Solutions in this chapter:

• Understanding SOAP

• SOAPElement and JAXM DOM

• JAXM SOAP Elements

• Creating a SOAP Message

• Bringing it all Together A Complete SOAP Client

Introduction

For the next few chapters, we will explore the development of SOAP communications using the Java Web Services Developers Pack. This chapter will provide a brief introduction to SOAP, which is an XML-based protocol for communicating between distributed systems and can be extended with attachments containing essentially any media type.

The Java API for XML Messaging (JAXM) provides an API and specification for supporting services that enable developers to implement SOAP communications in Java. This chapter will cover the implementation of SOAP clients using JAXM (that is, consumers of web services), and the next chapter will cover the implementation of SOAP servers (that is, providers of web services).

Unlike most of the scenarios covered in this book, it is possible to implement synchronous communications (that is, request/reply) without the aid of a servlet or EJB container, and this chapter will fully describe an example of such a standalone Java application that functions as a SOAP client.

Understanding SOAP

The Simple Object Access Protocol (SOAP) is an XML-based protocol that is designed to be a lightweight method for exchanging information between distributed systems. It is very much a cross-platform and cross-vendor technology, and has the backing of a very wide range of companies. We will discuss two flavors of SOAP documents: plain SOAP, which is a pure XML message, and SOAP with Attachments, which allows for...