Java中RabbitMQ队列实现RPC详解

package com.adtec.rabbitmq;
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.DefaultConsumer;
import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Envelope;
import java.io.IOException;
import java.util.UUID;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeoutException;
public class RPCClient {
    private Connection connection;
    private Channel channel;
    private String requestQueueName = "rpc_queue";
    private String replyQueueName;
    public RPCClient() throws IOException, TimeoutException {
        //建立一个连接和一个通道，并为回调声明一个唯一的'回调'队列
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("localhost");
        connection = factory.newConnection();
        channel = connection.createChannel();
        //定义一个临时变量的接受队列名    
        replyQueueName = channel.queueDeclare().getQueue();
    }
    //发送RPC请求  
    public String call(String message) throws IOException, InterruptedException {
         //生成一个唯一的字符串作为回调队列的编号
        String corrId = UUID.randomUUID().toString();
        //发送请求消息，消息使用了两个属性：replyto和correlationId
        //服务端根据replyto返回结果，客户端根据correlationId判断响应是不是给自己的
        AMQP.BasicProperties props = new AMQP.BasicProperties.Builder().correlationId(corrId).replyTo(replyQueueName)
                .build();
        //发布一个消息，requestQueueName路由规则
        channel.basicPublish("", requestQueueName, props, message.getBytes("UTF-8"));
        //由于我们的消费者交易处理是在单独的线程中进行的，因此我们需要在响应到达之前暂停主线程。
        //这里我们创建的 容量为1的阻塞队列ArrayBlockingQueue，因为我们只需要等待一个响应。
        final BlockingQueue<String> response = new ArrayBlockingQueue<String>(1);
        // String basicConsume(String queue, boolean autoAck, Consumer callback)
        channel.basicConsume(replyQueueName, true, new DefaultConsumer(channel) {
            @Override
            public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties,
                    byte[] body) throws IOException {
                //检查它的correlationId是否是我们所要找的那个
                if (properties.getCorrelationId().equals(corrId)) {
                    //如果是，则响应BlockingQueue
                    response.offer(new String(body, "UTF-8"));
                }
            }
        });
        return response.take();
    }
    public void close() throws IOException {
        connection.close();
    }
    public static void main(String[] argv) {
        RPCClient fibonacciRpc = null;
        String response = null;
        try {
            fibonacciRpc = new RPCClient();
            System.out.println(" [x] Requesting fib(30)");
            response = fibonacciRpc.call("30");
            System.out.println(" [.] Got '" + response + "'");
        } catch (IOException | TimeoutException | InterruptedException e) {
            e.printStackTrace();
        } finally {
            if (fibonacciRpc != null) {
                try {
                    fibonacciRpc.close();
                } catch (IOException _ignore) {
                }
            }
        }
    }
}

package rabbitmq;
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Consumer;
import com.rabbitmq.client.DefaultConsumer;
import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Envelope;
import java.io.IOException;
import java.util.concurrent.TimeoutException;
public class RPCServer {
    private static final String RPC_QUEUE_NAME = "rpc_queue";
    //具体处理方法
    private static int fib(int n) {
        if (n == 0)
            return 0;
        if (n == 1)
            return 1;
        return fib(n - 1) + fib(n - 2);
    }
    public static void main(String[] argv) {
         //建立连接、通道，并声明队列 
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("localhost");
        Connection connection = null;
        try {
            connection = factory.newConnection();
            final Channel channel = connection.createChannel();
            channel.queueDeclare(RPC_QUEUE_NAME, false, false, false, null);
            channel.basicQos(1);
            System.out.println(" [x] Awaiting RPC requests");
            Consumer consumer = new DefaultConsumer(channel) {
                @Override
                public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties,
                        byte[] body) throws IOException {
                    AMQP.BasicProperties replyProps = new AMQP.BasicProperties.Builder()
                            .correlationId(properties.getCorrelationId()).build();
                    String response = "";
                    try {
                        String message = new String(body, "UTF-8");
                        int n = Integer.parseInt(message);
                        System.out.println(" [.] fib(" + message + ")");
                        response += fib(n);
                    } catch (RuntimeException e) {
                        System.out.println(" [.] " + e.toString());
                    } finally {
                        // 返回处理结果队列
                        channel.basicPublish("", properties.getReplyTo(), replyProps, response.getBytes("UTF-8"));
                        //  确认消息，已经收到后面参数 multiple：是否批量.true:将一次性确认所有小于envelope.getDeliveryTag()的消息。
                        channel.basicAck(envelope.getDeliveryTag(), false);
                        // RabbitMq consumer worker thread notifies the RPC
                        // server owner thread
                        synchronized (this) {
                            this.notify();
                        }
                    }
                }
            };
            //取消自动确认
            boolean autoAck = false ;
            channel.basicConsume(RPC_QUEUE_NAME, autoAck, consumer);
            // Wait and be prepared to consume the message from RPC client.
            while (true) {
                synchronized (consumer) {
                    try {
                        consumer.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        } catch (IOException | TimeoutException e) {
            e.printStackTrace();
        } finally {
            if (connection != null)
                try {
                    connection.close();
                } catch (IOException _ignore) {
                }
        }
    }
}