Class loading

Class loaders are part of the Java virtual machine (JVM) code and are responsible for finding and loading class files. Class loaders enable
applications that are deployed on servers to access repositories of available classes and resources. Application developers and deployers must consider the location of class and resource files, and the class loaders used to access those files, to make the files available to deployed applications. Class loaders affect the packaging of applications and the run-time behavior of packaged
applications of deployed applications.

This article describes how to configure class loaders for application files or modules that are installed on an application server.

To better understand class loaders in WebSphere Application Server, read Class loaders. The article Class loading: Resources for learning refers to additional sources.

Configure class loaders for application files or modules that are installed on an application server using the administrative console. You configure class loaders to ensure that deployed application files and modules can access the classes and resources that they need to run successfully.

1. If an installed application module uses a resource, create a resource provider that specifies the directory name of the resource drivers. Do not specify the resource Java archive (JAR) file names. All JAR files in the specified directory are added into the class path of the WebSphere Application Server extensions class loader. If a resource driver requires a native library (.DLL or .so file), specify the name of the directory that contains the library in the native path of the resource configuration.

2. Specify class-loader values for an application server.

3. Specify class-loader values for an installed enterprise application.

4. Specify the class-loader mode for an installed Web module.

5. If your deployed application uses shared library files, associate the shared library files with your application. Use a library reference to associate a shared library file with your application.

   1. If you have not done so already, define a shared library instance for each library file that your applications need. See Managing shared libraries for more information.

   2. Define a library reference instance for each shared library that your application uses. See Associating shared libraries with applications for more information.

6. Optional: Configure class preloading.

Class loader collection
Configuring application class loaders
Configuring Web module class loaders
Configuring class preloading
Class loading: Resources for learning

Related concepts
J2EE application client class loading

Related tasks
Assembling applications
Managing shared libraries

Related reference
Enterprise application settings
Web module deployment settings