SelectXMLVariableBinding.java

/*
   This file is part of the LarKC platform 
   http://www.larkc.eu/

   Copyright 2010 LarKC project consortium

   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 eu.larkc.core.query;

import java.io.IOException;
import java.io.NotSerializableException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.List;

import org.openrdf.model.BNode;
import org.openrdf.model.Literal;
import org.openrdf.model.URI;
import org.openrdf.model.Value;
import org.openrdf.model.impl.BNodeImpl;
import org.openrdf.model.impl.LiteralImpl;
import org.openrdf.model.impl.URIImpl;
import org.openrdf.query.impl.ListBindingSet;
import org.xml.sax.Attributes;
import org.xml.sax.helpers.DefaultHandler;

public class SelectXMLVariableBinding extends VariableBindingBase {

	private DefaultHandlerHelper dh;
	private final static long serialVersionUID = 1L;

	public synchronized DefaultHandler getDefaultHandler() {
		if (dh == null) {
			dh = new DefaultHandlerHelper();
		}
		return dh;
	}

	private synchronized void notifySuper() {
		super.notifyAll();
	}

	// Custom serialization is disabled for now
	private void writeObject(ObjectOutputStream out) throws IOException {
		throw new NotSerializableException("Not implemented!");
	}

	private void readObject(ObjectInputStream in) throws IOException,
			ClassNotFoundException {
		throw new NotSerializableException("Not implemented!");
	}

	/**
	 * Helper class to mimic multiple class inheritance.
	 * 
	 * @author vassil
	 * 
	 */
	public class DefaultHandlerHelper extends DefaultHandler {

		private List<String> varNames = new ArrayList<String>();
		private String inBindName;
		private Class<?> bindType;
		private String literType;
		private Value[] values;
		private int pos;
		private StringBuffer buffer = new StringBuffer();

		public void startElement(String uri, String localName, String qname,
				Attributes attr) {
			if (qname.equals("variable")) {
				varNames.add(attr.getValue("name"));
			} else if (qname.equals("result")) {
				values = new Value[bindNames.length];
			} else if (qname.equals("binding")) {
				inBindName = attr.getValue("name");
			} else if (qname.equals("uri")) {
				bindType = URI.class;
			} else if (qname.equals("bnode")) {
				bindType = BNode.class;
			} else if (qname.equals("literal")) {
				bindType = Literal.class;
				literType = attr.getValue("datatype");
			}
		}

		public void endElement(String uri, String localName, String qname) {
			if (qname.equals("head")) {
				bindNames = varNames.toArray(new String[varNames.size()]);
				notifySuper();
			} else if (qname.equals("result")) {
				while (true) {
					try {
						results.put(new ListBindingSet(varNames, values));
						return;
					} catch (InterruptedException ie) {
					}
				}
			} else if (qname.equals("uri")) {
				values[pos] = new URIImpl(buffer.toString());
				buffer.delete(0, buffer.length());
			} else if (qname.equals("bnode")) {
				values[pos] = new BNodeImpl(buffer.toString());
				buffer.delete(0, buffer.length());
			} else if (qname.equals("literal")) {
				if (literType == null) {
					values[pos] = new LiteralImpl(buffer.toString());
				} else {
					values[pos] = new LiteralImpl(buffer.toString(),
							new URIImpl(literType));
				}
				buffer.delete(0, buffer.length());
			}
		}

		public void characters(char[] ch, int start, int length) {
			if (bindType == null) {
				return;
			}
			pos = varNames.indexOf(inBindName);
			String s = new String(ch, start, length);
			if (s.trim().length() == 0) {
				return;
			}
			buffer.append(s);
		}

		public void endDocument() {
			while (true) {
				try {
					results.put(new FinalBindingSet());
					return;
				} catch (InterruptedException ie) {
				}
			}
		}
	}
}