Does ta java client always need all the jars of the jboss "client" folder? If not how can I determine which jars the client need?
No. Several of the packages contain subsets of the same classes, to suit different client uses. Normally, you can get your functionality with jbossall-client.jar. Occassionally, dependent on use, you may need to supplement it with log4j or some of the other non-JBoss JARs. However, this is rare.