Day 20. Using RPC-Style Web Services with J2EE

As you saw yesterday, there are many ways of integrating existing and third-party applications and components with J2EE applications. However, the plethora of integration mechanisms has long been an issue. It would be better if there were a more consistent way of integrating applications. Additionally, expectations have increased around the capability to integrate applications that span organizations—particularly across the common communication medium of the Internet. Web Services provide a flexible and powerful integration mechanism that can be used to expose existing functionality and components to other organizations or new applications. Today and tomorrow, you will see how you can use Web Service protocols to build bridges between J2EE application components and any other platforms, applications, or components that support those Web Service protocols.

Web Services are seen by many as the next wave of the Internet revolution. The vision is of a Web as rich with functionality as the current Web is with information. The challenge is to expose this functionality in a consistent and usable way.

Today, you learn about

• The concepts underlying Web Services and how Web Services fit with J2EE

• Implementing RPC-style Web Service clients and servers

• Exposing session EJBs as Web Services

First, you need to understand why you would use Web Services.

The aim of the last two days was to describe how to use J2EE technologies to implement and access a Web Service. This chapter will give an overview of how Web Service interactions work and will show how you can use JAX-RPC to generate and consume SOAP messages based on a WSDL interface.