JAXP Overview 

JAXP is a standard Sun API that allows different XML-processing Java software to be easily plugged in and interchanged. The whole process consists of simply changing a system property, without dealing with all the pre-existing code. Problems may occur if the new parser does not support some of the features that the old one supplied.

JAXP includes interfaces and abstract classes that ensure access to DOM and SAX parsers, as well as to XSLT transformers.

In order to obtain a SAXParser, the user must first get its corresponding SAXParserFactory through the static SAXParserFactory.newInstance() method and then the SAXParser itself by the factory newSAXParser()method.

Similarly, DocumentBuilder-s (DOM parsers) and their factories are obtained through DocumentBuilderFactory, and Transformer-s (XSLT transformers) are obtained through TransformerFactory. Every factory's newInstance() method checks the corresponding system property to obtain information on the name of the class that implements it. If no such property has been set, a default implementation is returned.

For instance, a SAXParser can be obtained through:

SAXParserFactory f = SAXParserFactory.newInstance();
SAXParser p = f.newSAXParser();

And used through:

org.xml.sax.helpers.DefaultHandler h = new MyHandler();
p.parse(filename, h);

The JAXP view of SAP J2EE Engine XML tools is placed in the com.sap.engine.lib.jaxp package. It supports the two basic API-s, DOM, SAX, and XSLT transformations.