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Thread: noClassDefFoundError trying to run JNLP file with Web Start

  1. #1
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    Sep 2011
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    Default noClassDefFoundError trying to run JNLP file with Web Start

    I am attempting to run a swing application on my site; I created the jar with my class file as its sole member, and wrote the JNLP file below. But when I try to run the JNLP with Web Start either from the browser or my desktop, I keep getting this error which I've shown under the JNLP code. I am new at this so can anyone tell if I am making any obvious errors?

    <?xml version="1.0" encoding="utf-8"?>
    <!- JNLP File for the PageData Application ->
    		<title>PageData Application</title>
    		<homepage href="----------------"/>
    		<icon href="pagedataicon.gif"/>
    		<j2se version="1.7"/>
    		<jar href="PageData.jar" main="true"/>
    	<application-desc main-class="PageData"/>

    java.lang.NoClassDefFoundError: PageData (wrong name: PageData/PageData)
    	at java.lang.ClassLoader.defineClass1(Native Method)
    	at java.lang.ClassLoader.defineClass(Unknown Source)
    	at java.security.SecureClassLoader.defineClass(Unknown Source)
    	at java.net.URLClassLoader.defineClass(Unknown Source)
    	at java.net.URLClassLoader.access$100(Unknown Source)
    	at java.net.URLClassLoader$1.run(Unknown Source)
    	at java.net.URLClassLoader$1.run(Unknown Source)
    	at java.security.AccessController.doPrivileged(Native Method)
    	at java.net.URLClassLoader.findClass(Unknown Source)
    	at com.sun.jnlp.JNLPClassLoader.findClass(Unknown Source)
    	at java.lang.ClassLoader.loadClass(Unknown Source)
    	at java.lang.ClassLoader.loadClass(Unknown Source)
    	at com.sun.javaws.Launcher.doLaunchApp(Unknown Source)
    	at com.sun.javaws.Launcher.run(Unknown Source)
    	at java.lang.Thread.run(Unknown Source)

  2. #2
    Junior Member
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    Sep 2011
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    Default Re: noClassDefFoundError trying to run JNLP file with Web Start

    Finally got it working, just thought I'd update this post with my solution in case it can help anyone else with the same problem. I'm not even sure why it works, but this is what I did: In my first post, I had created the JAR from the command line with the class file as its only member. I tried a few more times using Eclipse 1.4 instead, and in generating the JAR file it didn't work with my JNLP until I specified the main class in the field titled "select the class of the application entry point" on the "Manifest Specification" section of options. Once I did this, I updated my JNLP file to reflect the new path of the main class (now it's PageData.PageData) since my JAR file was now the entire project instead of just the class file. Then I signed my JAR and it ran fine once I uploaded it to my server. Again, not sure why this works because I don't really understand what specifying the main class in the JAR manifest even does, or what a manifest even is. Could anyone explain?
    Last edited by sonicjr; October 13th, 2012 at 02:02 AM.

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