JSONDataSource.java

/*
 * 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.tuscany.sca.databinding.json.axiom;

import java.io.IOException;
import java.io.OutputStream;
import java.io.Writer;
import java.util.HashMap;
import java.util.Map;

import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamReader;

import org.apache.axiom.om.OMDataSource;
import org.apache.axiom.om.OMException;
import org.apache.axiom.om.OMOutputFormat;
import org.codehaus.jettison.json.JSONObject;
import org.codehaus.jettison.json.JSONTokener;
import org.codehaus.jettison.mapped.MappedXMLInputFactory;

/**
 * JSONDataSource keeps the JSON String inside and consumes it when needed. This is to be kept in the
 * OMSourcedElementImpl and can be used either to expand the tree or get the JSON String directly without expanding.
 * This uses the "Mapped" JSON convention.
 *
 * @version $Rev$ $Date$
 */

public class JSONDataSource implements OMDataSource {
    protected JSONObject json;

    public JSONDataSource(JSONObject json) {
        this.json = json;
    }

    /**
     * Writes JSON into the output stream. As this should write JSON, it directly gets the JSON string and writes it
     * without expanding the tree.
     * 
     * @param outputStream the stream to be written into
     * @param omOutputFormat format of the message, this is ignored.
     * @throws javax.xml.stream.XMLStreamException if there is an error while writing the message in to the output
     *             stream.
     */
    public void serialize(OutputStream outputStream, OMOutputFormat omOutputFormat)
        throws javax.xml.stream.XMLStreamException {
        try {
            String encoding = omOutputFormat == null ? "UTF-8" : omOutputFormat.getCharSetEncoding();
            outputStream.write(getJSONString().getBytes(encoding));
        } catch (IOException e) {
            throw new OMException();
        }
    }

    /**
     * Writes JSON through the writer. As this should write JSON, it directly gets the JSON string and writes it without
     * expanding the tree.
     * 
     * @param writer Writer to be written into
     * @param omOutputFormat format of the message, this is ignored.
     * @throws javax.xml.stream.XMLStreamException if there is an error while writing the message through the writer.
     */
    public void serialize(Writer writer, OMOutputFormat omOutputFormat) throws javax.xml.stream.XMLStreamException {
        try {
            writer.write(getJSONString());
        } catch (IOException e) {
            throw new OMException();
        }
    }

    /**
     * Writes XML through the XMLStreamWriter. As the input data source is JSON, this method needs to get a StAX reader
     * from that JSON String. Therefore this uses the getReader() method to get the StAX reader writes the events into
     * the XMLStreamWriter.
     * 
     * @param xmlStreamWriter StAX writer to be written into
     * @throws javax.xml.stream.XMLStreamException if there is an error while writing the message through the StAX
     *             writer.
     */
    public void serialize(javax.xml.stream.XMLStreamWriter xmlStreamWriter) throws javax.xml.stream.XMLStreamException {
        XMLStreamReader reader = getReader();
        xmlStreamWriter.writeStartDocument();
        while (reader.hasNext()) {
            int x = reader.next();
            switch (x) {
                case XMLStreamConstants.START_ELEMENT:
                    xmlStreamWriter.writeStartElement(reader.getPrefix(), reader.getLocalName(), reader
                        .getNamespaceURI());
                    int namespaceCount = reader.getNamespaceCount();
                    for (int i = namespaceCount - 1; i >= 0; i--) {
                        xmlStreamWriter.writeNamespace(reader.getNamespacePrefix(i), reader.getNamespaceURI(i));
                    }
                    int attributeCount = reader.getAttributeCount();
                    for (int i = 0; i < attributeCount; i++) {
                        xmlStreamWriter.writeAttribute(reader.getAttributePrefix(i),
                                                       reader.getAttributeNamespace(i),
                                                       reader.getAttributeLocalName(i),
                                                       reader.getAttributeValue(i));
                    }
                    break;
                case XMLStreamConstants.START_DOCUMENT:
                    break;
                case XMLStreamConstants.CHARACTERS:
                    xmlStreamWriter.writeCharacters(reader.getText());
                    break;
                case XMLStreamConstants.CDATA:
                    xmlStreamWriter.writeCData(reader.getText());
                    break;
                case XMLStreamConstants.END_ELEMENT:
                    xmlStreamWriter.writeEndElement();
                    break;
                case XMLStreamConstants.END_DOCUMENT:
                    xmlStreamWriter.writeEndDocument();
                    break;
                case XMLStreamConstants.SPACE:
                    break;
                case XMLStreamConstants.COMMENT:
                    xmlStreamWriter.writeComment(reader.getText());
                    break;
                case XMLStreamConstants.DTD:
                    xmlStreamWriter.writeDTD(reader.getText());
                    break;
                case XMLStreamConstants.PROCESSING_INSTRUCTION:
                    xmlStreamWriter.writeProcessingInstruction(reader.getPITarget(), reader.getPIData());
                    break;
                case XMLStreamConstants.ENTITY_REFERENCE:
                    xmlStreamWriter.writeEntityRef(reader.getLocalName());
                    break;
                default:
                    throw new OMException();
            }
        }
        xmlStreamWriter.writeEndDocument();
    }

    /**
     * Gives the StAX reader using the "Mapped" formatted input JSON String.
     * 
     * @return The XMLStreamReader according to the JSON String.
     * @throws javax.xml.stream.XMLStreamException if there is an error while making the StAX reader.
     */

    public javax.xml.stream.XMLStreamReader getReader() throws javax.xml.stream.XMLStreamException {

        Map<String, String> nsMap = new HashMap<String, String>();
        nsMap.put("", "");

        // input factory for "Mapped" convention
        MappedXMLInputFactory inputFactory = new MappedXMLInputFactory(nsMap);
        String jsonString = this.getJSONString();
        return inputFactory.createXMLStreamReader(new JSONTokener(jsonString));
    }

    // returns the json string by consuming the JSON input stream.
    protected String getJSONString() {
        return json.toString();
    }

}