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Java architecture for XML binding: efficient mapping between Java and XML documents. (First Look).

Article Excerpt
Two foundation technologies, Java and XML, represent the marriage of portable code and data. A key ingredient of a successful marriage is compatibility. XML and a number of XML-based vocabularies are being used extensively as the standard data-exchange mechanism (and beyond) by both stand-alone Java 2, Standard Edition (J2SE) applications and server-based Java 2, Enterprise Edition (J2EE) enterprise applications.

A basic requirement in a number of these programmatic scenarios is the mapping of XML data as Java objects and/or vice versa (convening Java objects into XML). Although there exists a core set of APIs for processing XML, particularly the Java API for XML Processing, which includes basic DOM/SAX-based XML parsing capabilities, object-oriented Java programmers have always needed to consume, manipulate, and generate XML in a more object-oriented fashion through a standardized API set and utilities. The requirement is similar to those presented in scenarios where relational data must be mixed with Java objects, which has resulted in a number of object-relational mapping mechanisms.

Also highlighting the need for an efficient XML binding mechanism are the two extremely different mechanisms that SAX and DOM present for efficiently processing XML. Whereas SAX (Simple API for XML) represents a very efficient, albeit low-level, event-based XML processing engine, DOM (Document Object Model) provides a much easier generic in-memory, tree-based navigation structure. In a nutshell, choosing DOM over SAX may result in significant memory impact, and choosing SAX may present significant programmatic complexity.

JAXB

Java Architecture for XML Binding (JAXB, also known as Project Adelard by Java developers who have been following this project for some time) provides an efficient bidirectional mapping between Java objects and XML documents. Compared to SAX, JAXB provides ease of programming, utilizing a standardized Java objects-based binding framework and a set of tools that can convert existing XML Schemas to JAXB binding classes. However, JAXB-generated Java...