You 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.
Before you begin
This topic assumes that an administrator created an application server
on a WebSphere Application Server product.
About this task
Configure the class loaders of an application server to set class-loader
policy and mode values which affect all applications that are deployed on
the server. Use the administrative console to configure the class loaders.
Procedure
- Click Servers > Application Servers > server_name to
access the settings page for
an application server.
- Specify the application class-loader policy for the application
server.
The application class-loader policy controls the isolation
of applications that run in the system (on the server). An application class
loader groups enterprise bean (EJB) modules, shared libraries, resource adapter
archives (RAR files), and dependency Java archive (JAR) files associated to
an application. Dependency JAR files are JAR files that contain code which
can be used by both enterprise beans and servlets. The application class-loader
policy controls whether an application class loader can be shared by multiple
applications or is unique for each application.
Use the settings page for the application server to specify
the application class-loader policy for the server:
Option |
Description |
Single |
Applications are not isolated from
each other. Uses a single application class loader to load all of the EJB
modules, shared libraries, and dependency JAR files in the system. |
Multiple |
Applications are isolated from
each other. Gives each application its own class loader to load the EJB modules,
shared libraries, and dependency JAR files of that application. |
- Specify the application class-loader mode for the application server.
The application class loading mode specifies the class-loader mode
when the application class-loader policy is Single.
On the settings page for the application
server, select either of the following values:
Option |
Description |
Parent first |
Causes the class loader to
delegate the loading of classes to its parent class loader before attempting
to load the class from its local class path. Parent first is the
default value for class loading mode. |
Parent last |
Causes the class loader to
attempt to load classes from its local class path before delegating the class
loading to its parent. Using this policy, an application class loader can
override and provide its own version of a class that exists in the parent
class loader. |
- Specify the class-loader mode for the class loader.
- On the settings
page for the application server, click Java and Process Management
> Class loader to access the Class loader page.
- On the Class
loader page, click New to access the settings page for a class
loader.
- On the settings page for a class loader, specify the class
loader order. The Classes loaded with parent class loader
first value causes the class loader to delegate the loading of classes
to its parent class loader before attempting to load the class from its local
class path. The Classes loaded with application class loader
first value causes the class loader to attempt to load classes from its
local class path before delegating the class loading to its parent.
- Click OK.
An identifier is assigned to a class-loader instance. The instance
is added to the collection of class loaders shown on the Class loader page.
What to do next
Save the changes to the administrative configuration.