Applet served by Java Web Start, resources requested to WEB Server before look in the JAR files

Question

I am new here and I apologize for my bad English.

I have a little problem with an Applet class served by Java Web Start technology. I have some platform dependent JAR files which Web Start download correctly, but when I get the content by getResourceAsStream(String fileName) method of ClassLoader object, first is made a GET request of fileName to WEB Server, after received a 404 Not Found response, the resource is loaded correctly from JAR file. The problem is that I have many files inside the JAR, so I have a lot of unnecessary load on the WEB Server and consequently I have to wait for long time before I can use the Applet.

Searching on Google I have found some discussions where it was said to add the parameter codebase_lookup with value false, but this has not solved the problem. This page, in relation to the codebase_lookup parameter, says that the default behavior of an Applet is to load resources from JAR file and then from the Applet codebase, in my case the behavior is the opposite.

I also added the eager="true" attribute for each JAR resource in the .jnlp file, but the behavior is always the same. The Applet was developed and built with NetBeans, the html and jnlp files generated are the following.

launch.html

<applet width="300" height="300">
        <param name="jnlp_href" value="launch.jnlp"/>
        <param name="codebase_lookup" value="false"/>
</applet>

launch.jnlp

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<jnlp codebase="http://192.168.23.4/contact" href="launch.jnlp" spec="1.0+">
<information>
    <title>ContactNR</title>
    <vendor>Roberto Santini</vendor>
    <homepage href=""/>
    <description>ContactNR</description>
    <description kind="short">ContactNR</description>
</information>
<resources>
<j2se version="1.5+"/>
<jar eager="true" href="ContactNR.jar" main="true"/>
<jar eager="true" href="lib/VDK.jar"/>
<security>
    <all-permissions/>
</security>
</resources>
<resources arch="amd64" os="Linux">
    <jar eager="true" href="lib/liblinux64.jar"/>
</resources>
<resources arch="x86_64" os="Linux">
    <jar eager="true" href="lib/liblinux64.jar"/>
</resources>
<resources arch="x86" os="Linux">
    <jar eager="true" href="lib/liblinux.jar"/>
</resources>
<resources arch="i386" os="Linux">
    <jar eager="true" href="lib/liblinux.jar"/>
</resources>
<resources os="Windows">
    <jar eager="true" href="lib/libwin.jar"/>
</resources>
<resources os="MacOs">
    <jar eager="true" href="lib/libmac.jar"/>
</resources>
<applet-desc height="300" main-class="com.netresults.voip.ContactNR" name="ContactNR" width="300">
    <param name="codebase_lookup" value="false"/>
</applet-desc>
</jnlp>

Can someone help me? Thanks at all,

Roberto.

Answer 1

I solved this problem by adding an index to the JAR-file. After building your jar, run the command:

JAR -i <path/to/jar-file>

It has to be run as a separate step from the actual JAR-ing.

Explanation: When the startup-process encounters an INDEX.LIST in META-INF, it trusts this, and will not go looking for the files on the server.