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。
package com.bijian.study; 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("tcp://localhost:61616"); 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:A ConsumerB get Message1, receiver:B ConsumerB get Message2, receiver:B ConsumerA get Message3, receiver:A ConsumerB get Message4, receiver:B ConsumerB get Message5, receiver:B ConsumerA get Message6, receiver:A ConsumerB get Message7, receiver:B ConsumerB get Message8, receiver:B ConsumerA get Message9, receiver:A
可以看出,消息消费者只会取走它自己感兴趣的消息。
文章来源:http://www.cnblogs.com/guthing/archive/2010/06/12/1757172.html
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