A Techno Blog, mainly about Java

setting websphere studio 5 runtime path


RTPWUG presentation on topic

Visibility defines which classes are "reachable" Normally, visibility extends "up" but not "down"

J2EE Java Classloader  (classpath environment variable)
Websphere Extension Classloader (ws.ext.dir for use by any application)
EAR Classloader
WAR Classloader (module classloader)
Delegation defines the "preference" order of classloaders
Parent First - "down"
Parent Last - "up" 

WebSphere uses several classloaders to load the application code from the modules deployed to the server. The number and function of these classloaders depends on the classloader isolation mode.

Do use the new J2EE application visibility provided in WebSphere 4.03, as it conforms to the J2EE 1.3 specification, and is therefore the least likely to change in the future. = true

New J2EE Application visibility – PARENT_FIRST : the .war module classloaders delegate to the parent classloader before attempting to load classes. You can change this behavior by setting the JVM system property:

New J2EE Application visibility – a separate classloader for each Web module. Classes in one Web module cannot reference classes in other Web modules .Web modules can reference classes in any utility JAR files and EJB modules.

New J2EE Application visibilitya single shared classloader for dependencies (manifest classpath entries),  utility  JAR files and EJB modules. EJB modules can reference classes in all utility JAR files, but cannot reference classes in Web modules.

The main difference between Application visibility and new J2EE Application visibility is that Application visibility lets classes in EJB modules reference classes in Web modules, and classes in   one Web module reference classes in another Web module. If you need to do this,   you will need to use Application visibility.

Applications classloader policy: how applications share classloadersor not – Single (shared) or multiple.

WAR classloader policy: how war files are loaded per application – Application (dictated by application classloader plicy), or Module.

Sample classloading issue with WAS5

November 23, 2004 - Posted by | SW Tools

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