ProtobufMessageBodyProducer.java

/*
 * Copyright 2010 The Apache Software Foundation
 *
 * 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.hadoop.hbase.rest.provider.producer;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;

import javax.ws.rs.Produces;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.ext.MessageBodyWriter;
import javax.ws.rs.ext.Provider;

import org.apache.hadoop.hbase.rest.Constants;
import org.apache.hadoop.hbase.rest.ProtobufMessageHandler;

/**
 * An adapter between Jersey and ProtobufMessageHandler implementors. Hooks up
 * protobuf output producing methods to the Jersey content handling framework.
 * Jersey will first call getSize() to learn the number of bytes that will be
 * sent, then writeTo to perform the actual I/O.
 */
@Provider
@Produces(Constants.MIMETYPE_PROTOBUF)
public class ProtobufMessageBodyProducer
  implements MessageBodyWriter<ProtobufMessageHandler> {

  private ThreadLocal<byte[]> buffer = new ThreadLocal<byte[]>();

	@Override
	public boolean isWriteable(Class<?> type, Type genericType, 
	  Annotation[] annotations, MediaType mediaType) {
      return ProtobufMessageHandler.class.isAssignableFrom(type);
  }

	@Override
	public long getSize(ProtobufMessageHandler m, Class<?> type, Type genericType,
	    Annotation[] annotations, MediaType mediaType) {
	  ByteArrayOutputStream baos = new ByteArrayOutputStream();
	  try {
	    baos.write(m.createProtobufOutput());
	  } catch (IOException e) {
	    return -1;
	  }
	  byte[] bytes = baos.toByteArray();
	  buffer.set(bytes);
	  return bytes.length;
	}

	public void writeTo(ProtobufMessageHandler m, Class<?> type, Type genericType,
	    Annotation[] annotations, MediaType mediaType, 
	    MultivaluedMap<String, Object> httpHeaders, OutputStream entityStream) 
	    throws IOException, WebApplicationException {
    byte[] bytes = buffer.get();
	  entityStream.write(bytes);
    buffer.remove();
	}
}