Here is a summary of the key SAX APIs:
| Class | Usage |
|---|---|
| SAXParserFactory | Creates an instance of the parser determined by the system property, javax.xml.parsers.SAXParserFactory. |
| SAXParser | The SAXParser interface defines several overloaded of parse() methods. |
| SAXReader | The SAXParser wraps a SAXReader and is returned from SAXParser's getXMLReader() method. |
| DefaultHandler | DefaultHandler implements the ContentHandler, ErrorHandler, DTDHandler, and EntityResolver interfaces. By using DefaultHandler we can override only the ones that we need to. |
| ContentHandler | This interface defines the call back methods, such as startDocument, endDocument, startElement, and endElement. These method are invoked when an XML tag is recognized. It also defines the methods characters() which is invoked when the parser encounters the text in an XML element. It defines processingInstruction() which is invoked when the parser encounters the inline processing instruction. |
| ErrorHandler | It uses error(), fatalError(), and warning() methods to response to various parsing errors. The default error handler only throws an exception for fatal errors and ignores validation errors. |
| DTDHandler | Used to processe a DTD |
| EntityResolver | Its resolveEntity() method is used to identify data. |
We usually implement most of the ContentHandler methods.
To provide a more robust implementation we may implement the methods from ErrorHandler.
The SAX parser is defined in the packages listed in the following Table .
| Packages | Description |
|---|---|
| org.xml.sax | Defines the SAX interfaces. |
| org.xml.sax.ext | Defines SAX extensions used for more advanced SAX processing. |
| org.xml.sax.helpers | Defines helper classes for SAX APIs. |
| javax.xml.parsers | Defines the SAXParserFactory class, which returns the SAXParser. |
javax.xml.parsers.DocumentBuilderFactory class returns a DocumentBuilder instance.
We use DocumentBuilder instance to produce a Document object
out of an XML document.
The builder is determined by the system property javax.xml.parsers.DocumentBuilderFactory.
The newDocument() method from DocumentBuilder can
create an empty Document that implements the org.w3c.dom.Document interface.
We can use one of the builder's parse methods to create a Document
from existing XML document.
The Document Object Model implementation is defined in the packages listed in the following Table .
| Package | Description |
|---|---|
| org.w3c.dom | Defines the DOM programming interfaces for XML documents. |
| javax.xml.parsers | Defines the DocumentBuilderFactory class and
the DocumentBuilder class. |
A TransformerFactory creates a Transformer object.
The XSLT APIs are defined in the packages shown in the following Table .
| Package | Description |
|---|---|
| javax.xml.transform | Defines the TransformerFactory and Transformer classes.
We can invoke transform() method from the transformer object to do
the transformation. |
| javax.xml.transform.dom | Classes to create input and output objects from a DOM. |
| javax.xml.transform.sax | Classes to create input objects from a SAX parser and output objects from a SAX event handler. |
| javax.xml.transform.stream | Classes to create input objects and output objects from an I/O stream. |
StAX provides an alternative to SAX and DOM parsers for developers.
StAX can do high-performance stream filtering, processing, and modification with less memory.
StAX is a standard, bidirectional pull parser interface for streaming XML processing.
StAX offers a simpler programming model than SAX and is more memory efficient than DOM.
StAX can parse and modify XML streams as events.
The StAX APIs are defined in the packages shown in the following Table.
| Package | Description |
|---|---|
| javax.xml.stream | Defines the XMLStreamReader interface which iterates over the elements of an XML document.
Defines the XMLStreamWriter interface which specifies how the XML should be written. |
| javax.xml.transform.stax | Provides StAX-specific transformation APIs. |