Java学习——rabbitmq(rpc)

 

RPC

 

/* Routing Model
         /->(Request repQueue=123 cid=abc) [...](request Queue)   \
RPCClient                                                            RPCServer
         <-\(Reply correlation_id=abc)     [...](reply Queue:123) /
*/

远程过程调用的应用场景也很广，我们来看看如何用rabbitmq实现rpc编程

 

RemoteService rs = new RemoteService();
String result = rs.speak("2012"); //block until the answer is received
System.out.println("Goodbye " + result);

关于RPC的一点看法，尽管它是一种常用的编程模型，却饱受批评，开发人员没法知道自己调用的程序是本地程序还是远程程序，可能会造成很多困惑，增加调试的复杂程度。（可以考虑使用异步流水线替代阻塞调用）

callback queue

客户端将消息和响应队列信息一并发给服务器端

 

RPCClient.java

 

package test;

import java.io.IOException;

import com.rabbitmq.client.AMQP.BasicProperties;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.ConsumerCancelledException;
import com.rabbitmq.client.QueueingConsumer;
import com.rabbitmq.client.ShutdownSignalException;

public class RPCClient {

	private Connection connection;
	private Channel channel;
	
	public RPCClient() throws IOException{
		// 创建一个连接连接服务器
		ConnectionFactory factory = new ConnectionFactory();
		factory.setHost("localhost");
		connection = factory.newConnection();
		channel = connection.createChannel();
	}
	
	public void close() throws IOException{
		channel.close();
		connection.close();	
	}
	
	public String call(String message) throws IOException, ShutdownSignalException, ConsumerCancelledException, InterruptedException {
		
		String response;
		String replyQueueName = channel.queueDeclare().getQueue();
		QueueingConsumer consumer = new QueueingConsumer(channel);
		channel.basicConsume(replyQueueName, true, consumer);
		
		String corrId = java.util.UUID.randomUUID().toString();
		
		BasicProperties props = new BasicProperties.Builder().correlationId(corrId).replyTo(replyQueueName).build();
		
		channel.basicPublish("", "request_queue", props, message.getBytes());
		
		while(true){
			QueueingConsumer.Delivery  delivery = consumer.nextDelivery();
			if(delivery.getProperties().getCorrelationId().equals(corrId)){
				response = new String(delivery.getBody());
				break;
			}
		}
		return response;
	}
	
	public static void main(String[] args) throws IOException, ShutdownSignalException, ConsumerCancelledException, InterruptedException {
			RPCClient client = new RPCClient();
			String res = new String(client.call("test"));
			System.out.println(res);
			client.close();
	}
}

RPCServer.java

 

package test;

import java.io.IOException;

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.ConsumerCancelledException;
import com.rabbitmq.client.QueueingConsumer;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.ShutdownSignalException;
import com.rabbitmq.client.AMQP.BasicProperties;

public class RPCServer {

	public static void main(String[] args) throws IOException, ShutdownSignalException, ConsumerCancelledException, InterruptedException {
		// 创建一个连接接收数据
		ConnectionFactory factory = new ConnectionFactory();
		factory.setHost("localhost");
		Connection connection = factory.newConnection();
		Channel channel = connection.createChannel();
		
		channel.queueDeclare("request_queue", false, false, false, null);
		channel.basicQos(1);
		
		QueueingConsumer consumer = new QueueingConsumer(channel);
		channel.basicConsume("request_queue", false, consumer);
		while(true){
			QueueingConsumer.Delivery delivery = consumer.nextDelivery();
			
			BasicProperties props = delivery.getProperties();
			BasicProperties replyProps = new BasicProperties.Builder().correlationId(props.getCorrelationId()).replyTo(props.getCorrelationId()).build();
			String response = new String("Hello" + new String(delivery.getBody()));
			channel.basicPublish("", props.getReplyTo(), replyProps, response.getBytes());
			channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false);
		}
	}
}

分别运行RPCClient和RPCServer，可以得到结果hellotest