/*
    * Copyright 2006-2007 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.jms;
  
  import javax.jms.Message;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.springframework.batch.item.ItemReader;
  import org.springframework.beans.factory.InitializingBean;
  import org.springframework.jms.core.JmsOperations;
  import org.springframework.jms.core.JmsTemplate;
  import org.springframework.util.Assert;
  
  /**
   * An {@link ItemReader} for JMS using a {@link JmsTemplate}. The template
   * should have a default destination, which will be used to provide items in
   * {@link #read()}.<br/>
   * <br/>
   * 
   * The implementation is thread safe after its properties are set (normal
   * singleton behavior).
   * 
   * @author Dave Syer
   * 
   */
  public class JmsItemReader<T> implements ItemReader<T>, InitializingBean {
  
  	protected Log logger = LogFactory.getLog(getClass());
  
  	protected Class<? extends T> itemType;
  
  	protected JmsOperations jmsTemplate;
  
  	/**
  	 * Setter for jms template.
  	 * 
  	 * @param jmsTemplate a {@link JmsOperations} instance
  	 */
  	public void setJmsTemplate(JmsOperations jmsTemplate) {
  		this.jmsTemplate = jmsTemplate;
  		if (jmsTemplate instanceof JmsTemplate) {
  			JmsTemplate template = (JmsTemplate) jmsTemplate;
  			Assert.isTrue(template.getReceiveTimeout() != JmsTemplate.RECEIVE_TIMEOUT_INDEFINITE_WAIT,
  					"JmsTemplate must have a receive timeout!");
  			Assert.isTrue(template.getDefaultDestination() != null || template.getDefaultDestinationName() != null,
  					"JmsTemplate must have a defaultDestination or defaultDestinationName!");
  		}
  	}
  
  	/**
  	 * Set the expected type of incoming message payloads. Set this to
  	 * {@link Message} to receive the raw underlying message.
  	 * 
  	 * @param itemType the java class of the items to be delivered. Typically
  	 * the same as the class parameter
  	 * 
  	 * @throws IllegalStateException if the message payload is of the wrong
  	 * type.
  	 */
  	public void setItemType(Class<? extends T> itemType) {
  		this.itemType = itemType;
  	}
  
      @Override
  	@SuppressWarnings("unchecked")
  	public T read() {
  		if (itemType != null && itemType.isAssignableFrom(Message.class)) {
  			return (T) jmsTemplate.receive();
  		}
  		Object result = jmsTemplate.receiveAndConvert();
  		if (itemType != null && result != null) {
  			Assert.state(itemType.isAssignableFrom(result.getClass()),
  					"Received message payload of wrong type: expected [" + itemType + "]");
  		}
  		return (T) result;
  	}
  
      @Override
  	public void afterPropertiesSet() throws Exception {
  		Assert.notNull(this.jmsTemplate, "The 'jmsTemplate' is required.");
  	}
  }