Transformation API For XML


This overview describes the set of APIs contained in javax.xml.transform. For the sake of brevity, these interfaces are referred to as TrAX (Transformations for XML).

There is a broad need for Java applications to be able to transform XML and related tree-shaped data structures. In fact, XML is not normally very useful to an application without going through some sort of transformation, unless the semantic structure is used directly as data. Almost all XML-related applications need to perform transformations. Transformations may be described by Java code, Perl code, XSLT Stylesheets, other types of script, or by proprietary formats. The inputs, one or multiple, to a transformation, may be a URL, XML stream, a DOM tree, SAX Events, or a proprietary format or data structure. The output types are the pretty much the same types as the inputs, but different inputs may need to be combined with different outputs.

The great challenge of a transformation API is how to deal with all the possible combinations of inputs and outputs, without becoming specialized for any of the given types.

The Java community will greatly benefit from a common API that will allow them to understand and apply a single model, write to consistent interfaces, and apply the transformations polymorphically. TrAX attempts to define a model that is clean and generic, yet fills general application requirements across a wide variety of uses.

General Terminology

This section will explain some general terminology used in this document. Technical terminology will be explained in the Model section. In many cases, the general terminology overlaps with the technical terminology.


The section defines the abstract model for TrAX, apart from the details of the interfaces.

A TRaX TransformerFactory is an object that processes transformation instructions, and produces Templates (in the technical terminology). A Templates object provides a Transformer, which transforms one or more Sources into one or more Results.

To use the TRaX interface, you create a TransformerFactory, which may directly provide a Transformers, or which can provide Templates from a variety of Sources. The Templates object is a processed or compiled representation of the transformation instructions, and provides a Transformer. The Transformer processes a Source according to the instructions found in the Templates, and produces a Result.

The process of transformation from a tree, either in the form of an object model, or in the form of parse events, into a stream, is known as serialization. We believe this is the most suitable term for this process, despite the overlap with Java object serialization.

TRaX Patterns