/*
    * Copyright 2012-2013 the original author or authors.
    *
    * 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.springframework.batch.item.amqp;
  
  import org.springframework.amqp.core.AmqpTemplate;
  import org.springframework.amqp.core.Message;
  import org.springframework.batch.item.ItemReader;
  import org.springframework.util.Assert;
  
  /**
   * <p>
   * AMQP {@link ItemReader} implementation using an {@link AmqpTemplate} to
   * receive and/or convert messages.
   * </p>
   *
   * @author Chris Schaefer
   */
  public class AmqpItemReader<T> implements ItemReader<T> {
  	private final AmqpTemplate amqpTemplate;
  	private Class<? extends T> itemType;
  
  	public AmqpItemReader(final AmqpTemplate amqpTemplate) {
  		Assert.notNull(amqpTemplate, "AmpqTemplate must not be null");
  
  		this.amqpTemplate = amqpTemplate;
  	}
  
  	@Override
  	@SuppressWarnings("unchecked")
  	public T read() {
  		if (itemType != null && itemType.isAssignableFrom(Message.class)) {
  			return (T) amqpTemplate.receive();
  		}
  
  		Object result = amqpTemplate.receiveAndConvert();
  
  		if (itemType != null && result != null) {
  			Assert.state(itemType.isAssignableFrom(result.getClass()),
  					"Received message payload of wrong type: expected [" + itemType + "]");
  		}
  
  		return (T) result;
  	}
  
  	public void setItemType(Class<? extends T> itemType) {
  		Assert.notNull(itemType, "Item type cannot be null");
  		this.itemType = itemType;
  	}
  }