Developer Tips - Web Start Client


This section provides developer tips related to the Java Web Start client.


General Tips

  1. Throwing of AccessControlException in the Web Start Log console when trying to connect with host name as "localhost".

  2. Enabling of the Web Start console

  3. Storing of the downloaded jar files of the client application, in the local machine.

  4. Customizing the Java Client application icon, title, description, homepage etc., displayed in the Web Start Application Manager

  5. Invoking an URL in the browser (in the Web start mode) programatically.

  6. Opening and saving a file in the Web Start Client

  7. Workaround to be done for launching Web Start Client in Netscape 6.2 and Mozilla, Konqueror and Opera browsers

  8. When does JNLP file corruption take place throwing a NullPointerException while trying to access "Java Web Start" through the browser?

  9. What is specific function of the JnlpFileUpdater?

  10. Updating hostname and port is valid when the Web Start client is connected for the first time, then why is it updated every time?

  11. How to integrate a new class file in Web Start client?

Troubleshooting Tips

  1. Throwing of the AccessControlException in the Web Start Log console after downloaded the jar files from one machine and tried to connect to another machine.

  2. Throwing of the java.lang.NoClassDefFoundError javax/jnlp/UnavailableServiceException


General Tips







Note: While specifying the user jar files in clientparameters.conf file, it should not be specified as a first entry, since in java web start, the file jar file should contain the main method. Our NmsClientClasses.jar file contains that main method, which invokes the Client Authentication Dialog.

    1. Connect web start client.

      If you do not want to regenerate the WebNMS.jnlp, when the web start button is clicked then change the <Web NMS_Home>/jsp/WebStart.jsp as per your need. In the WebStart.jsp file, follow the below given code snippet,

String webstart = request.getParameter("webstart");

if(webstart != null)




JnlpFileUpdater parser = new




else if(webstart.equals("notinstalled"))







comment or remove the line "JnlpFileUpdater parser = new JnlpFileUpdater(null);"

and compile the jsp file using <Web NMS Home>/bin/compileJSP.bat / sh file.



Trouble Shooting Tips


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