# XMLMultipleEventWriter.java

    /*
     * Copyright 2011, 2012 Odysseus Software GmbH
     *
     * Licensed 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.synapse.commons.staxon.core.json.util;

    import javax.xml.namespace.QName;
    import javax.xml.stream.XMLEventReader;
    import javax.xml.stream.XMLEventWriter;
    import javax.xml.stream.XMLStreamConstants;
    import javax.xml.stream.XMLStreamException;
    import javax.xml.stream.events.XMLEvent;

    import org.apache.synapse.commons.staxon.core.util.EventWriterDelegate;

    /**
     * <p>Simple delegate writer which generates <code>&lt;?xml-multiple?></code>
     * processing instructions when writing a sequence of elements matching some
     * element path. Use this class to trigger JSON array start events like this:
     * <pre>
     * XMLOutputFactory factory = new JsonXMLOutputFactory();
     * XMLEventWriter writer = factory.createXMLEventWriter(...);
     * writer = new XMLMultipleEventWriter(writer, false, "/alice/bob", ...);
     * </pre>
     */
    public class XMLMultipleEventWriter extends EventWriterDelegate {
        private final XMLMultipleProcessingInstructionHandler handler;

        /**
         * Create instance.
         *
         * @param parent        delegate
         * @param matchRoot     whether the root element is included in paths
         * @param multiplePaths added via {@link #addMultiplePath(String)}
         */
        public XMLMultipleEventWriter(XMLEventWriter parent, boolean matchRoot, String... multiplePaths) throws XMLStreamException {
            super(parent);

            this.handler = new XMLMultipleProcessingInstructionHandler(this, matchRoot, false);
            for (String path : multiplePaths) {
                addMultiplePath(path);
            }
        }

        @Override
        public void setParent(XMLEventWriter parent) {
            throw new UnsupportedOperationException();
        }

        /**
         * Add path to trigger <code>&lt;?xml-multiple?></code> PI.
         * The path may start with <code>'/'</code> and contain local element
         * names, separated by <code>'/'</code>, e.g
         * <code>"/foo/bar"</code>, <code>"foo/bar"</code> or <code>"bar"</code>.
         *
         * @param path multiple path
         * @throws XMLStreamException if the path is invalid
         */
        public void addMultiplePath(String path) throws XMLStreamException {
            handler.addMultiplePath(path);
        }

        @Override
        public void add(XMLEventReader reader) throws XMLStreamException {
            while (reader.hasNext()) {
                add(reader.nextEvent());
            }
        }

        @Override
        public void add(XMLEvent event) throws XMLStreamException {
            switch (event.getEventType()) {
                case XMLStreamConstants.START_ELEMENT:
                    QName name = event.asStartElement().getName();
                    handler.preStartElement(name.getPrefix(), name.getLocalPart());
                    super.add(event);
                    handler.postStartElement();
                    break;
                case XMLStreamConstants.END_ELEMENT:
                    handler.preEndElement();
                    super.add(event);
                    handler.postEndElement();
                    break;
                default:
                    super.add(event);
            }
        }
    }