Thanks Mark for answering my query. Now I have set all the jars file in the classpath, but still m getting the same exception. The exception is caused by : Null pointer exception. I am not able to understand why it is giving me this exception, while in the mailing list I didn't found anybody having this problem. This is my code snippet : KnowledgeBuilderConfiguration config = KnowledgeBuilderFactory. newKnowledgeBuilderConfiguration(); config.setProperty("drools.dialect.java.compiler", "ECLIPSE"); KnowledgeBuilder kbuilder =KnowledgeBuilderFactory.newKnowledgeBuilder( config ); //KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); kbuilder.add(ResourceFactory.newClassPathResource( "shopingdiscount.drl"), ResourceType.DRL); Am I missing anything that is to initialized , so that I can get through this Null Pointer Exception. Please help me to through of this situation. I am stuck in this. Thanks & Regards Pardeep Ruhil ______________________________________________________________________