RabbitMQ：RPC队列

远程过程调用

1.创建Maven项目

项目目录

2.导入rabbitmq依赖

<dependency>
  <groupId>com.rabbitmqgroupId>
  <artifactId>amqp-clientartifactId>
  <version>5.7.3version>
dependency>

3.RPC模式队列-服务器Server

/**
 * RPC模式队列-服务器
 */
public class RPCServer {
    // 队列名称
    private static final String RPC_QUEUE_NAME = "rpc_queue";

    /**
     * 计算斐波那契数列
     */
    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[] args) {
        // 创建连接工厂
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("192.168.68.152");
        factory.setPort(5672);
        factory.setUsername("lwx");
        factory.setPassword("lwx");
        factory.setVirtualHost("/lwx");

        try {
            // 通过工厂创建连接
            final Connection connection = factory.newConnection();
            // 获取信道
            final Channel channel = connection.createChannel();
            // 声明队列
            channel.queueDeclare(RPC_QUEUE_NAME, false, false, false, null);
            channel.queuePurge(RPC_QUEUE_NAME);

            /**
             * 限制RabbitMQ只发不超过1条的消息给同一消费者。
             * 当消息处理完毕后，有了反馈，才会进行第二次发送。
             */
            int prefetchCount = 1;
            channel.basicQos(prefetchCount);

            System.out.println("[x] Awaiting RPC requests");

            Object monitor = new Object();
            // 获取消息
            DeliverCallback deliverCallback = (consumerTag, delivery) -> {
                // 获取replyTo队列和correlationId请求标识
                AMQP.BasicProperties replyProps = new AMQP.BasicProperties
                        .Builder()
                        .correlationId(delivery.getProperties().getCorrelationId())
                        .build();

                String response = "";
                try {
                    // 接收客户端消息
                    String message = new String(delivery.getBody(), "UTF-8");
                    int n = Integer.parseInt(message);

                    System.out.println("[.] fib(" + message + ")");
                    // 服务端根据业务需求处理
                    response += fib(n);
                } catch (RuntimeException e) {
                    e.printStackTrace();
                } finally {
                    // 将处理结果发送至replyTo队列同时携带correlationId属性
                    channel.basicPublish("", delivery.getProperties().getReplyTo(),
                            replyProps, response.getBytes("UTF-8"));
                    // 手动回执消息
                    channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false);
                    // RabbitMq consumer worker thread notifies the RPC server owner thread
                    // RabbitMq消费者工作线程通知RPC服务器其他所有者线程运行
                    synchronized (monitor) {
                        monitor.notify();
                    }
                }
            };
            // 监听队列
            /**
             * autoAck = true 代表自动确认消息
             * autoAck = false 代表手动确认消息
             */
            boolean autoAck = false;
            channel.basicConsume(RPC_QUEUE_NAME, autoAck, deliverCallback, consumerTag -> {

            });

            // Wait and be prepared to consume the message from RPC client.
            // 线程等待并准备接收来自RPC客户端的消息。
            while (true) {
                synchronized (monitor) {
                    try {
                        monitor.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (TimeoutException e) {
            e.printStackTrace();
        }
    }
}

4.RPC模式队列-客户端Client

/**
 * RPC模式队列-客户端
 */
public class RPCClient implements AutoCloseable {

    private Connection connection;
    private Channel channel;
    // 队列名称
    private String requestQueueName = "rpc_queue";

    // 初始化连接
    public RPCClient() throws IOException, TimeoutException {
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("192.168.68.152");
        factory.setPort(5672);
        factory.setUsername("lwx");
        factory.setPassword("lwx");
        factory.setVirtualHost("/lwx");

        connection = factory.newConnection();
        channel = connection.createChannel();
    }

    public static void main(String[] args) {
        try (RPCClient fibonacciRpc = new RPCClient()) {
            for (int i = 0; i < 10; i++) {
                String i_str = Integer.toString(i);
                System.out.println("[x] Requesting fib(" + i_str + ")");
                // 请求服务器
                String response = fibonacciRpc.call(i_str);
                System.out.println("[.] Got '" + response + "'");
            }
        } catch (TimeoutException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    //请求服务端
    private String call(String message) throws IOException, InterruptedException {
        // correlationId请求标识ID
        final String corrId = UUID.randomUUID().toString();

        // 获取队列名称
        String replyQueueBame = channel.queueDeclare().getQueue();

        // 设置replyTo队列和correlationId请求标识
        AMQP.BasicProperties props = new AMQP.BasicProperties
                .Builder()
                .correlationId(corrId)
                .replyTo(replyQueueBame)
                .build();

        // 发送消息至队列
        channel.basicPublish("", requestQueueName, props, message.getBytes("UTF-8"));

        // 设置线程等待，每次只接收一个响应结果
        final BlockingQueue response = new ArrayBlockingQueue<>(1);

        // 接受服务器返回结果
        String ctag = channel.basicConsume(replyQueueBame, true, (consumerTag, delivery) -> {
            if (delivery.getProperties().getCorrelationId().equals(corrId)) {
                // 将给定的元素在给定的时间内设置到线程队列中，如果设置成功返回true，否则返回false
                response.offer(new String(delivery.getBody(), "UTF-8"));
            }
        }, consumerTag -> {
        });

        // 从线程队列中获取值，如果线程队列中没有值，线程会一直阻塞，直到线程队列中有值，并且取得该值
        String result = response.take();
        // 从消息队列中丢弃该值
        channel.basicCancel(ctag);

        return result;
    }

    // 关闭连接
    @Override
    public void close() throws Exception {
        connection.close();
    }
}

5.运行

1. 先运行服务器Server
2. 再运行客户端Client
   运行结果：