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Multi-Version Support

Java Rich Internet Applications Guide > Enhancements and Other Features > Protocol Support

The following topics are covered:

Unique MIME Type
Unique Java Plug-in Registry Key
Unique Java Plug-in Property File
Unique Java Plug-in Trace and Log Files
Unique Java Control Panel
Unique Registry Keys for JRE/JDK
Multi-version Support in Browser Sessions

Unique MIME Type

There is a unique MIME type for every new or patch version of Java Plug-in. MIME type identifies the type or version of the Java executable to be loaded and initialized by Java Plug-in. It is specified with the element type in the embed tag with Firefox and with <param name="type"> in the object tag for Internet Explorer. If you want to use a minimum version of Java Plug-in with Firefox, specify the unique MIME type in the embed tag.

The MIME type corresponding to the version of Java Plug-in installed in your computer looks like the following:

application/x-java-applet;jpi-version=<version>

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

The Java Plug-in supports supports the latest MIME type version (corresponding to the version of the Java Plug-in) and all previous MIME type versions.

Other MIME types supported by the Java Plug-in look like the following:

application/x-java-applet;version=<version>

To determine which MIME types are supported by the version of the Java Plug-in installed on your computer, enter about:plugins in the Firefox location bar. This displays a list of installed and detected plugins. Look for the Java Plug-in entry; it will list all supported MIME types. See about:plugins in the MozillaZine Knowledge Base for more information.

Example:

For Java Plug-in 1.7.0, the unique MIME type would be:

application/x-java-applet;jpi-version=1.7

Note: If you have different versions of the JRE installed, only the latest version of the Java Plug-in will be installed. As mentioned previously, this version of the Java Plug-in supports all previous versions of the Java Plug-in MIME type. These MIME types are supported by the file npjp2.dll. The location of this file is listed in the about:plugins page.

Unique Java Plug-in Registry Key

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

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

Note: If you installed a 32-bit JRE in a 64-bit operating system, then the Java Plug-in registry key is HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\JavaSoft\Java Plug-in\<version number>.

To determine <version number>, refer to the Java Plug-in entry in the Firefox about:plugins page.

Example:

For the Java Plug-in that comes with JRE 7u3, you will find the following in your registry:

HKEY_LOCAL_MACHINE\Software\JavaSoft\Java Plug-in\10.3.0

Unique Java Plug-in Property File

The property file is named deployment.properties. It is located in the following directory:

<User Application Data Folder>\Sun\Java\Deployment

where <User Application Data Folder> is an application data folder specific to the user.

As an example, for a user testuser on a Windows 7 system, the value of <User Application Data Folder> would be C:\Users\testuser\AppData\LocalLow

The value of <User Application Data Folder> is obtained from the Win32 API function call SHGetFolderPath() with CSIDL_APPDATA.

Unique Java Plug-in Trace and Log Files

The default location for trace and log files is <User Application Data Folder>\Sun\Java\Deployment\log

where <User Application Data Folder> is as defined in Unique Java Plug-in Property File.

The property javaplugin.outputfiles.path can be used to override the default location for the trace and log files. See Tracing and Logging for more information.

Unique Java Control Panel

There is a unique Java Control Panel for every new or patch release. The filename for the Java Control Panel is javacpl.exe, which is located in the directory <JRE installation directory>\bin.

Only the latest installed version of the Java Control Panel is available from the Windows Control Panel.

Unique Registry Keys for JRE/JDK

There are unique registry keys for every new or patch release of the JRE/JDK. 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; for example: 1.7.0.

Note: If you installed a 32-bit JRE in a 64-bit operating system, then the registry keys are located in Java Plug-in registry key is HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\JavaSoft.

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

Multi Version Support in Browser Sessions

Multiple JRE versions can be installed on the Windows platform. With multiple JRE's applets using MIME type jpi-version will work with Firefox browsers only if you enable the following options:

To enable the Mozilla Family option for JRE 6 and later, open Java Control Panel and click Advanced > Default Java for browsers > Mozilla family.
To enable the Mozilla and Netscape option for JRE 1.5.0 or earlier, open Java Control Panel and click Advanced > <Applet> tag support > Mozilla and Netscape.

To invoke Java Control Panel for a specific version of the JRE browse to the <JRE_HOME>/bin directory of that version and run javacpl.exe.

Note: Multiple versions of the JRE can be run in different browser sessions. However, multiple versions cannot be run in the same browser session. Should this be attempted, the user is warned and the attempt will fail.