JMS&MQ,从入门到精通(六)

本篇我们来介绍一下activeMq的Queue的细节之处

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

思路

1.创建两个消费者，共同监听同一个Queue,但是它们的Selector不同
2.然后创建一个消息生产者，来发送多个消息

一个简单的实例

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: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。
* */

不知道大家看出来了没,这里有点SQL-92标准的where查询的味道;

TextMessage message = session.createTextMessage("Message" + i + ", receiver:" + receiver);
message.setStringProperty("receiver", receiver);

运行结果如下图;

下篇将结合本篇的精华之处,做一个复杂一点的实例,前方高能!!!