Class loading
Class loaders are part of the 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 runtime behavior of packaged applications of deployed applications.
This topic 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 topic 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 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.
- 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 JAR file names. All JAR files in the specified directory are added into the class path of the WAS extensions class loader. If a resource driver requires a native library (.dll or .so file), specify the name of the directory containing the library in the native path of the resource configuration.
- Specify class-loader values for an application server.
- Specify class-loader values for an installed enterprise application.
- Specify the class-loader mode for an installed web module.
- If the deployed application uses shared library files, associate the shared library files with the application. Use a library reference to associate a shared library file with the application.
- If we have not done so already, define shared libraries for library files that the applications need.
- Define a library reference for each shared library that the application uses.
What to do next
After configuring class loaders, ensure that the application performs as desired. To diagnose and fix problems with class loaders, refer to Troubleshooting class loaders.
Subtopics
- Class loaders
Class loaders find and load 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.
- Configure class loaders of a server
We can configure the application class loaders for an application server. Class loaders enable applications that are deployed on the application server to access repositories of available classes and resources.
- Class loader collection
Use this page to manage class-loader instances on an application server. A class loader determines whether an application class loader or a parent class loader finds and loads Java class files for an application.
- Configure application class loaders
We can set values that control the class-loading behavior of an installed enterprise application. Class loaders enable an application to access repositories of available classes and resources.
- Configure web module class loaders
We can set values that control the class-loading behavior of an installed web module.
- Class loading: Resources for learning
Additional information and guidance on class loading is available on various Internet sites.
Related tasks
Create shared libraries Associate shared libraries with applications or modules Troubleshooting class loaders Assembling applications Manage shared libraries
Class loader settings Enterprise application settings Web module deployment settings Java EE client application class loading