The org.xml.sax.XMLReader Interface

Sub Interfaces: org.xml.sax.XMLFilter
Implementing classes: org.xml.sax.helpers.ParserAdapter, org.xml.sax.helpers.XMLFilterImpl

Members

Overview

This is the core interface that defines parsing behaviour in SAX2.0 is vendors XML parsing software must include at least one implementation of this interface. It replaces the SAX1.0 Parser interface by adding support for namespaces in a Document’s elements and attributes. In additing to providing an entry into parsing (with either a system ID or InputSource as input), it allows registering of the various handler interfaces that SAX2.0 provides. The features and properties available to a SAX parser implementation are also set through this interface.

Method Overviews

All most all methods in this interface are important. The implementation depends upon application requirement. I tried to give examples of methods that have come across during my execution and are also generally used across parsing specific applications.

Example of parse(InputSource input)

This method parses an XML document. The application can use this method to instruct the XML reader to begin parsing an XML document from any valid input source (a character stream, a byte stream, or a URI). Applications may not invoke this method while a parse is in progress (they should create a new XMLReader instead for each nested XML document). Once a parse is complete, an application may reuse the same XMLReader object, possibly with a different input source. During the parse, the XMLReader will provide information about the XML document through the registered event handlers. This method is synchronous: it will not return until parsing has ended. If a client application wants to terminate parsing early, it should throw an exception.

This method throws

      org.xml.sax.SAXException : This occurs when any error occurs during parsing.

      java.io.IOException : This occurs when any error occurs while reading an XML document from byte stream, character stream.

            InputSource source  = new InputSource(systemId);

            xmlReader.setContentHandler(contentHandler);

               xmlReader.parse(source);

Example of parse(String systemId)

Parse an XML document from a system identifier (URI). This method is a shortcut for the common case of reading a document from a system identifier. If the system identifier is a URL, it must be fully resolved by the application before it is passed to the parser.

This method throws :

      org.xml.sax.SAXException : This occurs when any error occurs during parsing.

      java.io.IOException : This occurs when any error occurs while reading an XML document from byte stream, character stream.

ContentHandlerImpl contentHandler = new ContentHandlerImpl();

               xmlReader.setContentHandler(contentHandler);

                xmlReader.parse(systemId);

Example of setContentHandler(ContentHandler handler)

Allow an application to register a content event handler. If the application does not register a content handler, all content events reported by the SAX parser will be silently ignored. Applications may register a new or different handler in the middle of a parse, and the SAX parser must begin using the new handler immediately.

This method throws :

            java.lang.NullPointerException : If the handler argument is null.

            ContentHandlerImpl contentHandler = new ContentHandlerImpl(); //this class implements ContentHandler interface

      xmlReader.setContentHandler(contentHandler);

Example of setErrorHandler(ErrorHandler handler)

Allow an application to register an error event handler. If the application does not register an error handler, all error events reported by the SAX parser will be silently ignored; however, normal processing may not continue. It is highly recommended that all SAX applications implement an error handler to avoid unexpected bugs. Applications may register a new or different handler in the middle of a parse, and the SAX parser must begin using the new handler immediately.

This method throws :

            java.lang.NullPointerException : If the handler argument is null.

ErrorHandlerImpl errorHandler = new ErrorHandlerImpl(); //This class implements ErrorHandler interface.

xmlReader.setErrorHandler(errorHandler);

Example of setDTDHandler(DTDHandler handler):

Allow an application to register a DTD event handler. If the application does not register a DTD handler, all DTD events reported by the SAX parser will be silently ignored. Applications may register a new or different handler in the middle of a parse, and the SAX parser must begin using the new handler immediately.

This method throws :

            java.lang.NullPointerException : If the handler argument is null.

DTDHandlerImpl dtdHandler = new DTDHandlerImpl();//This class implements DTDHandler impl.

xmlReader.setDTDHandler(dtdHandler);