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The Axiom API
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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.axiom.om.impl.serialize;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.apache.axiom.om.OMAttribute;
import org.apache.axiom.om.OMComment;
import org.apache.axiom.om.OMElement;
import org.apache.axiom.om.OMNamespace;
import org.apache.axiom.om.OMNode;
import org.apache.axiom.om.OMText;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.DTDHandler;
import org.xml.sax.EntityResolver;
import org.xml.sax.ErrorHandler;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.SAXNotRecognizedException;
import org.xml.sax.SAXNotSupportedException;
import org.xml.sax.XMLReader;
import org.xml.sax.ext.LexicalHandler;

/**
 * SAX {@link XMLReader} implementation that traverses a given OM tree and invokes the
 * callback methods on the configured {@link ContentHandler}. This can be used to
 * serialize an Axiom tree to SAX.
 */
public class OMXMLReader implements XMLReader {
    private static final String URI_LEXICAL_HANDLER = "http://xml.org/sax/properties/lexical-handler";
    
    private final OMElement element;
    private final AttributesAdapter attributesAdapter = new AttributesAdapter();
    
    private boolean namespaces = true;
    private boolean namespacePrefixes = false;
    
    private ContentHandler contentHandler;
    private LexicalHandler lexicalHandler;
    private DTDHandler dtdHandler;
    private EntityResolver entityResolver;
    private ErrorHandler errorHandler;
    
    public OMXMLReader(OMElement element) {
        this.element = element;
    }

    public ContentHandler getContentHandler() {
        return contentHandler;
    }

    public void setContentHandler(ContentHandler contentHandler) {
        this.contentHandler = contentHandler;
    }

    public DTDHandler getDTDHandler() {
        return dtdHandler;
    }

    public void setDTDHandler(DTDHandler dtdHandler) {
        this.dtdHandler = dtdHandler;
    }

    public EntityResolver getEntityResolver() {
        return entityResolver;
    }

    public void setEntityResolver(EntityResolver entityResolver) {
        this.entityResolver = entityResolver;
    }

    public ErrorHandler getErrorHandler() {
        return errorHandler;
    }

    public void setErrorHandler(ErrorHandler errorHandler) {
        this.errorHandler = errorHandler;
    }

    public boolean getFeature(String name)
            throws SAXNotRecognizedException, SAXNotSupportedException {
        throw new SAXNotRecognizedException(name);
    }

    public void setFeature(String name, boolean value)
            throws SAXNotRecognizedException, SAXNotSupportedException {
        
        if ("http://xml.org/sax/features/namespaces".equals(name)) {
            namespaces = value;
        } else if ("http://xml.org/sax/features/namespace-prefixes".equals(name)) {
            namespacePrefixes = value;
        } else {
            throw new SAXNotRecognizedException(name);
        }
    }

    public Object getProperty(String name)
            throws SAXNotRecognizedException, SAXNotSupportedException {
        
        if ("http://xml.org/sax/features/namespaces".equals(name)) {
            return Boolean.valueOf(namespaces);
        } else if ("http://xml.org/sax/features/namespace-prefixes".equals(name)) {
            return Boolean.valueOf(namespacePrefixes);
        } else if (URI_LEXICAL_HANDLER.equals(name)) {
            return lexicalHandler;
        } else {
            throw new SAXNotRecognizedException(name);
        }
    }

    public void setProperty(String name, Object value)
            throws SAXNotRecognizedException, SAXNotSupportedException {
        if (URI_LEXICAL_HANDLER.equals(name)) {
            lexicalHandler = (LexicalHandler)value;
        } else {
            throw new SAXNotRecognizedException(name);
        }
    }

    public void parse(InputSource input) throws IOException, SAXException {
        parse();
    }

    public void parse(String systemId) throws IOException, SAXException {
        parse();
    }
    
    private void parse() throws SAXException {
        contentHandler.startDocument();
        generateEvents(element);
        contentHandler.endDocument();
    }
    
    private void generatePrefixMappingEvents(OMElement omElement, boolean start)
            throws SAXException {
        
        for (Iterator it = omElement.getAllDeclaredNamespaces(); it.hasNext(); ) {
            OMNamespace ns = (OMNamespace)it.next();
            String prefix = ns.getPrefix();
            if (prefix != null) {
                if (start) {
                    contentHandler.startPrefixMapping(prefix, ns.getNamespaceURI());
                } else {
                    contentHandler.endPrefixMapping(prefix);
                }
            }
        }
    }
    
    private void generateEvents(OMElement omElement) throws SAXException {
        generatePrefixMappingEvents(omElement, true);
        OMNamespace omNamespace = omElement.getNamespace();
        String uri;
        String prefix;
        if (omNamespace != null) {
            uri = omNamespace.getNamespaceURI();
            prefix = omNamespace.getPrefix();
        } else {
            uri = "";
            prefix = null;
        }
        String localName = omElement.getLocalName();
        String qName;
        if (prefix == null || prefix.length() == 0) {
            qName = localName;
        } else {
            qName = prefix + ":" + localName;
        }
        // For performance reasons, we always reuse the same instance of AttributesAdapter.
        // This is explicitely allowed by the specification of the startElement method.
        attributesAdapter.setAttributes(omElement);
        contentHandler.startElement(uri, localName, qName, attributesAdapter);
        for (Iterator it = omElement.getChildren(); it.hasNext(); ) {
            OMNode node = (OMNode)it.next();
            switch (node.getType()) {
                case OMNode.ELEMENT_NODE:
                    generateEvents((OMElement)node);
                    break;
                case OMNode.TEXT_NODE:
                    generateEvents((OMText)node);
                    break;
                case OMNode.CDATA_SECTION_NODE:
                    if (lexicalHandler != null) {
                        lexicalHandler.startCDATA();
                    }
                    generateEvents((OMText)node);
                    if (lexicalHandler != null) {
                        lexicalHandler.endCDATA();
                    }
                    break;
                case OMNode.COMMENT_NODE:
                    if (lexicalHandler != null) {
                        char[] ch = ((OMComment)node).getValue().toCharArray();
                        lexicalHandler.comment(ch, 0, ch.length);
                    }
            }
        }
        contentHandler.endElement(uri, localName, qName);
        generatePrefixMappingEvents(omElement, false);
    }
    
    private void generateEvents(OMText omText) throws SAXException {
        char[] ch = omText.getTextCharacters();
        contentHandler.characters(ch, 0, ch.length);
    }

    protected static class AttributesAdapter implements Attributes {
        private List/**/ attributes = new ArrayList(5);

        public void setAttributes(OMElement element) {
            attributes.clear();
            for (Iterator it = element.getAllAttributes(); it.hasNext(); ) {
                attributes.add(it.next());
            }
        }

        public int getLength() {
            return attributes.size();
        }

        public int getIndex(String qName) {
            for (int i=0, len=attributes.size(); i