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package org.xml.sax;

import java.io.IOException;

/**

 * Interface for reading an XML document using callbacks.

 *

 *

 * <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 1.4, SAX 2.0

 * @author David Megginson

 * @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.

     *

     * <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.

     *

     * <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.

     *

     * <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.

     *

     * <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.

     *

     * <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.

     *

     * @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.

     * @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.

     * @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.

     * @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.

     * 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).

     *

     * <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;

}