ULC Applet Implementation

The ULC distribution provides support for running ULC applications in server mode. The UIEngine can be run as applet connecting back to the application servers.

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Installation Steps

The steps you need to take in order to be able to run the UI Engine as an applet are described in the Installation section under Setting up the UI Engine as an Applet

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Loading an HTML Page Containing the Applet

The ULC distribution contains a few experimental HTML pages. When such a page is loaded into a Web browser it starts the applet directly. No Web server is needed. If you look into the source of these web pages you will see the keyword codebase=... which tells the web browser where to look for the uiengine.jar. This keyword will not be found on the standard ULC applet pages since the web server will provide the uiengine.jar remotely.

The HTML pages are located in the Release\UIEngine\asApplet subdirectory. They allow you to start the Application Controller as applet in various forms: out of place, embedded, and embedded in a separate browser window.

The Java/Application/AppController/runExpert2222.bat file can be used to start the AppController.

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Launching ULC Applications using an Applet

Starting Applets via the ULC Http Server :

The ULC Http Server program provides the custom Web Server functionality necessary to generate custom web pages that allow a Web Browser to start the UI engine as an Applet and then connect to a running ULC Application. The ULC Http server comes with all the directory structure, Java files, and HTML pages required to run a set of sample ULC applications as applets. The setup also allows developers to easily modify the web pages to add their own applications and extensions.

The code size for the UI Engine as applet is less than 250KB resulting in reasonable download times even over low bandwidth connections. In order to avoid repeated connection overhead the code is packaged in a JAR file (Java Archive format).The Ulc Http Server treats html pages with the extension .uhtml in a special way. If the Http server is asked to serve one of these pages up, it searches within the page for all occurrances of $WEBHOST and replaces it with the host name of the machine it is running on. In this way we can create pages that can be used to connect to ULC servers running on the same machine as the Web server without having to explictly code the host name into each web page.

For example the web page to connect as an applet to a running ULC Application controller will contain the following Html tags.

<APPLET archive="uiengine.jar"code="com.ibm.ulc.UIApplet.UIApplet.class" width="300" height="70">
<PARAM name="url" value="ulc://$WEBHOST:2222/AppController">
<PARAM name="title" value="ULC AppController Applet">
</APPLET>

If the above tags are inserted into the file appcontroller.uhtml and served up by the UlcHttpServer then when the Web Browser receives the page it will start the UI Engine as an applet and attempt to connect to the ULC Application Controller running on the same machine as the Web server and on port 2222.

For more information (See: Using the Ulc Http Server)

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Customizing the ULC Applet Scheme

If you develop your own applications you can easily integrate them into the ULC applet scheme. All you need to do is change the HTML page containing the links to the ULC applications and add your own entries. If you want to run as an Applet you need to insert code as described above.
If you want to run as a helper application (See: UI engine as helper)

The Ulc Http Server home page which has both options is located in:

\Release\HttpServer\lib\UlcHttpServer\resources\start.html 

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Security restrictions when running as an Applet

When the UI Engine is running as an Applet the permissions of the application depend on the security manager installed for the Browser.By default file i/o, clipboard access and connecting to a host that is not the host from which the Appletwas started is not allowed.Netscape and Microsoft browsers have different mechanisms to configure the security manager of the Appletplease read the online help supplied with these browsers for more details.

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