Java API for XML Processing

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The Java API for XML Processing, or JAXP (pronounced jaks-p), is one of the Java XML programming APIs. It provides the capability of validating and parsing XML documents. The three basic parsing interfaces are:

the Document Object Model parsing interface or DOM interface
the Simple API for XML parsing interface or SAX interface
the Streaming API for XML or StAX interface (added in JDK 6; separate jar available for JDK 5)

In addition to the parsing interfaces, the API provides an XSLT interface to provide data and structural transformations on an XML document. JAXP was developed under the Java Community Process as JSR 5 (JAXP 1.0) and JSR 63 (JAXP 1.1 and 1.2). J2SE 1.4 is the first version of Java that comes with an implementation of JAXP. JAXP version 1.4.2 was released on May 30, 2007. JAXP 1.3 was end-of-lifed on February 12, 2008.

1 DOM interface
2 SAX interface
3 XSLT interface
4 External links

[edit] DOM interface

The DOM interface is perhaps the easiest to understand. It parses an entire XML document and constructs a complete in-memory representation of the document using the classes modeling the concepts found in the Document Object Model(DOM) Level 2 Core Specification.

The DOM parser is called a DocumentBuilder, as it builds an in-memory Document representation. The javax.xml.parsers.DocumentBuilder is created by the javax.xml.parsers.DocumentBuilderFactory. The DocumentBuilder creates an org.w3c.dom.Document instance, which is a tree structure containing nodes in the XML Document. Each tree node in the structure implements the org.w3c.dom.Node interface. There are many different types of tree nodes, representing the type of data found in an XML document. The most important node types are:

element nodes which may have attributes
text nodes representing the text found between the start and end tags of a document element.

Refer to the Javadoc documentation of the Java package org.w3c.dom for a complete list of node types.

[edit] SAX interface

The SAX parser is called the SAXParser and is created by the javax.xml.parsers.SAXParserFactory. Unlike the DOM parser, the SAX parser does not create an in-memory representation of the XML document and so is faster and uses less memory. Instead, the SAX parser informs clients of the XML document structure by invoking callbacks, that is, by invoking methods on a org.xml.sax.helpers.DefaultHandler instance provided to the parser.

The DefaultHandler class implements the ContentHandler, the ErrorHandler, the DTDHandler, and the EntityResolver interfaces. Most clients will be interested in methods defined in the ContentHandler interface which are called when the SAX parser encounters the corresponding elements in the XML document. The most important methods in this interface are:

startDocument() and endDocument() methods that are called at the start and end of an XML document.
startElement() and endElement() methods that are called at the start and end of a document element.
characters() method that is called with the text data contents contained between the start and end tags of an XML document element.

Clients provide a subclass of the DefaultHandler that overrides these methods and processes the data. This may involve storing the data into a database or writing it out to a stream.