or .cab archive

Contents: What the AppletArchiver does; How to create an archive with the AppletArchiver; Examples; Change history

What the AppletArchiver does

When you are serving applets from an HTTP server, you can increase the speed at which your applet loads by archiving the classes and resources needed by the applet into a .jar or .cab file. WebLogic supplies a utility, called the AppletArchiver, to help you create such a file.

The AppletArchiver utility loads and views applets in a separate window, remembers all of the remote classes and resources loaded by the applet, and when the window is closed, packages these classes in either .jar or a .cab file format. This document explains how to use the AppletArchiver utility to create an archive file, where to store the archive on your WebLogic Server, and how to refer to the archive in your applet's APPLET tag.

Not all browsers can use .jar/.cab-type archives. Here are the browsers that are archived-enabled:

Netscape browsers after version 3.0 -- .jar files only
Microsoft IE browsers after version 4.0 -- .cab files only

You can create both types of archives for your applet and include both filenames in the APPLET tag. Browsers that do not read either type of file can load your applet classes individually, using the CODE and CODEBASE that you have set.

Note that creating a .cab file requires the presence of the Microsoft SDK (specifically the cabarc.exe tool). You can get this directly from Microsoft. The jar archiver is distributed with the JDK.

How to create an archive with the AppletArchiver

Load your applet on a webserver, like the WebLogic Server. (There is more on how to do this in Using WebLogic for applet programming.
Unset your CLASSPATH in the environment in which you plan to run the AppletArchiver. This is to ensure that the tool doesn't load classes locally from your CLASSPATH; it forces the tool to load all the classes it needs from the webserver.
You will be able to tell that your CLASSPATH is set incorrectly if the AppletArchiver creates an archive file with a file size of zero bytes. There are two ways you can reset your CLASSPATH:
1. Remove the class files for the applet from the local CLASSPATH.
2. In the AppletArchiver Tool, under Options > Remote Class Loading, there is a list of strings such as "weblogic," and "tutorial". If the class name in question begins with any of these strings, the tool will obtain the class from the HTTP server, even if it also exists in the local CLASS PATH. If you add your class name to this list, all classes beginning with that name will be forced to load remotely. There is more information below.
Start the AppletArchiver. Either run it from the command line with this command:
```
 $ java utils.applet.archiver.AppletArchiver
```
(There is a syntax and usage summary in Using the WebLogic utilities.)
Or, if you installed WebLogic with the .exe version (the InstallShield version for Windows NT), find the Utilities folder in the WebLogic WebLogic folder of the Start menu; the select the AppletArchiver from the Utilities folder to run it.

Finding the Utilities folder from the Windows Start menu
In the AppletArchiver window, enter the URL for the applet.
In the AppletArchiver window, enter the name for the archive file you will create.
Click a check box to select the type of archive you want to create, either .jar or .cab file format. Note: The option to create a file in .cab format will only be displayed if you are running AppletArchiver on Windows95/NT.
Unclick the "Compress.jar" check box if you do not want to compress the .jar file. For Netscape Navigator 3.x the .jar files must be uncompressed; for Netscape Navigator 4.x archive files may be compressed. Files in .cab format are always compressed.

The AppletArchiver
From the Options menu, select "Remote class-loading list."
Use this list to specify the package names of classes that, if your applet uses, you want to force to be loaded from the applet host, rather than from your local CLASSPATH. If your applet uses the same packages that you have been developing with on your local machine, selecting those package names will make sure that all of the classes needed for your applet are loaded from the applet host, which is necessary to create the full archive to support your applet. You should also force remote loading for any classes that the browser generally will not have locally (for example, all classes that aren't java.* or sun.*).
You can force certain classes to be loaded remotely in the tool even if they are in your local CLASSPATH. In the main window for the Archiver, select the Remote class-loading list from the Options menu. Any class that starts with a string on the list in the resulting dialog box will be loaded from the codebase (the classes must of course be on the HTTP server).

List of packages to force-load from the applet host

To add to this list, type a package name in the text box and clicking "Add." To delete a package name, select the name from the list and click "Delete." Click "OK" to accept the list of packages and put away the window.
Click the "Get it" button to open and run your applet in a separate window.
Completely exercise all of the applet's features, so all of the classes, images, audio clips, and other "resource" files are downloaded and included in the archive file.
Note: The AppletArchiver's classloader will load and store the classes for all of the applets with the same URL or codebase. If you have more than one applet on an HTML page, you may accidentally create an archive file for more than one applet.
From the Options menu in the applet window, select Show tag.
This will open another window displaying all of the attributes of the applet. These attributes are taken from the APPLET tag on the HTML page with which you loaded the applet. To close this window, click the close-box in the upper left-hand corner.

Applet

AppletArchiver, with applet running
and Attributes window displayed

To close the window and save your archive, select "Quit and Save" from the Options menu. (Approximate file size will be indicated in the AppletArchiver message area.)
Place the .jar/.cab archive in your webserver's document root or WebLogic's documentRoot. The archive should be located in the directory that maps to the CODEBASE you set in your APPLET tag.
Edit the HTML file that loads your applet to add the ARCHIVE attribute to the APPLET tag and copy it into your webserver's document root or WebLogic's documentRoot. (IE browsers do not use the standard ARCHIVE attribute, but rather set an applet PARAM tag, as shown below.)
For example, this is how you might set up an applet called myapplet:
Add the following <APPLET> tag to an HTML file (e.g. "myapplet.html") to include the applet:
```
<APPLET CODEBASE="/classes/"
        CODE="examples.applets.myapplet"
        ARCHIVE="foo.jar"
        WIDTH=400
        HEIGHT=400>
</applet>
```
If you need help setting the CODEBASE and CODE for your applet, check the Tech Tip, Troubleshooting CODEBASE.
Test your applet from a remote machine, or a shell where you have set the system CLASSPATH to be empty. This will guarantee that the browser or appletviewer will load the applet classes via the server, and not the local machine. The URL we used to access the applet described in the last step was:
```
http://WebLogicURL:WebLogicPort/classes/myapplet.html
```
where WebLogicURL and WebLogicPort are the WebLogic Server host URL and the port at which WebLogic is listening for login requests.

Examples

Here is are some examples of APPLET tags that reference archives. For Appletviewer, Netscape Navigator, or HotJava viewers, the APPLET tag use the standard ARCHIVE attribute to reference an archive, as shown here:

<APPLET CODEBASE="/classes/"
      CODE="examples.applet.myapplet.html"
      ARCHIVE="foo.jar"
      WIDTH=400
      HEIGHT=400>
</APPLET>

Internet Explorer uses an applet PARAM tag that refers to the archive. For Internet Explorer, the APPLET tag uses the pattern:

<APPLET CODEBASE="/classes/"
      CODE="examples.applet.myapplet.html"
      WIDTH=400
      HEIGHT=400>
<PARAM NAME=cabbase VALUE="foo.cab">
</APPLET>

To ensure that your applet is compatible with all web browsers, you can combine both types of archive syntax, and distribute your classfiles in a non-archived format. For example:

<APPLET CODEBASE="/classes/"
      CODE="examples.applet.myapplet.html"
      ARCHIVE="foo.jar"
      WIDTH=400
      HEIGHT=400> 
<PARAM NAME=cabbase VALUE="foo.cab">
</APPLET>

For more information, check these related topics:

Change history

Release 3.1: Fixed a problem with the Applet Archiver tool that caused it to miss some applet tags.