Java Enterprise in a Nutshell, Second Edition

Chapter 9. Java and XML

The Extensible Markup Language (XML) has become an essential technology for Enterprise Applications. The XML specification^[34] allows users to define unique and structured document formats, allowing for easy and flexible data exchange between applications. Since the syntax of an XML document is bound by a public specification, XML documents can be read and manipulated by a wide variety of tools. Also, because XML documents are text-based, they can be easily transmitted between different systems using a number of transportation mechanisms, from JMS to HTTP.

XML documents can be freely structured, although they must abide by a basic set of XML rules that define a well-formed document. More commonly, however, the document structure is further defined by a Document Type Definition (DTD). With a standardized DTD, enterprise applications can exchange data without knowledge of each other’s native formats. Industry working groups have defined DTDs for everything from bank transactions to medical records to electronic books

XML is also an integral part of the emerging concept of web services. XML based messaging systems, such as the Simple Object Access Protocol (SOAP), allow web services to interact with each other across vendors, platforms, and implementations. Another XML-based standard, WSDL (the Web Services Description Language) describes web services and how to integrate with them. XML-based service registries built on Universal Description, Discovery ...