深入JMS - 8 - Selector过滤
前面的例子中创建一个消息消费者使用的是:
sesssion.createConsumer(destination)
另外，还提供了另一种方式：
sesssion.createConsumer(destination, selector)
这里selector是一个字符串，用来过滤消息。也就是说，这种方式可以创建一个可以只接收特定消息的一个消费者。Selector的格式是类似于SQL-92的一种语法。可以用来比较消息头信息和属性。
下面的例子中，创建两个消费者，共同监听同一个Queue，但是它们的Selector不同，然后创建一个消息生产者，来发送多个消息。
import javax.jms.Connection;import javax.jms.JMSException;import javax.jms.Message;import javax.jms.MessageConsumer;import javax.jms.MessageListener;import javax.jms.MessageProducer;import javax.jms.Queue;import javax.jms.Session;import javax.jms.TextMessage;import org.apache.activemq.ActiveMQConnectionFactory;import org.apache.activemq.command.ActiveMQQueue;public class JMSSelectorTest { public static void main(String[] args) throws Exception { ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory("vm://localhost"); Connection connection = factory.createConnection(); connection.start(); Queue queue = new ActiveMQQueue("testQueue"); Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE); MessageConsumer comsumerA = session.createConsumer(queue, "receiver = 'A'"); comsumerA.setMessageListener(new MessageListener(){ public void onMessage(Message m) { try { System.out.println("ConsumerA get " + ((TextMessage) m).getText()); } catch (JMSException e1) { } } }); MessageConsumer comsumerB = session.createConsumer(queue, "receiver = 'B'"); comsumerB.setMessageListener(new MessageListener(){ public void onMessage(Message m) { try { System.out.println("ConsumerB get " + ((TextMessage) m).getText()); } catch (JMSException e) { } } }); MessageProducer producer = session.createProducer(queue); for(int i=0; i<10; i++) { String receiver = (i%3 == 0 ? "A" : "B"); TextMessage message = session.createTextMessage("Message" + i + ", receiver:" + receiver); message.setStringProperty("receiver", receiver); producer.send(message ); } }}结果如下：ConsumerA get Message0, receiver:AConsumerB get Message1, receiver:BConsumerB get Message2, receiver:BConsumerA get Message3, receiver:AConsumerB get Message4, receiver:BConsumerB get Message5, receiver:BConsumerA get Message6, receiver:AConsumerB get Message7, receiver:BConsumerB get Message8, receiver:BConsumerA get Message9, receiver:A