This article describes Java™ API for XML-Based RPC (JAX-RPC) handlers and demonstrates how to easily generate, implement and add a JAX-RPC handler to an existing WebSphere Web service imported from the IBM® Rational® Application Developer Samples Gallery. Handlers are pluggable applications for handling XML messages and can be registered to run before or after the Web service or Web service client is invoked. They are frequently used in common functions such as processing message headers, logging activity, and measuring performance. This article shows you how to implement and deploy a message logging handler.