Multi-Version Support

This chapter includes the following topics:

So that multiple JRE versions may be deployed in the same environment, every new or patch release of Java Plug-in uniquely identifies registry keys, CLSID, MIME type and other resources.

Notes: (1) For an explanation of product version numbers, see the note in the section called "Using OBJECT, EMBED and APPLET Tags in Java Plug-in." In this section, a mix of version 1.3 and 1.4 examples is given. (2) While the examples below are for Windows, multi-version support also applies to Solaris and Linux.

Unique CLSID

There is a unique CLSID for every new/patch version of Java Plug-in. (CLSID is used in the OBJECT tag with Internet Explorer running on Windows.) If you want a particular version of Java Plug-in to be used, then specify this unique CLSID in the OBJECT tag. The CLSID is stored in the registry in: 


In general the CLSID looks as follows:

CAFEEFAC-<major version>-<minor version>-<patch version>-ABCDEFFEDCBA

where major version, minor version and patch version are all 4-digit hexadecimal numbers for the Java Plug-in/JRE release.


For example, the CLSID for Java Plug-in 1.4 is:


and you would find this in the registry:


The CLSID for 1.3.0_03 is:


and you would find this in the registry:


Note that CLSID is also stored in: 

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Code Store Database\Distribution Units\

Unique MIME Type and dll

There is a unique MIME type and NP*.dll for every new/patch version of Java Plug-in. (MIME type is used in the EMBED tag with Netscape and as a PARM in the OBJECT tag for Internet Explorer. NP*.dll is unique to Netscape.) If you want to use a particular version of Java Plug-in with Netscape, specify the unique MIME type in the EMBED tag.

Note that this MIME type will be supported by an NP*.dll with a unique name for every new/patch version. Thus, installing different version of Java Plug-in does not overwrite other .dll files in Navigator's Plugins directory.

In general MIME type looks like this:


where version includes the major, minor and patch version numbers.


The MIME type for the 1.4 release is:


The MIME type for the 1.3.0_03 release is:


MIME type is supported in the file

        NPJPI<modified version number>.dll


For Java Plug-in 1.4.0_01, the unique MIME type would be:


and it would be supported in the file:


in Navigator's Plugins directory.


Prior to release 1.4.0, the supporting .dll file was of the form NPJava<modified version number>.dll; e.g., release 1.3.0_03 would we supported by NPJava130_03.dll.

Unique Java Plug-in Registry Key

There is a unique Java Plug-in registry key for every new/patch version of Java Plug-in. The main Java Plug-in registry key is:

HKEY_LOCAL_MACHINE\Software\JavaSoft\Java Plug-in\<version number>

where the <version number> will include the major, minor and the patch version numbers.


For Java Plug-in 1.4 you will find the following in your registry:

HKEY_LOCAL_MACHINE\Software\JavaSoft\Java Plug-in\1.4.0

Unique Java Plug-in Property File

As in previous versions, the property file continues to be located in <user.home>\.java. However, the filename will be unique in every new/patch release and have the following form:

<user.home>\.java\properties_<modified version number>

where the <modified version number> will include the major, minor, and patch version numbers; e.g.,


Unique Java Plug-in Trace and Log Files

A trace file has been created automatically in <user.home> when Java Console is enabled. Its purpose is to capture in a single file the same messages that are displayed in Java Console. But in order to avoid conflict, this file is now uniquely named in every new/patch release. There is also a uniquely named log file. These files have the form:

<user.home>\.plugin<modified version number>.trace
<user.home>\.plugin<modified version number>.log

where the <modified version number> includes the major, minor and the patch version numbers; e.g., .plugin140_xx.trace

Unique Java Plug-in Control Panel

There is a unique file name for the Java Plug-in Control Panel dll in every new/patch release. From the Windows Control Panel, this allows the user to launch the Control Panel for a particular version of Java Plug-in. The filename for the dll is of the form:

plugincpl<modified version number>.cpl

where the <modified version number> will include the major, minor and the patch version numbers; e.g., plugincpl130_01.cpl

Note below that the user can choose which version of the Java Plug-in Control Panel to launch.

Windows Control Panel window

Unique Registry Keys for JRE/JDK

There are unique registry keys for every new/patch release of the JRE/JDK. Prior to release 1.3 of Java Plug-in, installating multiple versions of Java Plug-in overwrote the JRE/JDK registry keys. These registry keys are located as follows:

HKEY_LOCAL_MACHINE\Software\JavaSoft\Java Runtime Environment\<version number>
HKEY_LOCAL_MACHINE\Software\JavaSoft\Java Development Kit\<version number>

where the <version number> includes the major, minor and the patch version numbers; e.g., 1.3.0_01

These keys allow Java Plug-in to locate the proper version of JRE/JDK.