package ejava.examples.jms20.jmsmechanics;
   
   import java.util.LinkedList;
   
   import javax.jms.JMSException;
   import javax.jms.Message;
   import javax.jms.MessageListener;
   
   import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * This client provides a JMSConsumer callback to process incoming messages.
   * It runs within a thread of the JMS client provider. 
   */
  public class AsyncClient implements MessageListener, MyClient {
      private static final Logger logger = LoggerFactory.getLogger(AsyncClient.class);
      private int count=0;
      private LinkedList<Message> messages = new LinkedList<>();
      
      public void onMessage(Message message) {
          try {
              String level = message.getStringProperty("level");            
              logger.debug("onMessage received ({}, mode={}, pri={}{}):{}", ++count,
                      message.getJMSDeliveryMode(),
                      message.getJMSPriority(),
                      (level==null?"":", level="+level),
                      message.getJMSMessageID());
              message.acknowledge();
              synchronized(messages) {
                  messages.add(message);
              }
          } catch (JMSException ex) {
              logger.error("error handling message", ex);
          }
      }
      
      public int getCount() { return count; }
      
      public Message getMessage() {
          synchronized(messages) {
              return (messages.isEmpty() ? null : messages.remove());
          }
      }
  }