// XMLReader.java - read an XML document.
// Written by David Megginson, sax@megginson.com
// NO WARRANTY! This class is in the Public Domain.
// $Id: XMLReader.java,v 1.6 2000/05/05 17:48:56 david Exp $
package org.xml.sax;
import java.io.IOException;
/**
* 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>
* </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
* Parser Parser} interface. The XMLReader interface
* contains two important enhancements over the old Parser
* interface:</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,
* <a href="mailto:sax@megginson.com">sax@megginson.com</a>
* @version 2.0
* @see XMLFilter
* @see org.xml.sax.helpers.ParserAdapter
* @see org.xml.sax.helpers.XMLReaderAdapter
*/
public interface XMLReader
{
////////////////////////////////////////////////////////////////////
// Configuration.
////////////////////////////////////////////////////////////////////
/**
* Look up the value of a feature.
*
* <p>The feature name is any fully-qualified URI. It is
* possible for an XMLReader to recognize a feature name but
* to be unable to return its value; this is especially true
* in the case of an adapter for a SAX1 Parser, which has
* no way of knowing whether the underlying parser is
* performing validation or expanding external entities.</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>Some feature values may be available only in specific
* contexts, such as before, during, or after a parse.</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 state of the feature (true or false).
* @exception SAXNotRecognizedException When the
* XMLReader does not recognize the feature name.
* @exception 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 state of a feature.
*
* <p>The feature name is any fully-qualified URI. It is
* possible for an XMLReader to recognize a feature name but
* to be unable to set its value; this is especially true
* in the case of an adapter for a SAX1 {@link Parser Parser},
* which has no way of affecting whether the underlying parser is
* validating, for example.</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>
*
* <p>Some feature values may be immutable or mutable only
* in specific contexts, such as before, during, or after
* a parse.</p>
*
* @param name The feature name, which is a fully-qualified URI.
* @param state The requested state of the feature (true or false).
* @exception SAXNotRecognizedException When the
* XMLReader does not recognize the feature name.
* @exception 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.
*
* <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 return its state; this is especially true
* in the case of an adapter for a SAX1 {@link Parser
* Parser}.</p>
*
* <p>XMLReaders are not required to recognize any specific
* property names, though an initial core set is documented for
* SAX2.</p>
*
* <p>Some property values may be available only in specific
* contexts, such as before, during, or after a parse.</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 SAXNotRecognizedException When the
* XMLReader does not recognize the property name.
* @exception 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.
*
* <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 set its value; this is especially true
* in the case of an adapter for a SAX1 {@link Parser
* Parser}.</p>
*
* <p>XMLReaders are not required to recognize setting
* any specific property names, though a core set is provided with
* SAX2.</p>
*
* <p>Some property values may be immutable or mutable only
* in specific contexts, such as before, during, or after
* a parse.</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 state The requested value for the property.
* @exception SAXNotRecognizedException When the
* XMLReader does not recognize the property name.
* @exception 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.
*
* <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.
* @exception NullPointerException If the resolver
* argument is null.
* @see #getEntityResolver
*/
public void setEntityResolver(EntityResolver resolver);
/**
* 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.
*
* <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.
* @exception NullPointerException If the handler
* argument is null.
* @see #getDTDHandler
*/
public void setDTDHandler(DTDHandler handler);
/**
* 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.
*
* <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.
* @exception NullPointerException If the handler
* argument is null.
* @see #getContentHandler
*/
public void setContentHandler(ContentHandler handler);
/**
* 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.
*
* <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.
* @exception NullPointerException If the handler
* argument is null.
* @see #getErrorHandler
*/
public void setErrorHandler(ErrorHandler handler);
/**
* 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.
*
* <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.</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 source The input source for the top-level of the
* XML document.
* @exception 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 InputSource
* @see #parse(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).
*
* <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 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(InputSource)
*/
public void parse(String systemId)
throws IOException, SAXException;
}
// end of XMLReader.java