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/* XMLEntityResolver.java                                          NanoXML/Java

 *

 * $Revision: 1.1 $

 * $Date: 2006/06/14 07:29:07 $

 * $Name:  $

 *

 * This file is part of NanoXML 2 for Java.

 * Copyright (C) 2001 Marc De Scheemaecker, All Rights Reserved.

 *

 * This software is provided 'as-is', without any express or implied warranty.

 * In no event will the authors be held liable for any damages arising from the

 * use of this software.

 *

 * Permission is granted to anyone to use this software for any purpose,

 * including commercial applications, and to alter it and redistribute it

 * freely, subject to the following restrictions:

 *

 *  1. The origin of this software must not be misrepresented; you must not

 *     claim that you wrote the original software. If you use this software in

 *     a product, an acknowledgment in the product documentation would be

 *     appreciated but is not required.

 *

 *  2. Altered source versions must be plainly marked as such, and must not be

 *     misrepresented as being the original software.

 *

 *  3. This notice may not be removed or altered from any source distribution.

 */

package net.n3.nanoxml;

import java.io.Reader;

import java.io.StringReader;

import java.util.Hashtable;

/**

 * An XMLEntityResolver resolves entities.

 *

 * @author Marc De Scheemaecker

 * @version $Name:  $, $Revision: 1.1 $

 */

public class XMLEntityResolver

    implements IXMLEntityResolver

{

    /**

     * The entities.

     */

    private Hashtable entities;

    /**

     * Initializes the resolver.

     */

    public XMLEntityResolver()

    {

        this.entities = new Hashtable();

        this.entities.put("amp", "&");

        this.entities.put("quot", """);

        this.entities.put("apos", "'");

        this.entities.put("lt", "<");

        this.entities.put("gt", ">");

    }

    /**

     * Cleans up the object when it's destroyed.

     */

    protected void finalize()

        throws Throwable

    {

        this.entities.clear();

        this.entities = null;

        super.finalize();

    }

    /**

     * Adds an internal entity.

     *

     * @param name the name of the entity.

     * @param value the value of the entity.

     */

    public void addInternalEntity(String name,

                                  String value)

    {

        if (! this.entities.containsKey(name)) {

            this.entities.put(name, value);

        }

    }

    /**

     * Adds an external entity.

     *

     * @param name the name of the entity.

     * @param publicID the public ID of the entity, which may be null.

     * @param systemID the system ID of the entity.

     */

    public void addExternalEntity(String name,

                                  String publicID,

                                  String systemID)

    {

        if (! this.entities.containsKey(name)) {

            this.entities.put(name, new String[] { publicID, systemID } );

        }

    }

    /**

     * Returns a Java reader containing the value of an entity.

     *

     * @param xmlReader the current XML reader

     * @param name the name of the entity.

     *

     * @return the reader, or null if the entity could not be resolved.

     */

    public Reader getEntity(IXMLReader xmlReader,

                            String     name)

        throws XMLParseException

    {

        Object obj = this.entities.get(name);

        if (obj == null) {

            return null;

        } else if (obj instanceof java.lang.String) {

            return new StringReader((String)obj);

        } else {

            String[] id = (String[]) obj;

            return this.openExternalEntity(xmlReader, id[0], id[1]);

        }

    }

    /**

     * Opens an external entity.

     *

     * @param xmlReader the current XML reader

     * @param publicID the public ID, which may be null

     * @param systemID the system ID

     *

     * @return the reader, or null if the reader could not be created/opened

     */

    protected Reader openExternalEntity(IXMLReader xmlReader,

                                        String     publicID,

                                        String     systemID)

        throws XMLParseException

    {

        try {

            return xmlReader.openStream(publicID, systemID);

        } catch (Exception e) {

            throw new XMLParseException(xmlReader.getSystemID(),

                                        xmlReader.getLineNr(),

                                        "Could not open external entity "

                                        + "at system ID: " + systemID);

        }

    }

}