JMS - ActiveMQ的简单使用

首先需要下载ActiveMQ，下面的链接给我们列出了所有版本：
http://activemq.apache.org/download-archives.html
每个版本为不同的OS提供了链接：

公司电脑是windows的，用目录下的activemq.bat启动：

端口号默认是61616，可以在conf/activemq.xml中看到:

<transportConnectors>
    <!-- DOS protection, limit concurrent connections to 1000 and frame size to 100MB -->
    <transportConnector name="openwire" uri="tcp://0.0.0.0:61616?maximumConnections=1000&amp;wireFormat.maxFrameSize=104857600"/>
    <transportConnector name="amqp" uri="amqp://0.0.0.0:5672?maximumConnections=1000&amp;wireFormat.maxFrameSize=104857600"/>
    <transportConnector name="stomp" uri="stomp://0.0.0.0:61613?maximumConnections=1000&amp;wireFormat.maxFrameSize=104857600"/>
    <transportConnector name="mqtt" uri="mqtt://0.0.0.0:1883?maximumConnections=1000&amp;wireFormat.maxFrameSize=104857600"/>
    <transportConnector name="ws" uri="ws://0.0.0.0:61614?maximumConnections=1000&amp;wireFormat.maxFrameSize=104857600"/>
</transportConnectors>

相关的Maven dependency：

<dependency>
    <groupId>javax.jms</groupId>
    <artifactId>javax.jms-api</artifactId>
    <version>2.0</version>
</dependency>
<dependency>
    <groupId>org.apache.activemq</groupId>
    <artifactId>activemq-core</artifactId>
    <version>5.7.0</version>
</dependency>

使用javax.jms.Session跟JMS Provider通信:

ConnectionFactory connectionFactory = new ActiveMQConnectionFactory(
        ActiveMQConnection.DEFAULT_USER,
        ActiveMQConnection.DEFAULT_PASSWORD, "tcp://localhost:61616");

Connection connection = connectionFactory.createConnection();
connection.start();

Session session = connection.createSession(Boolean.TRUE,
        Session.AUTO_ACKNOWLEDGE);

然后一些目的地、发送者、发送内容什么的都是由session来弄的：

Destination destination = session.createQueue("this is sparta!!");

MessageProducer producer = session.createProducer(destination);

TextMessage message0 = session.createTextMessage("这是斯巴达!!!");
TextMessage message1 = session.createTextMessage("这也是斯巴达!!!");
TextMessage message2 = session.createTextMessage("这些都是斯巴达!!!");

producer.send(message0);
producer.send(message1);
producer.send(message2);

session.commit();

有了producer，相应地也有consumer，接收消息方法如下：

MessageConsumer consumer = session.createConsumer(destination);
System.out.println(((TextMessage) consumer.receive(10000)).getText());

结果还是consumer去一个个receive了，就像是接收人亲自去确认那样。
或许我们可以让Listener代劳:

consumer.setMessageListener(new MessageListener() {
    public void onMessage(Message message) {
        try {
            System.out.println("listener catched:::"+((TextMessage)message).getText());
        } catch (JMSException e) {
            e.printStackTrace();
        }
    }
});

当这个consumer设置了Listener的时候就不能再以receive()的方式接收了,
不然会出现javax.jms.IllegalStateException:Cannot synchronously receive a message when a MessageListener is set

如果想使用publish/subscribe，直接将createQueue改为createTopic即可，但需要理解Topic是无状态的。

完整code如下，发送者：

{
        ConnectionFactory connectionFactory = new ActiveMQConnectionFactory(
                ActiveMQConnection.DEFAULT_USER,
                ActiveMQConnection.DEFAULT_PASSWORD, "tcp://localhost:61616");
        Connection connection = connectionFactory.createConnection();
        connection.start();

        Session session = connection.createSession(Boolean.TRUE,
                Session.AUTO_ACKNOWLEDGE);

        Destination destination = session.createQueue("this is sparta!!");

        MessageProducer producer = session.createProducer(destination);
        TextMessage message0 = session.createTextMessage("这是斯巴达!!!");
        TextMessage message1 = session.createTextMessage("这也是斯巴达!!!");
        TextMessage message2 = session.createTextMessage("这些都是斯巴达!!!");
        producer.send(message0);
        producer.send(message1);
        producer.send(message2);

        session.commit();
    }

接收者：

{
        ConnectionFactory connectionFactory = new ActiveMQConnectionFactory(
                ActiveMQConnection.DEFAULT_USER,
                ActiveMQConnection.DEFAULT_PASSWORD, "tcp://localhost:61616");;
        Connection connection = connectionFactory.createConnection();
        connection.start();

        Session session = connection.createSession(Boolean.FALSE,
                Session.AUTO_ACKNOWLEDGE);

        Destination destination = session.createQueue("this is sparta!!");
        MessageConsumer consumer = session.createConsumer(destination);
        System.out.println(((TextMessage) consumer.receive(10000)).getText());
        System.out.println(((TextMessage) consumer.receive(10000)).getText());
        System.out.println(((TextMessage) consumer.receive(10000)).getText());
    }