Use installed optional packages

We can associate one or more shared libraries with an application using an installed optional package that declares the shared libraries in the application's manifest file. Classes represented by the shared libraries are then loaded in the application's class loader, making the classes available to the application.

 

Before you begin

Read about installed optional packages in Installed optional packages and in section 8.2 of the J2EE specification, V1.4 at http://java.sun.com/j2ee/j2ee-1_4-fr-spec.pdf.

WebSphere Application Server does not support the Java 2 Platform Standard Edition (J2SE) Installed Optional Package semantics used in the J2SE specification (http://java.sun.com/j2se/1.3/docs/guide/extensions/spec.html), which primarily serve the applet environment. WebSphere Application Server ignores applet-specific tags within manifest files.

 

Overview

Installed optional packages expand the existing shared library capabilities of an application server. Prior to V6, an administrator was required to associate a shared library to an application or server. Installed optional packages enable an administrator to declare a dependency in an application's manifest file to a shared library, with installed optional package elements listed in the manifest file, and automatically associate the application to the shared library. During application installation, the shared library .jar file is added to the class path of the application class loader.

If you use an installed optional package to associate a shared library with an application, do not associate the same shared library with an application class loader or a server class loader using the administrative console.

 

Procedure

1. Assemble the library file, including the manifest information that identifies it as an extension. Two sample manifest files follow. The first sample manifest file has application app1.ear refer to a single shared library file util.jar

   app1.ear:
       META-INF/application.xml
       ejb1.jar:
            META-INF/MANIFEST.MF:
                Extension-List: util
                util-Extension-Name: com/example/util
                util-Specification-Version: 1.4
            META-INF/ejb-jar.xml
   
   util.jar:
       META-INF/MANIFEST.MF:
           Extension-Name: com/example/util
           Specification-Title: example.com's util package
           Specification-Version: 1.4
           Specification-Vendor: example.com
           Implementation-Version: build96
   
   

   The second sample manifest file has application app1.ear refer to multiple shared library .jar files

   app1.ear:
       META-INF/application.xml
       ejb1.jar:
            META-INF/MANIFEST.MF:
                Extension-List: util1 util2 util3
                Util1-Extension-Name: com/example/util1
                Util1-Specification-Version: 1.4
                Util2-Extension-Name: com/example/util2
                Util2-Specification-Version: 1.4
                Util3-Extension-Name: com/example/util3
                Util3-Specification-Version: 1.4
            META-INF/ejb-jar.xml
   
   util1.jar:
       META-INF/MANIFEST.MF:
           Extension-Name: com/example/util1
           Specification-Title: example.com's util package
           Specification-Version: 1.4
           Specification-Vendor: example.com
           Implementation-Version: build96
   
   util2.jar:
       META-INF/MANIFEST.MF:
           Extension-Name: com/example/util2
           Specification-Title: example.com's util package
           Specification-Version: 1.4
           Specification-Vendor: example.com
           Implementation-Version: build96
   
   util3.jar:
       META-INF/MANIFEST.MF:
           Extension-Name: com/example/util3
           Specification-Title: example.com's util package
           Specification-Version: 1.4
           Specification-Vendor: example.com
           Implementation-Version: build96
   
   

2. Create a shared library that represents the library file assembled in step 1. This installs the library file as a WAS shared library.

3. Copy the shared library .jar file to the cluster members.

4. Assemble the application, declaring in the application manifest file dependencies to the library files named the manifest created for step 1.

5. Install the application on the server or cluster.

 

Result

During application installation, the shared library .jar files are added to the class path of the application class loader.

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See Also

Class loaders
Shared library files

 

Related Tasks

Manage shared libraries

 

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