Download correct JRE before launching the jnlp application

Question

Hi,
I have this requirement that before launching the jnlp application, the code should check the version of JRE installed on client's system, if it is less than 1.6 u10 then install the latest available JRE before launching the application.
I am using the Java Script in my jsp to achieve this objective and it is working fine with non-IE web browsers. The trouble starts when the client machine is using 1.6.0_6 jre, in that case IE is not able to download /redirect user to the sun's page for the download of latest JRE.
My java script code as follows:
<script language="JavaScript">
var launch = null;
// try to check the JRE version installed on client's machine.
//if its less than 1.6.10 redirect to Sun Micro systems website.
//and then after installation, launch Receptionst and Call Center application
function checkForInstalledJreVersionAndLaunch(appName)
     //detect browser used at client's machine
     var windowsIE = (navigator.userAgent.indexOf('MSIE') != -1) && (navigator.userAgent.indexOf('Win') != -1);
     if (windowsIE) {
          alert(windowsIE);
         document.write("<OBJECT codeBase=\"http://java.sun.com/update/1.6.0/jinstall-6u10-windows-i586.cab#Version=6,0,10,0\" classid=\"clsid:5852F5ED-8BF4-11D4-A245-0080C6F74284\" height=0 width=0>");
         document.write("<PARAM name=app VALUE=\"http://localhost:8080/"+appName+"/launch.jnlp\">");
          document.write("<PARAM NAME=back VALUE=true>");
          document.write("</OBJECT>");
     }else{
          if (navigator.mimeTypes && navigator.mimeTypes.length)
               if(!checkWebStartWersion())
                    window.open("http://jdl.sun.com/webapps/getjava/BrowserRedirect?locale=en&host=java.com","needdownload");
               launch = setInterval('launchJNLP("http://localhost:8080/'+appName+'/launch.jnlp")',100);
function launchJNLP(app) {
    if (checkWebStartWersion()) {
        clearInterval(launch);
        window.location = app;
function checkWebStartWersion()
     var isMajorVersion = false;
     var isMinorVersion = false;
     navigator.plugins.refresh(true);
     if(navigator.mimeTypes['application/x-java-jnlp-file'])
          for(var i=0;i <navigator.mimeTypes.length; i++)
               var pluginType = navigator.mimeTypes.type;
               if(pluginType.indexOf("x-java-applet;jpi-version") > -1)
                    var jreVersion = pluginType.substring(pluginType.indexOf("_")+1,pluginType.length);
                    var jreUpdateNumber = parseInt(jreVersion);
                    if(jreUpdateNumber >= 10)
                         isMinorVersion = true;
               if(pluginType.indexOf("x-java-applet;version") > -1)
                    var jreVersion = pluginType.substring(pluginType.indexOf(".")+1,pluginType.length);
                    var jreUpdateNumber = parseInt(jreVersion);
                    if(jreUpdateNumber >=6)
                         isMajorVersion = true;
     return (isMajorVersion && isMinorVersion);
function launchApplication()
     checkForInstalledJreVersionAndLaunch("appname");
</script>

Answer 1

I hear your frustration. I am attempting to do something similar.
To me, it looks like this ActiveX control has no ability to detect a minor version of JRE. It knows if some JRE 1.6 is installed or not, but not if say JRE 1.6.0_10 or higher is installed. But, if it finds that some JRE less than 1.6 is installed such as a 1.5 version, this ActiveX control can automatically install the latest JRE 1.6.0_12. This seems to work well for me. But, the overall behavior is not consistent. It looks to me that this ActiveX control is only good for making sure that the client has some version of JRE 1.6. It doesn't care which one.
A similar issue exists if you try to use Java WebStart to automatically download the correct JRE 1.6 version.
<j2se version="1.6+" href="http://java.sun.com/products/autodl/j2se" />As of today, this code will tell Java WebStart that it needs some version of JRE 1.6 or higher to run your app. If the client does not have it, Java WebStart will download and install 1.6.0_07. Apparently, WebStart thinks that version is a "good" one - whatever that means.
If instead you use this in your .jnlp file:
<j2se version="1.6.0_10+" href="http://java.sun.com/products/autodl/j2se" />Java WebStart will not run your application unless the client has at least 1.6.0_10 installed. However, it is not able to install this version if the client does not have at least 1.6.0_10 already installed. It isn't smart enough for that. It looks like no one at sun has gotten around to updating http://java.sun.com/products/autodl/j2se to deal with recent JREs.
Maybe I'm missing something, but WebStart deployment is more difficult than it needs to be. Sun introduces all sorts of new things into minor versions of Java, but nobody seems to be interested in making sure that the end user can have seemless upgrade experience.
And people wonder why Flash and AJAX have become so popular...
There probably is another workaround using a Java applet to determine what version is really installed before launching WebStart, but it just seems like an ugly hack to me. If an older version of Java 1.6 is detected, you could direct the user to java.sun.com in a new browser window, just as in the case of Firefox in your code. Ugly, but it would probably work.