xmlfilterimpl.java

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// XMLFilterImpl.java - base SAX2 filter implementation.
// Written by David Megginson, [e-mail]
// NO WARRANTY!  This class is in the Public Domain.

// $Id: XMLFilterImpl.java,v 1.3 2000/05/15 16:10:53 mojo Exp $

package org.xml.sax.helpers;

import java.io.IOException;

import org.xml.sax.XMLReader;
import org.xml.sax.XMLFilter;
import org.xml.sax.InputSource;
import org.xml.sax.Locator;
import org.xml.sax.Attributes;
import org.xml.sax.EntityResolver;
import org.xml.sax.DTDHandler;
import org.xml.sax.ContentHandler;
import org.xml.sax.ErrorHandler;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.SAXNotSupportedException;
import org.xml.sax.SAXNotRecognizedException;


/**
 * Base class for deriving an XML filter.
 *
 * <blockquote>
 * <em>This module, both source code and documentation, is in the
 * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
 * </blockquote>
 *
 * <p>This class is designed to sit between an {@link org.xml.sax.XMLReader
 * XMLReader} and the client application's event handlers.  By default, it
 * does nothing but pass requests up to the reader and events
 * on to the handlers unmodified, but subclasses can override
 * specific methods to modify the event stream or the configuration
 * requests as they pass through.</p>
 *
 * @since SAX 2.0
 * @author David Megginson, 
 *         <a href="mailto:[e-mail]">[e-mail]</a>
 * @version 2.0
 * @see org.xml.sax.XMLFilter
 * @see org.xml.sax.XMLReader
 * @see org.xml.sax.EntityResolver
 * @see org.xml.sax.DTDHandler
 * @see org.xml.sax.ContentHandler
 * @see org.xml.sax.ErrorHandler
 */
public class XMLFilterImpl
    implements XMLFilter, EntityResolver, DTDHandler, ContentHandler, ErrorHandler
{


    ////////////////////////////////////////////////////////////////////
    // Constructors.
    ////////////////////////////////////////////////////////////////////


    /**
     * Construct an empty XML filter, with no parent.
     *
     * <p>This filter will have no parent: you must assign a parent
     * before you start a parse or do any configuration with
     * setFeature or setProperty.</p>
     *
     * @see org.xml.sax.XMLReader#setFeature
     * @see org.xml.sax.XMLReader#setProperty
     */
    public XMLFilterImpl ()
    {
	super();
    }


    /**
     * Construct an XML filter with the specified parent.
     *
     * @see #setParent
     * @see #getParent
     */
    public XMLFilterImpl (XMLReader parent)
    {
        super();
	setParent(parent);
    }



    ////////////////////////////////////////////////////////////////////
    // Implementation of org.xml.sax.XMLFilter.
    ////////////////////////////////////////////////////////////////////


    /**
     * Set the parent reader.
     *
     * <p>This is the {@link org.xml.sax.XMLReader XMLReader} from which 
     * this filter will obtain its events and to which it will pass its 
     * configuration requests.  The parent may itself be another filter.</p>
     *
     * <p>If there is no parent reader set, any attempt to parse
     * or to set or get a feature or property will fail.</p>
     *
     * @param parent The parent XML reader.
     * @exception java.lang.NullPointerException If the parent is null.
     * @see #getParent
     */
    public void setParent (XMLReader parent)
    {
	if (parent == null) {
	    throw new NullPointerException("Null parent");
	}
	this.parent = parent;
    }


    /**
     * Get the parent reader.
     *
     * @return The parent XML reader, or null if none is set.
     * @see #setParent
     */
    public XMLReader getParent ()
    {
	return parent;
    }



    ////////////////////////////////////////////////////////////////////
    // Implementation of org.xml.sax.XMLReader.
    ////////////////////////////////////////////////////////////////////


    /**
     * Set the state of a feature.
     *
     * <p>This will always fail if the parent is null.</p>
     *
     * @param name The feature name.
     * @param state The requested feature state.
     * @exception org.xml.sax.SAXNotRecognizedException When the
     *            XMLReader does not recognize the feature name.
     * @exception org.xml.sax.SAXNotSupportedException When the
     *            XMLReader recognizes the feature name but 
     *            cannot set the requested value.
     * @see org.xml.sax.XMLReader#setFeature
     */
    public void setFeature (String name, boolean state)
	throws SAXNotRecognizedException, SAXNotSupportedException
    {
	if (parent != null) {
	    parent.setFeature(name, state);
	} else {
	    throw new SAXNotRecognizedException("Feature: " + name);
	}
    }


    /**
     * Look up the state of a feature.
     *
     * <p>This will always fail if the parent is null.</p>
     *
     * @param name The feature name.
     * @return The current state of the feature.
     * @exception org.xml.sax.SAXNotRecognizedException When the
     *            XMLReader does not recognize the feature name.
     * @exception org.xml.sax.SAXNotSupportedException When the
     *            XMLReader recognizes the feature name but 
     *            cannot determine its state at this time.
     * @see org.xml.sax.XMLReader#getFeature
     */
    public boolean getFeature (String name)
	throws SAXNotRecognizedException, SAXNotSupportedException
    {
	if (parent != null) {
	    return parent.getFeature(name);
	} else {
	    throw new SAXNotRecognizedException("Feature: " + name);
	}
    }


    /**
     * Set the value of a property.
     *
     * <p>This will always fail if the parent is null.</p>
     *
     * @param name The property name.
     * @param state The requested property value.
     * @exception org.xml.sax.SAXNotRecognizedException When the
     *            XMLReader does not recognize the property name.
     * @exception org.xml.sax.SAXNotSupportedException When the
     *            XMLReader recognizes the property name but 
     *            cannot set the requested value.
     * @see org.xml.sax.XMLReader#setProperty
     */
    public void setProperty (String name, Object value)
	throws SAXNotRecognizedException, SAXNotSupportedException
    {
	if (parent != null) {
	    parent.setProperty(name, value);
	} else {
	    throw new SAXNotRecognizedException("Property: " + name);
	}
    }


    /**
     * Look up the value of a property.
     *
     * @param name The property name.
     * @return The current value of the property.
     * @exception org.xml.sax.SAXNotRecognizedException When the
     *            XMLReader does not recognize the feature name.
     * @exception org.xml.sax.SAXNotSupportedException When the
     *            XMLReader recognizes the property name but 
     *            cannot determine its value at this time.
     * @see org.xml.sax.XMLReader#setFeature
     */
    public Object getProperty (String name)
	throws SAXNotRecognizedException, SAXNotSupportedException
    {
	if (parent != null) {
	    return parent.getProperty(name);
	} else {
	    throw new SAXNotRecognizedException("Property: " + name);
	}
    }


    /**
     * Set the entity resolver.
     *
     * @param resolver The new entity resolver.
     * @exception java.lang.NullPointerException If the resolver
     *            is null.
     * @see org.xml.sax.XMLReader#setEntityResolver
     */
    public void setEntityResolver (EntityResolver resolver)
    {
	if (resolver == null) {
	    throw new NullPointerException("Null entity resolver");
	} else {
	    entityResolver = resolver;
	}
    }


    /**
     * Get the current entity resolver.
     *
     * @return The current entity resolver, or null if none was set.
     * @see org.xml.sax.XMLReader#getEntityResolver
     */
    public EntityResolver getEntityResolver ()
    {
	return entityResolver;
    }


    /**
     * Set the DTD event handler.
     *
     * @param resolver The new DTD handler.
     * @exception java.lang.NullPointerException If the handler
     *            is null.
     * @see org.xml.sax.XMLReader#setDTDHandler
     */
    public void setDTDHandler (DTDHandler handler)
    {
	if (handler == null) {
	    throw new NullPointerException("Null DTD handler");
	} else {
	    dtdHandler = handler;
	}
    }


    /**
     * Get the current DTD event handler.
     *
     * @return The current DTD handler, or null if none was set.
     * @see org.xml.sax.XMLReader#getDTDHandler
     */
    public DTDHandler getDTDHandler ()
    {
	return dtdHandler;
    }


    /**
     * Set the content event handler.
     *
     * @param resolver The new content handler.
     * @exception java.lang.NullPointerException If the handler
     *            is null.
     * @see org.xml.sax.XMLReader#setContentHandler
     */
    public void setContentHandler (ContentHandler handler)
    {
	if (handler == null) {
	    throw new NullPointerException("Null content handler");
	} else {
	    contentHandler = handler;
	}
    }


    /**
     * Get the content event handler.
     *
     * @return The current content handler, or null if none was set.
     * @see org.xml.sax.XMLReader#getContentHandler
     */
    public ContentHandler getContentHandler ()
    {
	return contentHandler;
    }


    /**
     * Set the error event handler.
     *
     * @param handle The new error handler.
     * @exception java.lang.NullPointerException If the handler
     *            is null.
     * @see org.xml.sax.XMLReader#setErrorHandler
     */
    public void setErrorHandler (ErrorHandler handler)
    {
	if (handler == null) {
	    throw new NullPointerException("Null error handler");
	} else {
	    errorHandler = handler;
	}
    }


    /**
     * Get the current error event handler.
     *
     * @return The current error handler, or null if none was set.
     * @see org.xml.sax.XMLReader#getErrorHandler
     */
    public ErrorHandler getErrorHandler ()
    {
	return errorHandler;
    }


    /**
     * Parse a document.
     *
     * @param input The input source for the document entity.
     * @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.XMLReader#parse(org.xml.sax.InputSource)
     */
    public void parse (InputSource input)
	throws SAXException, IOException
    {
	setupParse();
	parent.parse(input);
    }


    /**
     * Parse a document.
     *
     * @param systemId The system identifier as a fully-qualified 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 org.xml.sax.XMLReader#parse(java.lang.String)
     */