Day 20. Using RPC-Style Web Services with J2EE

So far, you have seen how to use existing J2EE technologies to build multitier applications. However, the world moves on. A key area of interest at the turn of the millennium is how to integrate applications both within and between organizations. Web Services provide a flexible and powerful integration mechanism that can be used to expose existing functionality and components to other organizations or to new applications. Today and tomorrow, you will see how you can use Web Services to build bridges between J2EE application components and any other platforms that support Web Services.

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 will

• Examine the concepts underlying Web Services and how Web Services fit with J2EE

• Create a client for an RPC-style Web Service

• Implement an RPC-style Web Service

• Generate client code from Web Services Description Language (WSDL) documents and generate WSDL documents from your server implementations

• Pass complex Java types between client and service

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

The aim of the last two days is to describe how to use J2EE technologies to implement and access a Web Service. This chapter will give an overview of the Web Service architecture and show how to generate and consume SOAP messages based on a WSDL interface.