RabbitMQ Learning (3): Example

We have talked about the basic concepts of rabbitmq and a sample of application. Now, in this blog, we will show some working code about how to config and send/receive message. (Notice this blog is mainly composed of code, you may would like to open you IDE and type/clone code and run it along the blog).

Pure Java

If we use pure java code, we can do like following:

// set up connection
CachingConnectionFactory cf = new CachingConnectionFactory("host", 5672);
cf.setUsername("timer");
cf.setPassword("xxx");
cf.setVirtualHost("timer_host");

// set up the queue, exchange, binding on the broker
RabbitAdmin admin = new RabbitAdmin(cf);
Queue queue = new Queue("timerServer");
admin.declareQueue(queue);
TopicExchange exchange = new TopicExchange("timerExchange");
admin.declareExchange(exchange);
admin.declareBinding(BindingBuilder.bind(queue).to(exchange).with("timer.*.add"));

// set up the listener and container, which can be used to consume message
SimpleMessageListenerContainer container =
        new SimpleMessageListenerContainer(cf);

MessageListenerAdapter adapter = new MessageListenerAdapter(new Object() {
    public void handleMessage(String msg) {
        // ...
    }
});
container.setMessageListener(adapter);
container.setQueueNames("timerServer");
// start listening
container.start();

RabbitTemplate template = new RabbitTemplate(cf);
template.setExchange("timerExchange");
// use template to send message

It works, but a little bit tedious, we can do better through the help of spring.

A little bit complicated example which works with utility wrapper (which is described in last serial blog) can be found here.

Spring

Spring has the support of rabbit, we can config them using XML file:

<rabbit:connection-factory id="cf" host="host" virtual-host="timer_host" username="timer" password="xxx"/>

<rabbit:template id="rabbitTemplate" connection-factory="cf" exchange="timerExchange" routing-key="timer.announcement.add"/>

<rabbit:admin connection-factory="cf" />

<rabbit:queue name="timerClient" />

<rabbit:topic-exchange name="timerExchange">
    <rabbit:bindings>
        <rabbit:binding queue="timerClient" pattern="timer.announcement.timeout" />
    </rabbit:bindings>
</rabbit:topic-exchange>

<rabbit:listener-container connection-factory="cf">
    <rabbit:listener ref="receiver" queue-names="timerClient" method="xxx"/>
</rabbit:listener-container>


<bean id="receiver" class="x.x.EchoReceiver" />

The upper XML config is the same with Java code in functionality, but just expressed
Receiver class

public class EchoReceiver {
  public void xxx(String msg) {}
}

Now, can use Autowire rabbit template to send message, use receiver to consume message consistently.

Spring Boot

Spring Boot move back to prefer to use Java code config with annotations. Using Spring Boot can save a lot of config effort because of the help of annotations which provides many default settings:

• ConditionalOnBean
• ConditionalOnMissingBean
• ConditionalOnClass

You can view those matching process by setting logging levels of Spring Boot to be DEBUG or lower.

The following is the sample code to config a RabbitMQ consumer:

@Bean
Queue queue() {
    return new Queue(queueName, true);
}

@Bean
TopicExchange exchange() {
    return new TopicExchange("spring-boot-exchange", true, false);
}

@Bean
Binding binding(Queue queue, TopicExchange exchange) {
    return BindingBuilder.bind(queue).to(exchange).with(queueName);
}

@Bean
SimpleMessageListenerContainer container(ConnectionFactory connectionFactory,
                                         MessageListenerAdapter listenerAdapter) {
    SimpleMessageListenerContainer container = new SimpleMessageListenerContainer();
    container.setConnectionFactory(connectionFactory);
    container.setQueueNames(queueName);
    container.setMessageListener(listenerAdapter);
    container.setAcknowledgeMode(AcknowledgeMode.AUTO);
    return container;
}

@Bean
MessageListenerAdapter listenerAdapter(Receiver receiver) {
    return new MessageListenerAdapter(receiver, "receiveMessage");
}

And some properties used by Spring RabbitMQ integration to create connection:

spring.rabbitmq.host=192.168.1.100
spring.rabbitmq.virtual-host=timer_host
spring.rabbitmq.username=timer
spring.rabbitmq.password=timer

A producer is much simpler, which only needs set up the connection and the queue it want to send to. The working example of this sample can be found here.

Multiple Listener in a Single Project

In some cases, we want to consume multiple queues in the same project, which needs multiple listeners. This can be done as following configuration XML shows:

<rabbit:topic-exchange name="timerExchange">
    <rabbit:bindings>
        <rabbit:binding queue="timerClient" pattern="timer.announcement.timeout" />
        <rabbit:binding queue="testClient" pattern="timer.test.timeout" />
    </rabbit:bindings>
</rabbit:topic-exchange>

<rabbit:listener-container connection-factory="cf">
    <rabbit:listener ref="receiver" queue-names="timerClient" />
    <rabbit:listener ref="receiverTest" queue-names="testClient" />
</rabbit:listener-container>


<bean id="receiver" class="cn.superid.webapp.message.EchoReceiver" />

<!--following is for test-->

<rabbit:queue name="testClient" />

<bean id="receiverTest" class="cn.superid.webapp.message.TestReceiver" />

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