"The fundamental goal of any given Simple Object Access Protocol (SOAP) processing framework is to deliver an incoming SOAP message to the target application. However, if we consider today's Web Services or any other application, just delivering the message to the application is not sufficient. We need to provide quality of service, such as reliability and security. To provide these features, most SOAP processing frameworks have the concept of pipes, where, any incoming or outgoing message goes through the pipe, and the pipe gets divided into smaller pieces. Each piece is known as an interceptor. 'Handler' is the Apache terminology for 'message interceptor.' In this article by Deepal Jayasinghe, we will see how to write a simple handler, what is a Phase, different types of Phase, and invalid Phase rules..."
