http://xml.apache.org/commons/components/external/: xml-commons provides an Apache-hosted set of DOM, SAX, and JAXP interfaces for use in other xml-based projects. Our hope is that we can standardize on both a common version and packaging scheme for these critical XML standards interfaces to make the lives of both our developers and users easier. The External Components portion of xml-commons contains interfaces that are defined by external standards organizations. For DOM, that's the W3C; for SAX it's David Megginson and sax.sourceforge.net; for JAXP it's Sun. 
// XMLReader.java - read an XML document.
// http://www.saxproject.org
// Written by David Megginson
// NO WARRANTY!  This class is in the Public Domain.
// $Id: XMLReader.java 226184 2005-04-08 10:53:24Z neeraj $

package org.xml.sax;

import java.io.IOException;



Interface for reading an XML document using callbacks.


This module, both source code and documentation, is in the
Public Domain, and comes with NO WARRANTY.
See http://www.saxproject.org
for further information.



Note: despite its name, this interface does 
not extend the standard Java Reader interface, because reading XML is a fundamentally different activity than reading character data.


XMLReader is the interface that an XML parser's SAX2 driver must
implement.  This interface allows an application to set and
query features and properties in the parser, to register
event handlers for document processing, and to initiate
a document parse.


All SAX interfaces are assumed to be synchronous: the parse methods must not return until parsing is complete, and readers must wait for an event-handler callback to return before reporting the next event.


This interface replaces the (now deprecated) SAX 1.0 Parser interface. The XMLReader interface contains two important enhancements over the old Parser interface (as well as some minor ones):


    

  1. it adds a standard way to query and set features and 
 properties; and
    2. 

  2. it adds Namespace support, which is required for many
 higher-level XML standards.
    3. 



There are adapters available to convert a SAX1 Parser to
a SAX2 XMLReader and vice-versa.


Author:David Megginson
See Also:
Since:SAX 2.0
Version:2.0.1+ (sax2r3pre1)
/**
 * Interface for reading an XML document using callbacks.
 *
 * <blockquote>
 * <em>This module, both source code and documentation, is in the
 * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
 * See <a href='http://www.saxproject.org'>http://www.saxproject.org</a>
 * for further information.
 * </blockquote>
 *
 * <p><strong>Note:</strong> despite its name, this interface does 
 * <em>not</em> extend the standard Java {@link java.io.Reader Reader} 
 * interface, because reading XML is a fundamentally different activity 
 * than reading character data.</p>
 *
 * <p>XMLReader is the interface that an XML parser's SAX2 driver must
 * implement.  This interface allows an application to set and
 * query features and properties in the parser, to register
 * event handlers for document processing, and to initiate
 * a document parse.</p>
 *
 * <p>All SAX interfaces are assumed to be synchronous: the
 * {@link #parse parse} methods must not return until parsing
 * is complete, and readers must wait for an event-handler callback
 * to return before reporting the next event.</p>
 *
 * <p>This interface replaces the (now deprecated) SAX 1.0 {@link
 * org.xml.sax.Parser Parser} interface.  The XMLReader interface
 * contains two important enhancements over the old Parser
 * interface (as well as some minor ones):</p>
 *
 * <ol>
 * <li>it adds a standard way to query and set features and 
 *  properties; and</li>
 * <li>it adds Namespace support, which is required for many
 *  higher-level XML standards.</li>
 * </ol>
 *
 * <p>There are adapters available to convert a SAX1 Parser to
 * a SAX2 XMLReader and vice-versa.</p>
 *
 * @since SAX 2.0
 * @author David Megginson
 * @version 2.0.1+ (sax2r3pre1)
 * @see org.xml.sax.XMLFilter
 * @see org.xml.sax.helpers.ParserAdapter
 * @see org.xml.sax.helpers.XMLReaderAdapter 
 */
public interface XMLReader
{


    ////////////////////////////////////////////////////////////////////
    // Configuration.
    ////////////////////////////////////////////////////////////////////


    
Look up the value of a feature flag.

The feature name is any fully-qualified URI. It is possible for an XMLReader to recognize a feature name but temporarily be unable to return its value. Some feature values may be available only in specific contexts, such as before, during, or after a parse. Also, some feature values may not be programmatically accessible. (In the case of an adapter for SAX1 Parser, there is no implementation-independent way to expose whether the underlying parser is performing validation, expanding external entities, and so forth.) 


All XMLReaders are required to recognize the
http://xml.org/sax/features/namespaces and the
http://xml.org/sax/features/namespace-prefixes feature names.


Typical usage is something like this:


XMLReader r = new MySAXDriver();
                        // try to activate validation
try {
  r.setFeature("http://xml.org/sax/features/validation", true);
} catch (SAXException e) {
  System.err.println("Cannot activate validation."); 
}
                        // register event handlers
r.setContentHandler(new MyContentHandler());
r.setErrorHandler(new MyErrorHandler());
                        // parse the first document
try {
  r.parse("http://www.foo.com/mydoc.xml");
} catch (IOException e) {
  System.err.println("I/O exception reading XML document");
} catch (SAXException e) {
  System.err.println("XML exception reading document.");
}



Implementors are free (and encouraged) to invent their own features,
using names built on their own URIs.


Params:
  • name – The feature name, which is a fully-qualified URI.
Throws:
See Also:
Returns:The current value of the feature (true or false).
/**
     * Look up the value of a feature flag.
     *
     * <p>The feature name is any fully-qualified URI.  It is
     * possible for an XMLReader to recognize a feature name but
     * temporarily be unable to return its value.
     * Some feature values may be available only in specific
     * contexts, such as before, during, or after a parse.
     * Also, some feature values may not be programmatically accessible.
     * (In the case of an adapter for SAX1 {@link Parser}, there is no
     * implementation-independent way to expose whether the underlying
     * parser is performing validation, expanding external entities,
     * and so forth.) </p>
     *
     * <p>All XMLReaders are required to recognize the
     * http://xml.org/sax/features/namespaces and the
     * http://xml.org/sax/features/namespace-prefixes feature names.</p>
     *
     * <p>Typical usage is something like this:</p>
     *
     * <pre>
     * XMLReader r = new MySAXDriver();
     *
     *                         // try to activate validation
     * try {
     *   r.setFeature("http://xml.org/sax/features/validation", true);
     * } catch (SAXException e) {
     *   System.err.println("Cannot activate validation."); 
     * }
     *
     *                         // register event handlers
     * r.setContentHandler(new MyContentHandler());
     * r.setErrorHandler(new MyErrorHandler());
     *
     *                         // parse the first document
     * try {
     *   r.parse("http://www.foo.com/mydoc.xml");
     * } catch (IOException e) {
     *   System.err.println("I/O exception reading XML document");
     * } catch (SAXException e) {
     *   System.err.println("XML exception reading document.");
     * }
     * </pre>
     *
     * <p>Implementors are free (and encouraged) to invent their own features,
     * using names built on their own URIs.</p>
     *
     * @param name The feature name, which is a fully-qualified URI.
     * @return The current value of the feature (true or false).
     * @exception org.xml.sax.SAXNotRecognizedException If the feature
     *            value can't be assigned or retrieved.
     * @exception org.xml.sax.SAXNotSupportedException When the
     *            XMLReader recognizes the feature name but 
     *            cannot determine its value at this time.
     * @see #setFeature
     */
    public boolean getFeature (String name)
        throws SAXNotRecognizedException, SAXNotSupportedException;


    
Set the value of a feature flag.

The feature name is any fully-qualified URI.  It is
possible for an XMLReader to expose a feature value but
to be unable to change the current value.
Some feature values may be immutable or mutable only 
in specific contexts, such as before, during, or after 
a parse.


All XMLReaders are required to support setting
http://xml.org/sax/features/namespaces to true and
http://xml.org/sax/features/namespace-prefixes to false.


Params:
  • name – The feature name, which is a fully-qualified URI.
  • value – The requested value of the feature (true or false).
Throws:
See Also:
/**
     * Set the value of a feature flag.
     *
     * <p>The feature name is any fully-qualified URI.  It is
     * possible for an XMLReader to expose a feature value but
     * to be unable to change the current value.
     * Some feature values may be immutable or mutable only 
     * in specific contexts, such as before, during, or after 
     * a parse.</p>
     *
     * <p>All XMLReaders are required to support setting
     * http://xml.org/sax/features/namespaces to true and
     * http://xml.org/sax/features/namespace-prefixes to false.</p>
     *
     * @param name The feature name, which is a fully-qualified URI.
     * @param value The requested value of the feature (true or false).
     * @exception org.xml.sax.SAXNotRecognizedException If the feature
     *            value can't be assigned or retrieved.
     * @exception org.xml.sax.SAXNotSupportedException When the
     *            XMLReader recognizes the feature name but 
     *            cannot set the requested value.
     * @see #getFeature
     */
    public void setFeature (String name, boolean value)
	throws SAXNotRecognizedException, SAXNotSupportedException;


    
Look up the value of a property.

The property name is any fully-qualified URI.  It is
possible for an XMLReader to recognize a property name but
temporarily be unable to return its value.
Some property values may be available only in specific
contexts, such as before, during, or after a parse.


XMLReaders are not required to recognize any specific
property names, though an initial core set is documented for
SAX2.


Implementors are free (and encouraged) to invent their own properties,
using names built on their own URIs.


Params:
  • name – The property name, which is a fully-qualified URI.
Throws:
See Also:
Returns:The current value of the property.
/**
     * Look up the value of a property.
     *
     * <p>The property name is any fully-qualified URI.  It is
     * possible for an XMLReader to recognize a property name but
     * temporarily be unable to return its value.
     * Some property values may be available only in specific
     * contexts, such as before, during, or after a parse.</p>
     *
     * <p>XMLReaders are not required to recognize any specific
     * property names, though an initial core set is documented for
     * SAX2.</p>
     *
     * <p>Implementors are free (and encouraged) to invent their own properties,
     * using names built on their own URIs.</p>
     *
     * @param name The property name, which is a fully-qualified URI.
     * @return The current value of the property.
     * @exception org.xml.sax.SAXNotRecognizedException If the property
     *            value can't be assigned or retrieved.
     * @exception org.xml.sax.SAXNotSupportedException When the
     *            XMLReader recognizes the property name but 
     *            cannot determine its value at this time.
     * @see #setProperty
     */
    public Object getProperty (String name)
	throws SAXNotRecognizedException, SAXNotSupportedException;


    
Set the value of a property.

The property name is any fully-qualified URI.  It is
possible for an XMLReader to recognize a property name but
to be unable to change the current value.
Some property values may be immutable or mutable only 
in specific contexts, such as before, during, or after 
a parse.


XMLReaders are not required to recognize setting
any specific property names, though a core set is defined by 
SAX2.


This method is also the standard mechanism for setting
extended handlers.


Params:
  • name – The property name, which is a fully-qualified URI.
  • value – The requested value for the property.
Throws:
/**
     * Set the value of a property.
     *
     * <p>The property name is any fully-qualified URI.  It is
     * possible for an XMLReader to recognize a property name but
     * to be unable to change the current value.
     * Some property values may be immutable or mutable only 
     * in specific contexts, such as before, during, or after 
     * a parse.</p>
     *
     * <p>XMLReaders are not required to recognize setting
     * any specific property names, though a core set is defined by 
     * SAX2.</p>
     *
     * <p>This method is also the standard mechanism for setting
     * extended handlers.</p>
     *
     * @param name The property name, which is a fully-qualified URI.
     * @param value The requested value for the property.
     * @exception org.xml.sax.SAXNotRecognizedException If the property
     *            value can't be assigned or retrieved.
     * @exception org.xml.sax.SAXNotSupportedException When the
     *            XMLReader recognizes the property name but 
     *            cannot set the requested value.
     */
    public void setProperty (String name, Object value)
	throws SAXNotRecognizedException, SAXNotSupportedException;



    ////////////////////////////////////////////////////////////////////
    // Event handlers.
    ////////////////////////////////////////////////////////////////////


    
Allow an application to register an entity resolver.

If the application does not register an entity resolver,
the XMLReader will perform its own default resolution.


Applications may register a new or different resolver in the
middle of a parse, and the SAX parser must begin using the new
resolver immediately.


Params:
  • resolver – The entity resolver.
See Also:
/**
     * Allow an application to register an entity resolver.
     *
     * <p>If the application does not register an entity resolver,
     * the XMLReader will perform its own default resolution.</p>
     *
     * <p>Applications may register a new or different resolver in the
     * middle of a parse, and the SAX parser must begin using the new
     * resolver immediately.</p>
     *
     * @param resolver The entity resolver.
     * @see #getEntityResolver
     */
    public void setEntityResolver (EntityResolver resolver);


    
Return the current entity resolver.

See Also:
Returns:The current entity resolver, or null if none
        has been registered.
/**
     * Return the current entity resolver.
     *
     * @return The current entity resolver, or null if none
     *         has been registered.
     * @see #setEntityResolver
     */
    public EntityResolver getEntityResolver ();


    
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.


Params:
  • handler – The DTD handler.
See Also:
/**
     * Allow an application to register a DTD event handler.
     *
     * <p>If the application does not register a DTD handler, all DTD
     * events reported by the SAX parser will be silently ignored.</p>
     *
     * <p>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.</p>
     *
     * @param handler The DTD handler.
     * @see #getDTDHandler
     */
    public void setDTDHandler (DTDHandler handler);


    
Return the current DTD handler.

See Also:
Returns:The current DTD handler, or null if none
        has been registered.
/**
     * Return the current DTD handler.
     *
     * @return The current DTD handler, or null if none
     *         has been registered.
     * @see #setDTDHandler
     */
    public DTDHandler getDTDHandler ();


    
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.


Params:
  • handler – The content handler.
See Also:
/**
     * Allow an application to register a content event handler.
     *
     * <p>If the application does not register a content handler, all
     * content events reported by the SAX parser will be silently
     * ignored.</p>
     *
     * <p>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.</p>
     *
     * @param handler The content handler.
     * @see #getContentHandler
     */
    public void setContentHandler (ContentHandler handler);


    
Return the current content handler.

See Also:
Returns:The current content handler, or null if none
        has been registered.
/**
     * Return the current content handler.
     *
     * @return The current content handler, or null if none
     *         has been registered.
     * @see #setContentHandler
     */
    public ContentHandler getContentHandler ();


    
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.


Params:
  • handler – The error handler.
See Also:
/**
     * Allow an application to register an error event handler.
     *
     * <p>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.</p>
     *
     * <p>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.</p>
     *
     * @param handler The error handler.
     * @see #getErrorHandler
     */
    public void setErrorHandler (ErrorHandler handler);


    
Return the current error handler.

See Also:
Returns:The current error handler, or null if none
        has been registered.
/**
     * Return the current error handler.
     *
     * @return The current error handler, or null if none
     *         has been registered.
     * @see #setErrorHandler
     */
    public ErrorHandler getErrorHandler ();



    ////////////////////////////////////////////////////////////////////
    // Parsing.
    ////////////////////////////////////////////////////////////////////

    
Parse 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.
Configuration of the XMLReader object (such as handler bindings and
values established for feature flags and properties) is unchanged
by completion of a parse, unless the definition of that aspect of
the configuration explicitly specifies other behavior.
(For example, feature flags or properties exposing
characteristics of the document being parsed.)



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.


Params:
  • input – The input source for the top-level of the
       XML document.
Throws:
  • SAXException – Any SAX exception, possibly
           wrapping another exception.
  • IOException – An IO exception from the parser,
           possibly from a byte stream or character stream
           supplied by the application.
See Also:
/**
     * Parse an XML document.
     *
     * <p>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).</p>
     *
     * <p>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.
     * Configuration of the XMLReader object (such as handler bindings and
     * values established for feature flags and properties) is unchanged
     * by completion of a parse, unless the definition of that aspect of
     * the configuration explicitly specifies other behavior.
     * (For example, feature flags or properties exposing
     * characteristics of the document being parsed.)
     * </p>
     *
     * <p>During the parse, the XMLReader will provide information
     * about the XML document through the registered event
     * handlers.</p>
     *
     * <p>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.</p>
     *
     * @param input The input source for the top-level of the
     *        XML document.
     * @exception org.xml.sax.SAXException Any SAX exception, possibly
     *            wrapping another exception.
     * @exception java.io.IOException An IO exception from the parser,
     *            possibly from a byte stream or character stream
     *            supplied by the application.
     * @see org.xml.sax.InputSource
     * @see #parse(java.lang.String)
     * @see #setEntityResolver
     * @see #setDTDHandler
     * @see #setContentHandler
     * @see #setErrorHandler 
     */
    public void parse (InputSource input)
	throws IOException, SAXException;


    
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.  It is the exact
equivalent of the following:


parse(new InputSource(systemId));



If the system identifier is a URL, it must be fully resolved
by the application before it is passed to the parser.


Params:
  • systemId – The system identifier (URI).
Throws:
  • SAXException – Any SAX exception, possibly
           wrapping another exception.
  • IOException – An IO exception from the parser,
           possibly from a byte stream or character stream
           supplied by the application.
See Also:
/**
     * Parse an XML document from a system identifier (URI).
     *
     * <p>This method is a shortcut for the common case of reading a
     * document from a system identifier.  It is the exact
     * equivalent of the following:</p>
     *
     * <pre>
     * parse(new InputSource(systemId));
     * </pre>
     *
     * <p>If the system identifier is a URL, it must be fully resolved
     * by the application before it is passed to the parser.</p>
     *
     * @param systemId The system identifier (URI).
     * @exception org.xml.sax.SAXException Any SAX exception, possibly
     *            wrapping another exception.
     * @exception java.io.IOException An IO exception from the parser,
     *            possibly from a byte stream or character stream
     *            supplied by the application.
     * @see #parse(org.xml.sax.InputSource)
     */
    public void parse (String systemId)
	throws IOException, SAXException;

}