Message brokers are elements in telecommunication or computer networks where software applications communicate by exchanging formally-defined messages. Message brokers are a building block of message-oriented middleware.
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Setup
添加 Spring AMQP 的 Spring Boot starter 組件
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-amqp</artifactId>
</dependency>
Application Code
Create a RabbitMQ message receiver
首先我們創建一個 Receiver 去接收壞蛋出現的事件, 並讓我們的大英雄去抓住他
@Component
public class Receiver {
public void catchVillains(String villain) {
try {
// Assume hero catches the villain in 5 seconds
Thread.sleep(5000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("Catched villain<" + villain + ">");
}
}
Register the listener and send a message
RabbitMQ 消息模型的核心概念是: 消息製造者不會直接發送消息給 Queue , 而是發給一個 Exchange , Exchange 負責分發消息給一個或者多個 Queue , 所以消息製造者分本不知道消息發送給了哪個 Queue.
@Configuration
public class MQConfig {
final static String queueName = "villains-events";
@Bean
Queue queue() {
return new Queue(queueName, false);
}
@Bean
TopicExchange exchange() {
return new TopicExchange("villains-events-exchange");
}
@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.setConcurrentConsumers(2);
container.setConnectionFactory(connectionFactory);
container.setQueueNames(queueName);
container.setMessageListener(listenerAdapter);
return container;
}
@Bean
MessageListenerAdapter listenerAdapter(Receiver receiver) {
return new MessageListenerAdapter(receiver, "catchVillains");
}
}
container.setConcurrentConsumers(2);指定消息接收者同時可以處理2個消息
Spring Boot automatically creates a connection factory and a
RabbitTemplate, reducing the amount of code you have to write.
Create a message sender
使用 RabbitTemplate 發送消息給隊列
@Component
public class Sender {
private final RabbitTemplate rabbitTemplate;
public Sender(RabbitTemplate rabbitTemplate) {
this.rabbitTemplate = rabbitTemplate;
}
public void send(String message) throws Exception {
System.out.println("Sending villains events...");
rabbitTemplate.convertAndSend(MQConfig.queueName, message);
}
}
Create villains Restful API
在controller裡增加大壞蛋叫囂的方法
@Autowired
private Sender sender;
@RequestMapping(value="/villains", method=RequestMethod.POST)
String home(@RequestParam("message") String message) throws Exception {
sender.send(message);
return "Done!";
}
Test
docker run --rm --name my-rabbitmq -p 5672:5672 -p 15672:15672 rabbitmq:management
打开浏览器并访问：http://localhost:15672/，并使用默认用户guest登录，密码也为guest。
執行命令
mvn spring-boot:run
運行應用程序。
壞蛋出現了：
POST to http://localhost:8080/villains?message=I am here!
你可以在後台看到
Sending villains events...
Catched villain<I am here!>
連續發送多個消息，可以驗證大英雄可以同時處理兩個大壞蛋。
Deploy to CloudFoundry
部署到 CloudFoundry 之前我們需要創建一個 AMQP 服務，這裡我們使用 Pivotal CloudFoundry Marketplace 裡提供的 CloudAMQP 服務
cf create-service cloudamqp lemur try-cf-amqp
創建成功後，把 CloudAMQP 服務名稱加入 manifest 文件中，全部信息如下
---
applications:
- name: try-cf-message-broker
buildpack: java_buildpack
instances: 1
memory: 200M
host: try-cf-message-broker
path: target/try-cf-0.0.1-SNAPSHOT.jar
services:
- try-cf-amqp
上傳
cf push
上傳成功之後訪問鏈接即可發送消息
https://try-cf-message-broker.cfapps.io/villains?message=I am here!
可以查看 CloudFoundry 的應用後台打印信息
cf logs try-cf-message-broker
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