Specifying Family JRE Versions for Java Applets

In the JRE 5.0 Update 7 release for Java Plug-in for Internet Explorer, two new family Class IDentifier (CLSID) fortags are introduced. You can use these tags to specify that the Java applet requires the JRE 1.4.2 or the JRE 5.0 family to run. In the JRE 6 release for Java Plug-in for Internet Explorer, a third new family CLSID is introduced so that you can specify that the Java applet requires the JRE 1.4.2, JRE 5.0, or JRE 6 family to run. In all releases, you cannot specify a specific release within a JRE family.

The following shows the family CLSID to specify for each JRE family version.

JRE Family Version 1.3.1 Note that the 1.3.1 family clsid is not currently available. It will be available in forthcoming JRE 6 and JRE 5.0 update releases.

 

Family CLSID: clsid:CAFEEFAC-0013-0001-FFFF-ABCDEFFEDCBA

 

JRE Family Version 1.4.2
Family CLSID: clsid:CAFEEFAC-0014-0002-FFFF-ABCDEFFEDCBA

JRE Family Version 5.0
Family CLSID: clsid:CAFEEFAC-0015-0000-FFFF-ABCDEFFEDCBA

JRE Family Version 6.0
Family CLSID: clsid:CAFEEFAC-0016-0000-FFFF-ABCDEFFEDCBA

JRE Family Version 7.0
Family CLSID: clsid:CAFEEFAC-0017-0000-FFFF-ABCDEFFEDCBA

When a JRE family is specified, the Java Plug-in software looks for the latest release of that family that is currently installed. The Java Plug-in software prefers a release that is equal to or later than theSECURITY baseline for that JRE family.

The security baseline consists of the version number of the latest release for each JRE family that is available when the latest JRE family is built. For example, when the JRE 5.0 Update 7 release was built, the security baseline for the 5.0 JRE family was 5.0 Update 7. For the 1.4.2 JRE family, the security baseline was 1.4.2_10. Starting with the JRE 5.0 Update 7 release, the security baseline information is included in each release of the most current JRE family.

Suppose the following applet that uses the 1.4.2 family CLSID is launched:

<OBJECT
     classid="clsid:CAFEEFAC-0014-0002-FFFF-ABCDEFFEDCBA"
     width="200" height="200">
     <PARAM name="code" value="Applet1.class">
</OBJECT>

If one or more versions of the JRE 1.4.2 release are installed and the latest version is no older than the security baseline, the Java Plug-in software runs the applet using that release.

If one or more versions of the JRE 1.4.2 release are installed and the latest version is older than the security baseline, the Java Plug-in software displays a warning.

The user must click Yes to run the applet. The user also has theOPTION of downloading the latest release.

If the JRE 1.4.2 release is not installed, the Java Plug-in softwareOFFERS to download its most recent version.

Similar actions are taken for a CLSID that specifies the JRE 5.0 family when a later JRE family is released. In this case, where JRE 5.0 is the latest family JRE, the firstACTION is taken. In some cases, you might want to detect if the family CLSID is available and then generate the

<SCRIPT language="JavaScript">

    // Return true if the family version is supported.
    function isFamilyVersionSupported() {
        try {
            return (new ActiveXObject("JavaPlugin.FamilyVersionSupport") != );
        } catch (exception) {
            return false;
        }
    }

    if (isFamilyVersionSupported()) 
        // Family CLSID is supported
        document.writeln("<OBJECT classid=\"clsid:{CAFEEFAC-0014-0002-FFFF-ABCDEFFEDCBA}\" ..... </OBJECT>");
    else  
        // No family CLSID supported, continue to use specific version
        document.writeln("<OBJECT classid=\"clsid:{CAFEEFAC-0014-0002-0008-ABCDEFFEDCBA}\" ..... </OBJECT>");
</SCRIPT>