Class Loader

Class Loader !!

Java Class Loader:

Class Loader is a process which enables the Java Virtual Machine (JVM) to load java classes.

Types of Java Class Loader:

·         Bootstrap Class Loader – responsible for loading only the core java libraries like vm.jar,core.jar etc.

·         Extension Class Loader – responsible for loading the code in the extensions directories -<JAVA_HOME>/jre/lib/ext

·         Application Class Loader – responsible for loading the code that is found on java.class.path, which ultimately maps to the system CLASSPATH variable.

WEBSPHERE CLASS LOADER:

Websphere Extensions Class Loader: The Websphere extensions class loader is where Websphere itself is loaded. In WAS6.1, Websphere runtime classes are stored in the <was_home>\plugins directory.

Application Class Loader:EJB modules, utility JARs, resource adapter files, and shared liabries associated with an application are always grouped together into same class loader which is called application class loader. Utility JARs contain code used by both EJBs and servlet. Application class loader can be share by multiple applications (EARs) and also can be unique for each application.

WAR Class Loader:

Every web module comes with their own class loader called WAR class loader which is used to load the contents of the WEB-INF/classes and WEB-INF/lib directories.

If the WAR class loader policy is set to Single class loader for application, the Web module contents are loaded by the application class loader in addition to the EJBs, RARs, utility JARs, and shared libraries