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SOAP, messages with attachments.

Article Excerpt
Organizations are being challenged to partner with other organizations in order to respond more rapidly to new business opportunities, increase the efficiency of business processes, and reduce the time-to-market for their products. To address these issues, they're typically required to develop interoperability between disparate legacy applications to support collaborative business processes.

This is accomplished by coordinating the exchange of business documents between applications in a predefined manner. For example, two insurance companies with different systems may need to exchange auto insurance claim data, such as a TIFF file for claims processing.

Enterprise applications that support these types of requirements are known as business services. Supporting business services through Web applications, commonly known as Web services, requires a careful evaluation of available technologies. An important underlying technology of Web services is Simple Object Access Protocol. SOAP enables applications to communicate with each other in a platform, language, and operating system-independent manner.

For those who need to use a Web service to perform a functionality such as sending a document in the form of attachments (e.g., a TIFF file) from one application to another using SOAP, a pertinent specification is the SOAP Messages with Attachments note. This article discusses this emerging W3C note and illustrates how it can be used with the Apache SOAP implementation.

SOAP Messages with Attachments Specification

As you know, SOAP is a simple, lightweight XML-based distributed computing protocol. The SOAP 1.1 specification essentially comprises three parts:

1. A framework for describing the contents of a SOAP message and how it's processed

2. An encoding standard for objects sent over SOAP

3. A mechanism for representing remote procedure calls (RPC) using SOAP.

A SOAP message is an XML document that comprises a SOAP envelope. Within the envelope is an optional SOAP header and a mandatory SOAP body. The SOAP message header represents the metadata of the message and provides a way to extend SOAP. The SOAP message body is the actual message payload. The details of a remote procedure call including the arguments are described in the envelope that is transported from one application to another over a selected protocol (e.g., HTTP). HTTP provides a firewall-friendly application-level protocol for communication between heterogeneous applications. The SOAP Messages with Attachments specification builds on SOAP 1.1.

Before we discuss this specification,...