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 to access an application server settings page.
-
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 application server settings page 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.
This option does not affect system applications, which remain isolated.
Each system application has its own class loader to load the EJB modules, shared libraries, and
dependency JAR files of that application.
|
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. |
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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 application server settings page, select either of the following values:
Option |
Description |
Classes loaded with parent class loader 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. Classes loaded with parent class
loader first is the default value for class loading mode.This value is also known as
parent first .
|
Classes loaded with local class loader first (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.
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On the application server settings page, click to access the Class loader page.
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On the Class loader page, click
New to access the settings page for a class loader.
-
On the class loader settings page, 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 local class loader first (parent last)
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.