modules/jaxws/src/org/apache/axis2/jaxws/message/util/XMLStreamReaderSplitter.java

/*
 * Copyright 2004,2005 The Apache Software Foundation.
 * Copyright 2006 International Business Machines Corp.
 *
 * 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.axis2.jaxws.message.util;


import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;

/**
 * XMLStreamReaderSplitter
 * An XMLStreamReaderSplitter wraps an existing XMLStreamReader and makes it 
 * appear that the XMLStreamReader is for a single element tree.
 * Once the element tree is consumed, the getNextReader method may be called to 
 * get the next element tree.
 * 
 * For example, suppose the input xml is the following:
 * 
 * spurious text 1
 * <data>
 *   <a>a data</a>
 *   <b>b data</b>
 * </data>
 * spurious text 2
 * <data2>
 *   <a2>a data</a2>
 *   <b2>b data</b2>
 * </data2>
 * 
 * The XMLStreamReaderSplitter will only return the events for:
 * <data>
 *   <a>a data</a>
 *   <b>b data</b>
 * </data>
 * 
 * Once these events are consumed, the nextStreamReader method can be called, which
 * will return:
 * <data2>
 *   <a2>a data</a2>
 *   <b2>b data</b2>
 * </data2>
 * 
 * Note that the spurious text and comments between the elements are ignored.
 * 
 */
public class XMLStreamReaderSplitter extends XMLStreamReaderFilter {

	int depth = 0;
	boolean start = true;
	/**
	 * Split the input reader into multiple element trees
	 * @param reader XMLStreamReader
	 */
	public XMLStreamReaderSplitter(XMLStreamReader reader) {
		super(reader);
		init();
	}
	
	/**
	 * Reset for a new element tree
	 */
	private void init() {
		depth = 0;
		start = true;
	}
	
	public int next() throws XMLStreamException {
		// If starting a new tree, ignore all of the 
		// events until the first start element is found.
		if (start) {
			start = false; 
			depth = 1;
			int event = super.next();
			
			while (event != START_ELEMENT) {
				if (event == START_ELEMENT) {
					return event;
				} else if (this.hasNext()) {
					event = super.next();
				} else {
					return event;
				}
			}	
			return event;
		} else {
			// Processing a tree.  Adjust the 
			// depth as the tags are encountered.
			if (depth == 0) {
				// Some consumers expect an END_DOCUMENT to end their processing (some consumers will trigger the end of processing using hasNext())
				return END_DOCUMENT;
			}
			int event = super.next();
			if (event == START_ELEMENT) {
				depth++;
			} else if (event == END_ELEMENT) {
				depth--;
			} 
			return event;
		}
	}
	
	@Override
	public boolean hasNext() throws XMLStreamException {
		if (depth == 0) {
			// If this element tree is consumed return false
			if (start) {
				return super.hasNext();
			} else {
				return false;
			}
		} else {
			return super.hasNext();
		}
	}

	
	/**
	 * getStreamReader
	 * @return XMLStreamReader for the next element tree.
	 * If the prior stream reader is not consumed, this method will return null.
	 * (Use hasNext() to see if the prior stream reader is consumed)
	 * @throws XMLStreamReader
	 */
	public XMLStreamReader getNextReader() throws XMLStreamException {
		if (!hasNext()) {
			init();
			if (hasNext()) {
				// Return newly initialized reader
				return this;
			} else {
				// Return null indicating no reader is available
				return null;
			}
		} else {
			// Return null if the current reader is still be read
			return null;
		}
			
	}
}