消息的消费者接收消息可以采用两种方式:
1、consumer.receive() 或 consumer.receive(int timeout);
2、注册一个MessageListener。
采用第一种方式,消息的接收者会一直等待下去,直到有消息到达,或者超时。后一种方式会注册一个监听器,当有消息到达的时候,会回调它的onMessage()方法。下面举例说明:
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MessageConsumer comsumer = session.createConsumer(queue);
comsumer.setMessageListener(new MessageListener(){
@Override
public void onMessage(Message m) {
TextMessage textMsg = (TextMessage) m;
try {
System.out.println(textMsg.getText());
} catch (JMSException e) {
e.printStackTrace();
}
}
});
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MessageConsumer comsumer = session.createConsumer(queue);
comsumer.setMessageListener(new MessageListener(){
@Override
public void onMessage(Message m) {
TextMessage textMsg = (TextMessage) m;
try {
System.out.println(textMsg.getText());
} catch (JMSException e) {
e.printStackTrace();
}
}
});
深入掌握JMS(四):实战Queue
Queue实现的是点到点模型,在下面的例子中,启动2个消费者共同监听一个Queue,然后循环给这个Queue中发送多个消息,我们依然采用ActiveMQ。
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import javax.jms.Connection;
import javax.jms.DeliveryMode;
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 QueueTest {
public staticvoid main(String[] args)throws Exception {
ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory("vm://localhost");
Connection connection = factory.createConnection();
connection.start();
//创建一个Queue
Queue queue = new ActiveMQQueue("testQueue");
//创建一个Session
Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
//注册消费者1
MessageConsumer comsumer1 = session.createConsumer(queue);
comsumer1.setMessageListener(new MessageListener(){
public void onMessage(Message m) {
try {
System.out.println("Consumer1 get " + ((TextMessage)m).getText());
} catch (JMSException e) {
e.printStackTrace();
}
}
});
//注册消费者2
MessageConsumer comsumer2 = session.createConsumer(queue);
comsumer2.setMessageListener(new MessageListener(){
public void onMessage(Message m) {
try {
System.out.println("Consumer2 get " + ((TextMessage)m).getText());
} catch (JMSException e) {
e.printStackTrace();
}
}
});
//创建一个生产者,然后发送多个消息。
MessageProducer producer = session.createProducer(queue);
for(int i=0; i<10; i++){
producer.send(session.createTextMessage("Message:" + i));
}
}
}
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import javax.jms.Connection;
import javax.jms.DeliveryMode;
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 QueueTest {
public static void main(String[] args) throws Exception {
ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory("vm://localhost");
Connection connection = factory.createConnection();
connection.start();
//创建一个Queue
Queue queue = new ActiveMQQueue("testQueue");
//创建一个Session
Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
//注册消费者1
MessageConsumer comsumer1 = session.createConsumer(queue);
comsumer1.setMessageListener(new MessageListener(){
public void onMessage(Message m) {
try {
System.out.println("Consumer1 get " + ((TextMessage)m).getText());
} catch (JMSException e) {
e.printStackTrace();
}
}
});
//注册消费者2
MessageConsumer comsumer2 = session.createConsumer(queue);
comsumer2.setMessageListener(new MessageListener(){
public void onMessage(Message m) {
try {
System.out.println("Consumer2 get " + ((TextMessage)m).getText());
} catch (JMSException e) {
e.printStackTrace();
}
}
});
//创建一个生产者,然后发送多个消息。
MessageProducer producer = session.createProducer(queue);
for(int i=0; i<10; i++){
producer.send(session.createTextMessage("Message:" + i));
}
}
}
运行这个例子会得到下面的输出结果:
[java] view plaincopy
Consumer1 get Message:0
Consumer2 get Message:1
Consumer1 get Message:2
Consumer2 get Message:3
Consumer1 get Message:4
Consumer2 get Message:5
Consumer1 get Message:6
Consumer2 get Message:7
Consumer1 get Message:8
Consumer2 get Message:9
[java] view plain copy
Consumer1 get Message:0
Consumer2 get Message:1
Consumer1 get Message:2
Consumer2 get Message:3
Consumer1 get Message:4
Consumer2 get Message:5
Consumer1 get Message:6
Consumer2 get Message:7
Consumer1 get Message:8
Consumer2 get Message:9
可以看出每个消息直被消费了一次,但是如果有多个消费者同时监听一个Queue的话,无法确定一个消息最终会被哪一个消费者消费。
与Queue不同的是,Topic实现的是发布/订阅模型,在下面的例子中,启动2个消费者共同监听一个Topic,然后循环给这个Topic中发送多个消息。
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- 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.Session;
- import javax.jms.TextMessage;
- import javax.jms.Topic;
- import org.apache.activemq.ActiveMQConnectionFactory;
- import org.apache.activemq.command.ActiveMQTopic;
-
- public class TopicTest {
- public staticvoid main(String[] args)throws Exception {
- ActiveMQConnectionFactory factory = newActiveMQConnectionFactory("vm://localhost");
-
- Connection connection = factory.createConnection();
- connection.start();
-
- //创建一个Topic
- Topic topic= new ActiveMQTopic("testTopic");
- Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
-
- //注册消费者1
- MessageConsumer comsumer1 = session.createConsumer(topic);
- comsumer1.setMessageListener(new MessageListener(){
- public void onMessage(Message m) {
- try {
- System.out.println("Consumer1 get " + ((TextMessage)m).getText());
- } catch (JMSException e) {
- e.printStackTrace();
- }
- }
- });
-
- //注册消费者2
- MessageConsumer comsumer2 = session.createConsumer(topic);
- comsumer2.setMessageListener(new MessageListener(){
- public void onMessage(Message m) {
- try {
- System.out.println("Consumer2 get " + ((TextMessage)m).getText());
- } catch (JMSException e) {
- e.printStackTrace();
- }
- }
-
- });
-
- //创建一个生产者,然后发送多个消息。
- MessageProducer producer = session.createProducer(topic);
- for(int i=0; i<10; i++){
- producer.send(session.createTextMessage("Message:" + i));
- }
- }
- }
[java] view plain copy
- 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.Session;
- import javax.jms.TextMessage;
- import javax.jms.Topic;
- import org.apache.activemq.ActiveMQConnectionFactory;
- import org.apache.activemq.command.ActiveMQTopic;
-
- public class TopicTest {
- public static void main(String[] args) throws Exception {
- ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory("vm://localhost");
-
- Connection connection = factory.createConnection();
- connection.start();
-
- //创建一个Topic
- Topic topic= new ActiveMQTopic("testTopic");
- Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
-
- //注册消费者1
- MessageConsumer comsumer1 = session.createConsumer(topic);
- comsumer1.setMessageListener(new MessageListener(){
- public void onMessage(Message m) {
- try {
- System.out.println("Consumer1 get " + ((TextMessage)m).getText());
- } catch (JMSException e) {
- e.printStackTrace();
- }
- }
- });
-
- //注册消费者2
- MessageConsumer comsumer2 = session.createConsumer(topic);
- comsumer2.setMessageListener(new MessageListener(){
- public void onMessage(Message m) {
- try {
- System.out.println("Consumer2 get " + ((TextMessage)m).getText());
- } catch (JMSException e) {
- e.printStackTrace();
- }
- }
-
- });
-
- //创建一个生产者,然后发送多个消息。
- MessageProducer producer = session.createProducer(topic);
- for(int i=0; i<10; i++){
- producer.send(session.createTextMessage("Message:" + i));
- }
- }
- }
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