⼗⼀. ⽹络通信协议设计

定义 Request / Response

/*
 * 表示一个网络通信中的请求对象. 按照自定义协议的格式来展开的
 */
public class Request {
    private int type;
    private int length;
    private byte[] payload;

    public int getType() {
        return type;
    }

    public void setType(int type) {
        this.type = type;
    }

    public int getLength() {
        return length;
    }

    public void setLength(int length) {
        this.length = length;
    }

    public byte[] getPayload() {
        return payload;
    }

    public void setPayload(byte[] payload) {
        this.payload = payload;
    }
}

/*
 * 这个对象表示一个响应. 也是根据自定义应用层协议来的
 */
public class Response {
    private int type;
    private int length;
    private byte[] payload;

    public int getType() {
        return type;
    }

    public void setType(int type) {
        this.type = type;
    }

    public int getLength() {
        return length;
    }

    public void setLength(int length) {
        this.length = length;
    }

    public byte[] getPayload() {
        return payload;
    }

    public void setPayload(byte[] payload) {
        this.payload = payload;
    }
}

定义参数⽗类

构造⼀个类表⽰⽅法的参数, 作为 Request 的 payload.
不同的⽅法中, 参数形态各异, 但是有些信息是通⽤的, 使⽤⼀个⽗类表⽰出来. 具体每个⽅法的参数再通过继承的⽅式体现

/*
 * 使用这个类表示方法的公共参数/辅助的字段.
 * 后续每个方法又会有一些不同的参数, 不同的参数再分别使用不同的子类来表示.
 */
public class BasicArguments implements Serializable {
    // 表示一次请求/响应 的身份标识. 可以把请求和响应对上.
    protected String rid;
    // 这次通信使用的 channel 的身份标识.
    protected String channelId;

    public String getRid() {
        return rid;
    }

    public void setRid(String rid) {
        this.rid = rid;
    }

    public String getChannelId() {
        return channelId;
    }

    public void setChannelId(String channelId) {
        this.channelId = channelId;
    }
}

此处的 rid 和 channelId 都是基于 UUID 来⽣成的. rid ⽤来标识⼀个请求-响应. 这⼀点在请求响应⽐较多的时候⾮常重要

定义返回值⽗类

public class BasicAckArguments extends BasicArguments implements Serializable {
    private String queueName;
    private String messageId;

    public String getQueueName() {
        return queueName;
    }

    public void setQueueName(String queueName) {
        this.queueName = queueName;
    }

    public String getMessageId() {
        return messageId;
    }

    public void setMessageId(String messageId) {
        this.messageId = messageId;
    }
}

定义其他参数类

针对每个 VirtualHost 提供的⽅法, 都需要有⼀个类表⽰对应的参数

1) ExchangeDeclareArguments

package com.example.mq.common;

import com.example.mq.mqserver.core.ExchangeType;

import java.io.Serializable;
import java.util.Map;

public class ExchangeDeclareArguments extends BasicArguments implements Serializable {
    private String exchangeName;
    private ExchangeType exchangeType;
    private boolean durable;
    private boolean autoDelete;
    private Map<String, Object> arguments;

    public String getExchangeName() {
        return exchangeName;
    }

    public void setExchangeName(String exchangeName) {
        this.exchangeName = exchangeName;
    }

    public ExchangeType getExchangeType() {
        return exchangeType;
    }

    public void setExchangeType(ExchangeType exchangeType) {
        this.exchangeType = exchangeType;
    }

    public boolean isDurable() {
        return durable;
    }

    public void setDurable(boolean durable) {
        this.durable = durable;
    }

    public boolean isAutoDelete() {
        return autoDelete;
    }

    public void setAutoDelete(boolean autoDelete) {
        this.autoDelete = autoDelete;
    }

    public Map<String, Object> getArguments() {
        return arguments;
    }

    public void setArguments(Map<String, Object> arguments) {
        this.arguments = arguments;
    }
}

⼀个创建交换机的请求, 形如:
• 可以把 ExchangeDeclareArguments 转成 byte[], 就得到了下列图⽚的结构.
• 按照 length ⻓度读取出 payload, 就可以把读到的⼆进制数据转换成ExchangeDeclareArguments 对象

2) ExchangeDeleteArguments

public class ExchangeDeleteArguments extends BasicArguments implements Serializable {
    private String exchangeName;

    public String getExchangeName() {
        return exchangeName;
    }

    public void setExchangeName(String exchangeName) {
        this.exchangeName = exchangeName;
    }
}

3) QueueDeclareArguments

public class QueueDeclareArguments extends BasicArguments implements Serializable {
    private String queueName;
    private boolean durable;
    private boolean exclusive;
    private boolean autoDelete;
    private Map<String, Object> arguments;

    public String getQueueName() {
        return queueName;
    }

    public void setQueueName(String queueName) {
        this.queueName = queueName;
    }

    public boolean isDurable() {
        return durable;
    }

    public void setDurable(boolean durable) {
        this.durable = durable;
    }

    public boolean isExclusive() {
        return exclusive;
    }

    public void setExclusive(boolean exclusive) {
        this.exclusive = exclusive;
    }

    public boolean isAutoDelete() {
        return autoDelete;
    }

    public void setAutoDelete(boolean autoDelete) {
        this.autoDelete = autoDelete;
    }

    public Map<String, Object> getArguments() {
        return arguments;
    }

    public void setArguments(Map<String, Object> arguments) {
        this.arguments = arguments;
    }
}

4) QueueDeleteArguments

public class QueueDeleteArguments extends BasicArguments implements Serializable {
    private String queueName;

    public String getQueueName() {
        return queueName;
    }

    public void setQueueName(String queueName) {
        this.queueName = queueName;
    }
}

5) QueueBindArguments

public class QueueBindArguments extends BasicArguments implements Serializable {
    private String queueName;
    private String exchangeName;
    private String bindingKey;

    public String getQueueName() {
        return queueName;
    }

    public void setQueueName(String queueName) {
        this.queueName = queueName;
    }

    public String getExchangeName() {
        return exchangeName;
    }

    public void setExchangeName(String exchangeName) {
        this.exchangeName = exchangeName;
    }

    public String getBindingKey() {
        return bindingKey;
    }

    public void setBindingKey(String bindingKey) {
        this.bindingKey = bindingKey;
    }
}

6) QueueUnbindArguments

public class QueueUnbindArguments extends BasicArguments implements Serializable {
    private String queueName;
    private String exchangeName;

    public String getQueueName() {
        return queueName;
    }

    public void setQueueName(String queueName) {
        this.queueName = queueName;
    }

    public String getExchangeName() {
        return exchangeName;
    }

    public void setExchangeName(String exchangeName) {
        this.exchangeName = exchangeName;
    }
}

7) BasicPublishArguments

public class BasicPublishArguments extends BasicArguments implements Serializable {
    private String exchangeName;
    private String routingKey;
    private BasicProperties basicProperties;
    private byte[] body;

    public String getExchangeName() {
        return exchangeName;
    }

    public void setExchangeName(String exchangeName) {
        this.exchangeName = exchangeName;
    }

    public String getRoutingKey() {
        return routingKey;
    }

    public void setRoutingKey(String routingKey) {
        this.routingKey = routingKey;
    }

    public BasicProperties getBasicProperties() {
        return basicProperties;
    }

    public void setBasicProperties(BasicProperties basicProperties) {
        this.basicProperties = basicProperties;
    }

    public byte[] getBody() {
        return body;
    }

    public void setBody(byte[] body) {
        this.body = body;
    }
}

8) BasicConsumeArguments

public class BasicConsumeArguments extends BasicArguments implements Serializable {
    private String consumerTag;
    private String queueName;
    private boolean autoAck;
    // 这个类对应的 basicConsume 方法中, 还有一个参数, 是回调函数. (如何来处理消息)
    // 这个回调函数, 是不能通过网络传输的.
    // 站在 broker server 这边, 针对消息的处理回调, 其实是统一的. (把消息返回给客户端)
    // 客户端这边收到消息之后, 再在客户端自己这边执行一个用户自定义的回调就行了.
    // 此时, 客户端也就不需要把自身的回调告诉给服务器了.
    // 这个类就不需要 consumer 成员了.


    public String getConsumerTag() {
        return consumerTag;
    }

    public void setConsumerTag(String consumerTag) {
        this.consumerTag = consumerTag;
    }

    public String getQueueName() {
        return queueName;
    }

    public void setQueueName(String queueName) {
        this.queueName = queueName;
    }

    public boolean isAutoAck() {
        return autoAck;
    }

    public void setAutoAck(boolean autoAck) {
        this.autoAck = autoAck;
    }
}

9) SubScribeReturns

public class SubScribeReturns extends BasicReturns implements Serializable {
    private String consumerTag;
    private BasicProperties basicProperties;
    private byte[] body;

    public String getConsumerTag() {
        return consumerTag;
    }

    public void setConsumerTag(String consumerTag) {
        this.consumerTag = consumerTag;
    }

    public BasicProperties getBasicProperties() {
        return basicProperties;
    }

    public void setBasicProperties(BasicProperties basicProperties) {
        this.basicProperties = basicProperties;
    }

    public byte[] getBody() {
        return body;
    }

    public void setBody(byte[] body) {
        this.body = body;
    }
}

⼗⼆. 实现 BrokerServer

创建 BrokerServer 类

• virtualHost 表⽰服务器持有的虚拟主机. 队列, 交换机, 绑定, 消息都是通过虚拟主机管理.
• sessions ⽤来管理所有的客⼾端的连接. 记录每个客⼾端的 socket.
• serverSocket 是服务器⾃⾝的 socket
• executorService 这个线程池⽤来处理响应.
• runnable 这个标志位⽤来控制服务器的运⾏停⽌.

/*
 * 这个 BrokerServer 就是咱们 消息队列 本体服务器.
 * 本质上就是一个 TCP 的服务器.
 */
public class BrokerServer {
    private ServerSocket serverSocket = null;

    // 当前考虑一个 BrokerServer 上只有一个 虚拟主机
    private VirtualHost virtualHost = new VirtualHost("default");
    // 使用这个 哈希表 表示当前的所有会话(也就是说有哪些客户端正在和咱们的服务器进行通信)
    // 此处的 key 是 channelId, value 为对应的 Socket 对象
    private ConcurrentHashMap<String, Socket> sessions = new ConcurrentHashMap<String, Socket>();
    // 引入一个线程池, 来处理多个客户端的请求.
    private ExecutorService executorService = null;
    // 引入一个 boolean 变量控制服务器是否继续运行
    private volatile boolean runnable = true;

    public BrokerServer(int port) throws IOException {
        serverSocket = new ServerSocket(port);
    }

    public void start() throws IOException {
        System.out.println("[BrokerServer] 启动!");
        executorService = Executors.newCachedThreadPool();
        try {
            while (runnable) {
                Socket clientSocket = serverSocket.accept();
                // 把处理连接的逻辑丢给这个线程池.
                executorService.submit(() -> {
                    processConnection(clientSocket);
                });
            }
        } catch (SocketException e) {
            System.out.println("[BrokerServer] 服务器停止运行!");
            // e.printStackTrace();
        }
    }

    // 一般来说停止服务器, 就是直接 kill 掉对应进程就行了.
    // 此处还是搞一个单独的停止方法. 主要是用于后续的单元测试.
    public void stop() throws IOException {
        runnable = false;
        // 把线程池中的任务都放弃了. 让线程都销毁.
        executorService.shutdownNow();
        serverSocket.close();
    }

    // 通过这个方法, 来处理一个客户端的连接.
    // 在这一个连接中, 可能会涉及到多个请求和响应.
    private void processConnection(Socket clientSocket) {
        try (InputStream inputStream = clientSocket.getInputStream();
             OutputStream outputStream = clientSocket.getOutputStream()) {
            // 这里需要按照特定格式来读取并解析. 此时就需要用到 DataInputStream 和 DataOutputStream
            try (DataInputStream dataInputStream = new DataInputStream(inputStream);
                 DataOutputStream dataOutputStream = new DataOutputStream(outputStream)) {
                while (true) {
                    // 1. 读取请求并解析.
                    Request request = readRequest(dataInputStream);
                    // 2. 根据请求计算响应
                    Response response = process(request, clientSocket);
                    // 3. 把响应写回给客户端
                    writeResponse(dataOutputStream, response);
                }
            }
        } catch (EOFException | SocketException e) {
            // 对于这个代码, DataInputStream 如果读到 EOF , 就会抛出一个 EOFException 异常.
            // 需要借助这个异常来结束循环
            System.out.println("[BrokerServer] connection 关闭! 客户端的地址: " + clientSocket.getInetAddress().toString()
                    + ":" + clientSocket.getPort());
        } catch (IOException | ClassNotFoundException | MqException e) {
            System.out.println("[BrokerServer] connection 出现异常!");
            e.printStackTrace();
        } finally {
            try {
                // 当连接处理完了, 就需要记得关闭 socket
                clientSocket.close();
                // 一个 TCP 连接中, 可能包含多个 channel. 需要把当前这个 socket 对应的所有 channel 也顺便清理掉.
                clearClosedSession(clientSocket);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private Request readRequest(DataInputStream dataInputStream) throws IOException {
        Request request = new Request();
        request.setType(dataInputStream.readInt());
        request.setLength(dataInputStream.readInt());
        byte[] payload = new byte[request.getLength()];
        int n = dataInputStream.read(payload);
        if (n != request.getLength()) {
            throw new IOException("读取请求格式出错!");
        }
        request.setPayload(payload);
        return request;
    }

    private void writeResponse(DataOutputStream dataOutputStream, Response response) throws IOException {
        dataOutputStream.writeInt(response.getType());
        dataOutputStream.writeInt(response.getLength());
        dataOutputStream.write(response.getPayload());
        // 这个刷新缓冲区也是重要的操作!!
        dataOutputStream.flush();
    }

    private Response process(Request request, Socket clientSocket) throws IOException, ClassNotFoundException, MqException {
        // 1. 把 request 中的 payload 做一个初步的解析.
        BasicArguments basicArguments = (BasicArguments) BinaryTool.fromBytes(request.getPayload());
        System.out.println("[Request] rid=" + basicArguments.getRid() + ", channelId=" + basicArguments.getChannelId()
            + ", type=" + request.getType() + ", length=" + request.getLength());
        // 2. 根据 type 的值, 来进一步区分接下来这次请求要干啥.
        boolean ok = true;
        if (request.getType() == 0x1) {
            // 创建 channel
            sessions.put(basicArguments.getChannelId(), clientSocket);
            System.out.println("[BrokerServer] 创建 channel 完成! channelId=" + basicArguments.getChannelId());
        } else if (request.getType() == 0x2) {
            // 销毁 channel
            sessions.remove(basicArguments.getChannelId());
            System.out.println("[BrokerServer] 销毁 channel 完成! channelId=" + basicArguments.getChannelId());
        } else if (request.getType() == 0x3) {
            // 创建交换机. 此时 payload 就是 ExchangeDeclareArguments 对象了.
            ExchangeDeclareArguments arguments = (ExchangeDeclareArguments) basicArguments;
            ok = virtualHost.exchangeDeclare(arguments.getExchangeName(), arguments.getExchangeType(),
                    arguments.isDurable(), arguments.isAutoDelete(), arguments.getArguments());
        } else if (request.getType() == 0x4) {
            ExchangeDeleteArguments arguments = (ExchangeDeleteArguments) basicArguments;
            ok = virtualHost.exchangeDelete(arguments.getExchangeName());
        } else if (request.getType() == 0x5) {
            QueueDeclareArguments arguments = (QueueDeclareArguments) basicArguments;
            ok = virtualHost.queueDeclare(arguments.getQueueName(), arguments.isDurable(),
                    arguments.isExclusive(), arguments.isAutoDelete(), arguments.getArguments());
        } else if (request.getType() == 0x6) {
            QueueDeleteArguments arguments = (QueueDeleteArguments) basicArguments;
            ok = virtualHost.queueDelete((arguments.getQueueName()));
        } else if (request.getType() == 0x7) {
            QueueBindArguments arguments = (QueueBindArguments) basicArguments;
            ok = virtualHost.queueBind(arguments.getQueueName(), arguments.getExchangeName(), arguments.getBindingKey());
        } else if (request.getType() == 0x8) {
            QueueUnbindArguments arguments = (QueueUnbindArguments) basicArguments;
            ok = virtualHost.queueUnbind(arguments.getQueueName(), arguments.getExchangeName());
        } else if (request.getType() == 0x9) {
            BasicPublishArguments arguments = (BasicPublishArguments) basicArguments;
            ok = virtualHost.basicPublish(arguments.getExchangeName(), arguments.getRoutingKey(),
                    arguments.getBasicProperties(), arguments.getBody());
        } else if (request.getType() == 0xa) {
            BasicConsumeArguments arguments = (BasicConsumeArguments) basicArguments;
            ok = virtualHost.basicConsume(arguments.getConsumerTag(), arguments.getQueueName(), arguments.isAutoAck(),
                    new Consumer() {
                        // 这个回调函数要做的工作, 就是把服务器收到的消息可以直接推送回对应的消费者客户端
                        @Override
                        public void handleDelivery(String consumerTag, BasicProperties basicProperties, byte[] body) throws MqException, IOException {
                            // 先知道当前这个收到的消息, 要发给哪个客户端.
                            // 此处 consumerTag 其实是 channelId. 根据 channelId 去 sessions 中查询, 就可以得到对应的
                            // socket 对象了, 从而可以往里面发送数据了
                            // 1. 根据 channelId 找到 socket 对象
                            Socket clientSocket = sessions.get(consumerTag);
                            if (clientSocket == null || clientSocket.isClosed()) {
                                throw new MqException("[BrokerServer] 订阅消息的客户端已经关闭!");
                            }
                            // 2. 构造响应数据
                            SubScribeReturns subScribeReturns = new SubScribeReturns();
                            subScribeReturns.setChannelId(consumerTag);
                            subScribeReturns.setRid(""); // 由于这里只有响应, 没有请求, 不需要去对应. rid 暂时不需要.
                            subScribeReturns.setOk(true);
                            subScribeReturns.setConsumerTag(consumerTag);
                            subScribeReturns.setBasicProperties(basicProperties);
                            subScribeReturns.setBody(body);
                            byte[] payload = BinaryTool.toBytes(subScribeReturns);
                            Response response = new Response();
                            // 0xc 表示服务器给消费者客户端推送的消息数据.
                            response.setType(0xc);
                            // response 的 payload 就是一个 SubScribeReturns
                            response.setLength(payload.length);
                            response.setPayload(payload);
                            // 3. 把数据写回给客户端.
                            //    注意! 此处的 dataOutputStream 这个对象不能 close !!!
                            //    如果 把 dataOutputStream 关闭, 就会直接把 clientSocket 里的 outputStream 也关了.
                            //    此时就无法继续往 socket 中写入后续数据了.
                            DataOutputStream dataOutputStream = new DataOutputStream(clientSocket.getOutputStream());
                            writeResponse(dataOutputStream, response);
                        }
                    });
        } else if (request.getType() == 0xb) {
            // 调用 basicAck 确认消息.
            BasicAckArguments arguments = (BasicAckArguments) basicArguments;
            ok = virtualHost.basicAck(arguments.getQueueName(), arguments.getMessageId());
        } else {
            // 当前的 type 是非法的.
            throw new MqException("[BrokerServer] 未知的 type! type=" + request.getType());
        }
        // 3. 构造响应
        BasicReturns basicReturns = new BasicReturns();
        basicReturns.setChannelId(basicArguments.getChannelId());
        basicReturns.setRid(basicArguments.getRid());
        basicReturns.setOk(ok);
        byte[] payload = BinaryTool.toBytes(basicReturns);
        Response response = new Response();
        response.setType(request.getType());
        response.setLength(payload.length);
        response.setPayload(payload);
        System.out.println("[Response] rid=" + basicReturns.getRid() + ", channelId=" + basicReturns.getChannelId()
            + ", type=" + response.getType() + ", length=" + response.getLength());
        return response;
    }

    private void clearClosedSession(Socket clientSocket) {
        // 这里要做的事情, 主要就是遍历上述 sessions hash 表, 把该被关闭的 socket 对应的键值对, 统统删掉.
        List<String> toDeleteChannelId = new ArrayList<>();
        for (Map.Entry<String, Socket> entry : sessions.entrySet()) {
            if (entry.getValue() == clientSocket) {
                // 不能在这里直接删除!!!
                // 这属于使用集合类的一个大忌!!! 一边遍历, 一边删除!!!
                // sessions.remove(entry.getKey());
                toDeleteChannelId.add(entry.getKey());
            }
        }
        for (String channelId : toDeleteChannelId) {
            sessions.remove(channelId);
        }
        System.out.println("[BrokerServer] 清理 session 完成! 被清理的 channelId=" + toDeleteChannelId);
    }

}

启动/停⽌服务器

• 这⾥就是⼀个单纯的 TCP 服务器, 没啥特别的.
• 实现停⽌操作, 主要是为了⽅便后续开展单元测试

    public void start() throws IOException {
        System.out.println("[BrokerServer] 启动!");
        executorService = Executors.newCachedThreadPool();
        try {
            while (runnable) {
                Socket clientSocket = serverSocket.accept();
                // 把处理连接的逻辑丢给这个线程池.
                executorService.submit(() -> {
                    processConnection(clientSocket);
                });
            }
        } catch (SocketException e) {
            System.out.println("[BrokerServer] 服务器停止运行!");
            // e.printStackTrace();
        }
    }

    // 一般来说停止服务器, 就是直接 kill 掉对应进程就行了.
    // 此处还是搞一个单独的停止方法. 主要是用于后续的单元测试.
    public void stop() throws IOException {
        runnable = false;
        // 把线程池中的任务都放弃了. 让线程都销毁.
        executorService.shutdownNow();
        serverSocket.close();
    }

实现处理连接

• 对于 EOFException 和 SocketException , 我们视为客⼾端正常断开连接.
◦ 如果是客⼾端先 close, 后调⽤ DataInputStream 的 read, 则抛出 EOFException
◦ 如果是先调⽤ DataInputStream 的 read, 后客⼾端调⽤ close, 则抛出 SocketException

    // 通过这个方法, 来处理一个客户端的连接.
    // 在这一个连接中, 可能会涉及到多个请求和响应.
    private void processConnection(Socket clientSocket) {
        try (InputStream inputStream = clientSocket.getInputStream();
             OutputStream outputStream = clientSocket.getOutputStream()) {
            // 这里需要按照特定格式来读取并解析. 此时就需要用到 DataInputStream 和 DataOutputStream
            try (DataInputStream dataInputStream = new DataInputStream(inputStream);
                 DataOutputStream dataOutputStream = new DataOutputStream(outputStream)) {
                while (true) {
                    // 1. 读取请求并解析.
                    Request request = readRequest(dataInputStream);
                    // 2. 根据请求计算响应
                    Response response = process(request, clientSocket);
                    // 3. 把响应写回给客户端
                    writeResponse(dataOutputStream, response);
                }
            }
        } catch (EOFException | SocketException e) {
            // 对于这个代码, DataInputStream 如果读到 EOF , 就会抛出一个 EOFException 异常.
            // 需要借助这个异常来结束循环
            System.out.println("[BrokerServer] connection 关闭! 客户端的地址: " + clientSocket.getInetAddress().toString()
                    + ":" + clientSocket.getPort());
        } catch (IOException | ClassNotFoundException | MqException e) {
            System.out.println("[BrokerServer] connection 出现异常!");
            e.printStackTrace();
        } finally {
            try {
                // 当连接处理完了, 就需要记得关闭 socket
                clientSocket.close();
                // 一个 TCP 连接中, 可能包含多个 channel. 需要把当前这个 socket 对应的所有 channel 也顺便清理掉.
                clearClosedSession(clientSocket);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

实现 readRequest

    private Request readRequest(DataInputStream dataInputStream) throws IOException {
        Request request = new Request();
        request.setType(dataInputStream.readInt());
        request.setLength(dataInputStream.readInt());
        byte[] payload = new byte[request.getLength()];
        int n = dataInputStream.read(payload);
        if (n != request.getLength()) {
            throw new IOException("读取请求格式出错!");
        }
        request.setPayload(payload);
        return request;
    }

实现 writeResponse

    private void writeResponse(DataOutputStream dataOutputStream, Response response) throws IOException {
        dataOutputStream.writeInt(response.getType());
        dataOutputStream.writeInt(response.getLength());
        dataOutputStream.write(response.getPayload());
        // 这个刷新缓冲区也是重要的操作!!
        dataOutputStream.flush();
    }

实现处理请求

• 先把请求转换成 BaseArguments , 获取到其中的 channelId 和 rid
• 再根据不同的 type, 分别处理不同的逻辑. (主要是调⽤ virtualHost 中不同的⽅法).
• 针对消息订阅操作, 则需要在存在消息的时候通过回调, 把响应结果写回给对应的客⼾端.
• 最后构造成统⼀的响应

    private Response process(Request request, Socket clientSocket) throws IOException, ClassNotFoundException, MqException {
        // 1. 把 request 中的 payload 做一个初步的解析.
        BasicArguments basicArguments = (BasicArguments) BinaryTool.fromBytes(request.getPayload());
        System.out.println("[Request] rid=" + basicArguments.getRid() + ", channelId=" + basicArguments.getChannelId()
            + ", type=" + request.getType() + ", length=" + request.getLength());
        // 2. 根据 type 的值, 来进一步区分接下来这次请求要干啥.
        boolean ok = true;
        if (request.getType() == 0x1) {
            // 创建 channel
            sessions.put(basicArguments.getChannelId(), clientSocket);
            System.out.println("[BrokerServer] 创建 channel 完成! channelId=" + basicArguments.getChannelId());
        } else if (request.getType() == 0x2) {
            // 销毁 channel
            sessions.remove(basicArguments.getChannelId());
            System.out.println("[BrokerServer] 销毁 channel 完成! channelId=" + basicArguments.getChannelId());
        } else if (request.getType() == 0x3) {
            // 创建交换机. 此时 payload 就是 ExchangeDeclareArguments 对象了.
            ExchangeDeclareArguments arguments = (ExchangeDeclareArguments) basicArguments;
            ok = virtualHost.exchangeDeclare(arguments.getExchangeName(), arguments.getExchangeType(),
                    arguments.isDurable(), arguments.isAutoDelete(), arguments.getArguments());
        } else if (request.getType() == 0x4) {
            ExchangeDeleteArguments arguments = (ExchangeDeleteArguments) basicArguments;
            ok = virtualHost.exchangeDelete(arguments.getExchangeName());
        } else if (request.getType() == 0x5) {
            QueueDeclareArguments arguments = (QueueDeclareArguments) basicArguments;
            ok = virtualHost.queueDeclare(arguments.getQueueName(), arguments.isDurable(),
                    arguments.isExclusive(), arguments.isAutoDelete(), arguments.getArguments());
        } else if (request.getType() == 0x6) {
            QueueDeleteArguments arguments = (QueueDeleteArguments) basicArguments;
            ok = virtualHost.queueDelete((arguments.getQueueName()));
        } else if (request.getType() == 0x7) {
            QueueBindArguments arguments = (QueueBindArguments) basicArguments;
            ok = virtualHost.queueBind(arguments.getQueueName(), arguments.getExchangeName(), arguments.getBindingKey());
        } else if (request.getType() == 0x8) {
            QueueUnbindArguments arguments = (QueueUnbindArguments) basicArguments;
            ok = virtualHost.queueUnbind(arguments.getQueueName(), arguments.getExchangeName());
        } else if (request.getType() == 0x9) {
            BasicPublishArguments arguments = (BasicPublishArguments) basicArguments;
            ok = virtualHost.basicPublish(arguments.getExchangeName(), arguments.getRoutingKey(),
                    arguments.getBasicProperties(), arguments.getBody());
        } else if (request.getType() == 0xa) {
            BasicConsumeArguments arguments = (BasicConsumeArguments) basicArguments;
            ok = virtualHost.basicConsume(arguments.getConsumerTag(), arguments.getQueueName(), arguments.isAutoAck(),
                    new Consumer() {
                        // 这个回调函数要做的工作, 就是把服务器收到的消息可以直接推送回对应的消费者客户端
                        @Override
                        public void handleDelivery(String consumerTag, BasicProperties basicProperties, byte[] body) throws MqException, IOException {
                            // 先知道当前这个收到的消息, 要发给哪个客户端.
                            // 此处 consumerTag 其实是 channelId. 根据 channelId 去 sessions 中查询, 就可以得到对应的
                            // socket 对象了, 从而可以往里面发送数据了
                            // 1. 根据 channelId 找到 socket 对象
                            Socket clientSocket = sessions.get(consumerTag);
                            if (clientSocket == null || clientSocket.isClosed()) {
                                throw new MqException("[BrokerServer] 订阅消息的客户端已经关闭!");
                            }
                            // 2. 构造响应数据
                            SubScribeReturns subScribeReturns = new SubScribeReturns();
                            subScribeReturns.setChannelId(consumerTag);
                            subScribeReturns.setRid(""); // 由于这里只有响应, 没有请求, 不需要去对应. rid 暂时不需要.
                            subScribeReturns.setOk(true);
                            subScribeReturns.setConsumerTag(consumerTag);
                            subScribeReturns.setBasicProperties(basicProperties);
                            subScribeReturns.setBody(body);
                            byte[] payload = BinaryTool.toBytes(subScribeReturns);
                            Response response = new Response();
                            // 0xc 表示服务器给消费者客户端推送的消息数据.
                            response.setType(0xc);
                            // response 的 payload 就是一个 SubScribeReturns
                            response.setLength(payload.length);
                            response.setPayload(payload);
                            // 3. 把数据写回给客户端.
                            //    注意! 此处的 dataOutputStream 这个对象不能 close !!!
                            //    如果 把 dataOutputStream 关闭, 就会直接把 clientSocket 里的 outputStream 也关了.
                            //    此时就无法继续往 socket 中写入后续数据了.
                            DataOutputStream dataOutputStream = new DataOutputStream(clientSocket.getOutputStream());
                            writeResponse(dataOutputStream, response);
                        }
                    });
        } else if (request.getType() == 0xb) {
            // 调用 basicAck 确认消息.
            BasicAckArguments arguments = (BasicAckArguments) basicArguments;
            ok = virtualHost.basicAck(arguments.getQueueName(), arguments.getMessageId());
        } else {
            // 当前的 type 是非法的.
            throw new MqException("[BrokerServer] 未知的 type! type=" + request.getType());
        }
        // 3. 构造响应
        BasicReturns basicReturns = new BasicReturns();
        basicReturns.setChannelId(basicArguments.getChannelId());
        basicReturns.setRid(basicArguments.getRid());
        basicReturns.setOk(ok);
        byte[] payload = BinaryTool.toBytes(basicReturns);
        Response response = new Response();
        response.setType(request.getType());
        response.setLength(payload.length);
        response.setPayload(payload);
        System.out.println("[Response] rid=" + basicReturns.getRid() + ", channelId=" + basicReturns.getChannelId()
            + ", type=" + response.getType() + ", length=" + response.getLength());
        return response;
    }

实现 clearClosedSession

• 如果客⼾端只关闭了 Connection, 没关闭 Connection 中包含的 Channel, 也没关系, 在这⾥统⼀进⾏清理.
• 注意迭代器失效问题.

    private void clearClosedSession(Socket clientSocket) {
        // 这里要做的事情, 主要就是遍历上述 sessions hash 表, 把该被关闭的 socket 对应的键值对, 统统删掉.
        List<String> toDeleteChannelId = new ArrayList<>();
        for (Map.Entry<String, Socket> entry : sessions.entrySet()) {
            if (entry.getValue() == clientSocket) {
                // 不能在这里直接删除!!!
                // 这属于使用集合类的一个大忌!!! 一边遍历, 一边删除!!!
                // sessions.remove(entry.getKey());
                toDeleteChannelId.add(entry.getKey());
            }
        }
        for (String channelId : toDeleteChannelId) {
            sessions.remove(channelId);
        }
        System.out.println("[BrokerServer] 清理 session 完成! 被清理的 channelId=" + toDeleteChannelId);
    }

⼗三. 实现客⼾端

创建 ConnectionFactory

⽤来创建连接的⼯⼚类.
• 当前没有实现⽤⼾认证和多虚拟主机, ⽤⼾名密码可以暂时先不要

package com.example.mq.mqclient;

import java.io.IOException;

public class ConnectionFactory {
    // broker server 的 ip 地址
    private String host;
    // broker server 的端口号
    private int port;

    // 访问 broker server 的哪个虚拟主机.
    // 下列几个属性暂时先都不搞了.
//    private String virtualHostName;
//    private String username;
//    private String password;

    public Connection newConnection() throws IOException {
        Connection connection = new Connection(host, port);
        return connection;
    }

    public String getHost() {
        return host;
    }

    public void setHost(String host) {
        this.host = host;
    }

    public int getPort() {
        return port;
    }

    public void setPort(int port) {
        this.port = port;
    }
}

Connection 和 Channel 的定义

⼀个客⼾端可以创建多个 Connection.
⼀个 Connection 对应⼀个 socket, ⼀个 TCP 连接.
⼀个 Connection 可以包含多个 Channel

1) Connection 的定义

• Socket 是客⼾端持有的套接字. InputStream OutputStream DataInputStream DataOutputStream 均为 socket 通信的接⼝.
• channelMap ⽤来管理该连接中所有的 Channel.
• callbackPool 是⽤来在客⼾端这边执⾏⽤⼾回调的线程池.

public class Connection {
    private Socket socket = null;
    // 需要管理多个 channel. 使用一个 hash 表把若干个 channel 组织起来.
    private ConcurrentHashMap<String, Channel> channelMap = new ConcurrentHashMap<>();

    private InputStream inputStream;
    private OutputStream outputStream;
    private DataInputStream dataInputStream;
    private DataOutputStream dataOutputStream;

    private ExecutorService callbackPool = null;

    public Connection(String host, int port) throws IOException {
        socket = new Socket(host, port);
        inputStream = socket.getInputStream();
        outputStream = socket.getOutputStream();
        dataInputStream = new DataInputStream(inputStream);
        dataOutputStream = new DataOutputStream(outputStream);

        callbackPool = Executors.newFixedThreadPool(4);

        // 创建一个扫描线程, 由这个线程负责不停的从 socket 中读取响应数据. 把这个响应数据再交给对应的 channel 负责处理.
        Thread t = new Thread(() -> {
            try {
                while (!socket.isClosed()) {
                    Response response = readResponse();
                    dispatchResponse(response);
                }
            } catch (SocketException e) {
                // 连接正常断开的. 此时这个异常直接忽略.
                System.out.println("[Connection] 连接正常断开!");
            } catch (IOException | ClassNotFoundException | MqException e) {
                System.out.println("[Connection] 连接异常断开!");
                e.printStackTrace();
            }
        });
        t.start();
    }

    public void close() {
        // 关闭 Connection 释放上述资源
        try {
            callbackPool.shutdownNow();
            channelMap.clear();
            inputStream.close();
            outputStream.close();
            socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // 使用这个方法来分别处理, 当前的响应是一个针对控制请求的响应, 还是服务器推送的消息.
    private void dispatchResponse(Response response) throws IOException, ClassNotFoundException, MqException {
        if (response.getType() == 0xc) {
            // 服务器推送来的消息数据
            SubScribeReturns subScribeReturns = (SubScribeReturns) BinaryTool.fromBytes(response.getPayload());
            // 根据 channelId 找到对应的 channel 对象
            Channel channel = channelMap.get(subScribeReturns.getChannelId());
            if (channel == null) {
                throw new MqException("[Connection] 该消息对应的 channel 在客户端中不存在! channelId=" + channel.getChannelId());
            }
            // 执行该 channel 对象内部的回调.
            callbackPool.submit(() -> {
                try {
                    channel.getConsumer().handleDelivery(subScribeReturns.getConsumerTag(), subScribeReturns.getBasicProperties(),
                            subScribeReturns.getBody());
                } catch (MqException | IOException e) {
                    e.printStackTrace();
                }
            });
        } else {
            // 当前响应是针对刚才的控制请求的响应
            BasicReturns basicReturns = (BasicReturns) BinaryTool.fromBytes(response.getPayload());
            // 把这个结果放到对应的 channel 的 hash 表中.
            Channel channel = channelMap.get(basicReturns.getChannelId());
            if (channel == null) {
                throw new MqException("[Connection] 该消息对应的 channel 在客户端中不存在! channelId=" + channel.getChannelId());
            }
            channel.putReturns(basicReturns);
        }
    }

    // 发送请求
    public void writeRequest(Request request) throws IOException {
        dataOutputStream.writeInt(request.getType());
        dataOutputStream.writeInt(request.getLength());
        dataOutputStream.write(request.getPayload());
        dataOutputStream.flush();
        System.out.println("[Connection] 发送请求! type=" + request.getType() + ", length=" + request.getLength());
    }

    // 读取响应
    public Response readResponse() throws IOException {
        Response response = new Response();
        response.setType(dataInputStream.readInt());
        response.setLength(dataInputStream.readInt());
        byte[] payload = new byte[response.getLength()];
        int n = dataInputStream.read(payload);
        if (n != response.getLength()) {
            throw new IOException("读取的响应数据不完整!");
        }
        response.setPayload(payload);
        System.out.println("[Connection] 收到响应! type=" + response.getType() + ", length=" + response.getLength());
        return response;
    }

    // 通过这个方法, 在 Connection 中能够创建出一个 Channel
    public Channel createChannel() throws IOException {
        String channelId = "C-" + UUID.randomUUID().toString();
        Channel channel = new Channel(channelId, this);
        // 把这个 channel 对象放到 Connection 管理 channel 的 哈希表 中.
        channelMap.put(channelId, channel);
        // 同时也需要把 "创建 channel" 的这个消息也告诉服务器.
        boolean ok = channel.createChannel();
        if (!ok) {
            // 服务器这里创建失败了!! 整个这次创建 channel 操作不顺利!!
            // 把刚才已经加入 hash 表的键值对, 再删了.
            channelMap.remove(channelId);
            return null;
        }
        return channel;
    }
}

2) Channel 的定义

• channelId 为 channel 的⾝份标识, 使⽤ UUID 标识.
• Connection 为 channel 对应的连接.
• baseReturnsMap ⽤来保存响应的返回值. 放到这个哈希表中⽅便和请求匹配.
• consumer 为消费者的回调(⽤⼾注册的). 对于消息响应, 应该调⽤这个回调处理消息.

package com.example.mq.mqclient;

import com.example.mq.common.*;
import com.example.mq.mqserver.core.BasicProperties;
import com.example.mq.mqserver.core.ExchangeType;

import java.io.IOException;
import java.lang.ref.ReferenceQueue;
import java.util.Map;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;

public class Channel {
    private String channelId;
    // 当前这个 channel 属于哪个连接.
    private Connection connection;
    // 用来存储后续客户端收到的服务器的响应.
    private ConcurrentHashMap<String, BasicReturns> basicReturnsMap = new ConcurrentHashMap<>();
    // 如果当前 Channel 订阅了某个队列, 就需要在此处记录下对应回调是啥. 当该队列的消息返回回来的时候, 调用回调.
    // 此处约定一个 Channel 中只能有一个回调.
    private Consumer consumer = null;

    public Channel(String channelId, Connection connection) {
        this.channelId = channelId;
        this.connection = connection;
    }

    // 在这个方法中, 和服务器进行交互, 告知服务器, 此处客户端创建了新的 channel 了.
    public boolean createChannel() throws IOException {
        // 对于创建 Channel 操作来说, payload 就是一个 basicArguments 对象
        BasicArguments basicArguments = new BasicArguments();
        basicArguments.setChannelId(channelId);
        basicArguments.setRid(generateRid());
        byte[] payload = BinaryTool.toBytes(basicArguments);

        Request request = new Request();
        request.setType(0x1);
        request.setLength(payload.length);
        request.setPayload(payload);

        // 构造出完整请求之后, 就可以发送这个请求了.
        connection.writeRequest(request);
        // 等待服务器的响应
        BasicReturns basicReturns = waitResult(basicArguments.getRid());
        return basicReturns.isOk();
    }

    // 期望使用这个方法来阻塞等待服务器的响应.
    private BasicReturns waitResult(String rid) {
        BasicReturns basicReturns = null;
        while ((basicReturns = basicReturnsMap.get(rid)) == null) {
            // 如果查询结果为 null, 说明包裹还没回来.
            // 此时就需要阻塞等待.
            synchronized (this) {
                try {
                    wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
        // 读取成功之后, 还需要把这个消息从哈希表中删除掉.
        basicReturnsMap.remove(rid);
        return basicReturns;
    }

    public void putReturns(BasicReturns basicReturns) {
        basicReturnsMap.put(basicReturns.getRid(), basicReturns);
        synchronized (this) {
            // 当前也不知道有多少个线程在等待上述的这个响应.
            // 把所有的等待的线程都唤醒.
            notifyAll();
        }
    }

    private String generateRid() {
        return "R-" + UUID.randomUUID().toString();
    }

    // 关闭 channel, 给服务器发送一个 type = 0x2 的请求
    public boolean close() throws IOException {
        BasicArguments basicArguments = new BasicArguments();
        basicArguments.setRid(generateRid());
        basicArguments.setChannelId(channelId);
        byte[] payload = BinaryTool.toBytes(basicArguments);

        Request request = new Request();
        request.setType(0x2);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(basicArguments.getRid());
        return basicReturns.isOk();
    }

    // 创建交换机
    public boolean exchangeDeclare(String exchangeName, ExchangeType exchangeType, boolean durable, boolean autoDelete,
                                   Map<String, Object> arguments) throws IOException {
        ExchangeDeclareArguments exchangeDeclareArguments = new ExchangeDeclareArguments();
        exchangeDeclareArguments.setRid(generateRid());
        exchangeDeclareArguments.setChannelId(channelId);
        exchangeDeclareArguments.setExchangeName(exchangeName);
        exchangeDeclareArguments.setExchangeType(exchangeType);
        exchangeDeclareArguments.setDurable(durable);
        exchangeDeclareArguments.setAutoDelete(autoDelete);
        exchangeDeclareArguments.setArguments(arguments);
        byte[] payload = BinaryTool.toBytes(exchangeDeclareArguments);

        Request request = new Request();
        request.setType(0x3);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(exchangeDeclareArguments.getRid());
        return basicReturns.isOk();
    }

    // 删除交换机
    public boolean exchangeDelete(String exchangeName) throws IOException {
        ExchangeDeleteArguments arguments = new ExchangeDeleteArguments();
        arguments.setRid(generateRid());
        arguments.setChannelId(channelId);
        arguments.setExchangeName(exchangeName);
        byte[] payload = BinaryTool.toBytes(arguments);

        Request request = new Request();
        request.setType(0x4);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(arguments.getRid());
        return basicReturns.isOk();
    }

    // 创建队列
    public boolean queueDeclare(String queueName, boolean durable, boolean exclusive, boolean autoDelete,
                                Map<String, Object> arguments) throws IOException {
        QueueDeclareArguments queueDeclareArguments = new QueueDeclareArguments();
        queueDeclareArguments.setRid(generateRid());
        queueDeclareArguments.setChannelId(channelId);
        queueDeclareArguments.setQueueName(queueName);
        queueDeclareArguments.setDurable(durable);
        queueDeclareArguments.setExclusive(exclusive);
        queueDeclareArguments.setAutoDelete(autoDelete);
        queueDeclareArguments.setArguments(arguments);
        byte[] payload = BinaryTool.toBytes(queueDeclareArguments);

        Request request = new Request();
        request.setType(0x5);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(queueDeclareArguments.getRid());
        return basicReturns.isOk();
    }

    // 删除队列
    public boolean queueDelete(String queueName) throws IOException {
        QueueDeleteArguments arguments = new QueueDeleteArguments();
        arguments.setRid(generateRid());
        arguments.setChannelId(channelId);
        arguments.setQueueName(queueName);
        byte[] payload = BinaryTool.toBytes(arguments);

        Request request = new Request();
        request.setType(0x6);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(arguments.getRid());
        return basicReturns.isOk();
    }

    // 创建绑定
    public boolean queueBind(String queueName, String exchangeName, String bindingKey) throws IOException {
        QueueBindArguments arguments = new QueueBindArguments();
        arguments.setRid(generateRid());
        arguments.setChannelId(channelId);
        arguments.setQueueName(queueName);
        arguments.setExchangeName(exchangeName);
        arguments.setBindingKey(bindingKey);
        byte[] payload = BinaryTool.toBytes(arguments);

        Request request = new Request();
        request.setType(0x7);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(arguments.getRid());
        return basicReturns.isOk();
    }

    // 解除绑定
    public boolean queueUnbind(String queueName, String exchangeName) throws IOException {
        QueueUnbindArguments arguments = new QueueUnbindArguments();
        arguments.setRid(generateRid());
        arguments.setChannelId(channelId);
        arguments.setQueueName(queueName);
        arguments.setExchangeName(exchangeName);
        byte[] payload = BinaryTool.toBytes(arguments);

        Request request = new Request();
        request.setType(0x8);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(arguments.getRid());
        return basicReturns.isOk();
    }

    // 发送消息
    public boolean basicPublish(String exchangeName, String routingKey, BasicProperties basicProperties, byte[] body) throws IOException {
        BasicPublishArguments arguments = new BasicPublishArguments();
        arguments.setRid(generateRid());
        arguments.setChannelId(channelId);
        arguments.setExchangeName(exchangeName);
        arguments.setRoutingKey(routingKey);
        arguments.setBasicProperties(basicProperties);
        arguments.setBody(body);
        byte[] payload = BinaryTool.toBytes(arguments);

        Request request = new Request();
        request.setType(0x9);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(arguments.getRid());
        return basicReturns.isOk();
    }

    // 订阅消息
    public boolean basicConsume(String queueName, boolean autoAck, Consumer consumer) throws MqException, IOException {
        // 先设置回调.
        if (this.consumer != null) {
            throw new MqException("该 channel 已经设置过消费消息的回调了, 不能重复设置!");
        }
        this.consumer = consumer;

        BasicConsumeArguments arguments = new BasicConsumeArguments();
        arguments.setRid(generateRid());
        arguments.setChannelId(channelId);
        arguments.setConsumerTag(channelId);  // 此处 consumerTag 也使用 channelId 来表示了.
        arguments.setQueueName(queueName);
        arguments.setAutoAck(autoAck);
        byte[] payload = BinaryTool.toBytes(arguments);

        Request request = new Request();
        request.setType(0xa);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(arguments.getRid());
        return basicReturns.isOk();
    }

    // 确认消息
    public boolean basicAck(String queueName, String messageId) throws IOException {
        BasicAckArguments arguments = new BasicAckArguments();
        arguments.setRid(generateRid());
        arguments.setChannelId(channelId);
        arguments.setQueueName(queueName);
        arguments.setMessageId(messageId);
        byte[] payload = BinaryTool.toBytes(arguments);

        Request request = new Request();
        request.setType(0xb);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(arguments.getRid());
        return basicReturns.isOk();
    }

    public String getChannelId() {
        return channelId;
    }

    public void setChannelId(String channelId) {
        this.channelId = channelId;
    }

    public Connection getConnection() {
        return connection;
    }

    public void setConnection(Connection connection) {
        this.connection = connection;
    }

    public ConcurrentHashMap<String, BasicReturns> getBasicReturnsMap() {
        return basicReturnsMap;
    }

    public void setBasicReturnsMap(ConcurrentHashMap<String, BasicReturns> basicReturnsMap) {
        this.basicReturnsMap = basicReturnsMap;
    }

    public Consumer getConsumer() {
        return consumer;
    }

    public void setConsumer(Consumer consumer) {
        this.consumer = consumer;
    }

}

Connection

封装请求响应读写操作

在 Connection 中, 实现下列⽅法

    // 发送请求
    public void writeRequest(Request request) throws IOException {
        dataOutputStream.writeInt(request.getType());
        dataOutputStream.writeInt(request.getLength());
        dataOutputStream.write(request.getPayload());
        dataOutputStream.flush();
        System.out.println("[Connection] 发送请求! type=" + request.getType() + ", length=" + request.getLength());
    }

    // 读取响应
    public Response readResponse() throws IOException {
        Response response = new Response();
        response.setType(dataInputStream.readInt());
        response.setLength(dataInputStream.readInt());
        byte[] payload = new byte[response.getLength()];
        int n = dataInputStream.read(payload);
        if (n != response.getLength()) {
            throw new IOException("读取的响应数据不完整!");
        }
        response.setPayload(payload);
        System.out.println("[Connection] 收到响应! type=" + response.getType() + ", length=" + response.getLength());
        return response;
    }

创建 channel

在 Connection 中, 定义下列⽅法来创建⼀个 channel

    // 通过这个方法, 在 Connection 中能够创建出一个 Channel
    public Channel createChannel() throws IOException {
        String channelId = "C-" + UUID.randomUUID().toString();
        Channel channel = new Channel(channelId, this);
        // 把这个 channel 对象放到 Connection 管理 channel 的 哈希表 中.
        channelMap.put(channelId, channel);
        // 同时也需要把 "创建 channel" 的这个消息也告诉服务器.
        boolean ok = channel.createChannel();
        if (!ok) {
            // 服务器这里创建失败了!! 整个这次创建 channel 操作不顺利!!
            // 把刚才已经加入 hash 表的键值对, 再删了.
            channelMap.remove(channelId);
            return null;
        }
        return channel;
    }

Channel

发送请求

通过 Channel 提供请求的发送操作.

1) 创建 channel

    // 在这个方法中, 和服务器进行交互, 告知服务器, 此处客户端创建了新的 channel 了.
    public boolean createChannel() throws IOException {
        // 对于创建 Channel 操作来说, payload 就是一个 basicArguments 对象
        BasicArguments basicArguments = new BasicArguments();
        basicArguments.setChannelId(channelId);
        basicArguments.setRid(generateRid());
        byte[] payload = BinaryTool.toBytes(basicArguments);

        Request request = new Request();
        request.setType(0x1);
        request.setLength(payload.length);
        request.setPayload(payload);

        // 构造出完整请求之后, 就可以发送这个请求了.
        connection.writeRequest(request);
        // 等待服务器的响应
        BasicReturns basicReturns = waitResult(basicArguments.getRid());
        return basicReturns.isOk();
    }

generateRid 的实现

    private String generateRid() {
        return "R-" + UUID.randomUUID().toString();
    }

waitResult 的实现
• 由于服务器的响应是异步的. 此处通过 waitResult 实现同步等待的效果

    // 期望使用这个方法来阻塞等待服务器的响应.
    private BasicReturns waitResult(String rid) {
        BasicReturns basicReturns = null;
        while ((basicReturns = basicReturnsMap.get(rid)) == null) {
            // 如果查询结果为 null, 说明包裹还没回来.
            // 此时就需要阻塞等待.
            synchronized (this) {
                try {
                    wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
        // 读取成功之后, 还需要把这个消息从哈希表中删除掉.
        basicReturnsMap.remove(rid);
        return basicReturns;
    }

2) 关闭 channel

    // 关闭 channel, 给服务器发送一个 type = 0x2 的请求
    public boolean close() throws IOException {
        BasicArguments basicArguments = new BasicArguments();
        basicArguments.setRid(generateRid());
        basicArguments.setChannelId(channelId);
        byte[] payload = BinaryTool.toBytes(basicArguments);

        Request request = new Request();
        request.setType(0x2);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(basicArguments.getRid());
        return basicReturns.isOk();
    }

3) 创建交换机

    // 创建交换机
    public boolean exchangeDeclare(String exchangeName, ExchangeType exchangeType, boolean durable, boolean autoDelete,
                                   Map<String, Object> arguments) throws IOException {
        ExchangeDeclareArguments exchangeDeclareArguments = new ExchangeDeclareArguments();
        exchangeDeclareArguments.setRid(generateRid());
        exchangeDeclareArguments.setChannelId(channelId);
        exchangeDeclareArguments.setExchangeName(exchangeName);
        exchangeDeclareArguments.setExchangeType(exchangeType);
        exchangeDeclareArguments.setDurable(durable);
        exchangeDeclareArguments.setAutoDelete(autoDelete);
        exchangeDeclareArguments.setArguments(arguments);
        byte[] payload = BinaryTool.toBytes(exchangeDeclareArguments);

        Request request = new Request();
        request.setType(0x3);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(exchangeDeclareArguments.getRid());
        return basicReturns.isOk();
    }

4) 删除交换机

    // 删除交换机
    public boolean exchangeDelete(String exchangeName) throws IOException {
        ExchangeDeleteArguments arguments = new ExchangeDeleteArguments();
        arguments.setRid(generateRid());
        arguments.setChannelId(channelId);
        arguments.setExchangeName(exchangeName);
        byte[] payload = BinaryTool.toBytes(arguments);

        Request request = new Request();
        request.setType(0x4);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(arguments.getRid());
        return basicReturns.isOk();
    }

5) 创建队列

   // 创建队列
    public boolean queueDeclare(String queueName, boolean durable, boolean exclusive, boolean autoDelete,
                                Map<String, Object> arguments) throws IOException {
        QueueDeclareArguments queueDeclareArguments = new QueueDeclareArguments();
        queueDeclareArguments.setRid(generateRid());
        queueDeclareArguments.setChannelId(channelId);
        queueDeclareArguments.setQueueName(queueName);
        queueDeclareArguments.setDurable(durable);
        queueDeclareArguments.setExclusive(exclusive);
        queueDeclareArguments.setAutoDelete(autoDelete);
        queueDeclareArguments.setArguments(arguments);
        byte[] payload = BinaryTool.toBytes(queueDeclareArguments);

        Request request = new Request();
        request.setType(0x5);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(queueDeclareArguments.getRid());
        return basicReturns.isOk();
    }

6) 删除队列

    // 删除队列
    public boolean queueDelete(String queueName) throws IOException {
        QueueDeleteArguments arguments = new QueueDeleteArguments();
        arguments.setRid(generateRid());
        arguments.setChannelId(channelId);
        arguments.setQueueName(queueName);
        byte[] payload = BinaryTool.toBytes(arguments);

        Request request = new Request();
        request.setType(0x6);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(arguments.getRid());
        return basicReturns.isOk();
    }

7) 创建绑定

    // 创建绑定
    public boolean queueBind(String queueName, String exchangeName, String bindingKey) throws IOException {
        QueueBindArguments arguments = new QueueBindArguments();
        arguments.setRid(generateRid());
        arguments.setChannelId(channelId);
        arguments.setQueueName(queueName);
        arguments.setExchangeName(exchangeName);
        arguments.setBindingKey(bindingKey);
        byte[] payload = BinaryTool.toBytes(arguments);

        Request request = new Request();
        request.setType(0x7);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(arguments.getRid());
        return basicReturns.isOk();
    }

8) 删除绑定

    // 解除绑定
    public boolean queueUnbind(String queueName, String exchangeName) throws IOException {
        QueueUnbindArguments arguments = new QueueUnbindArguments();
        arguments.setRid(generateRid());
        arguments.setChannelId(channelId);
        arguments.setQueueName(queueName);
        arguments.setExchangeName(exchangeName);
        byte[] payload = BinaryTool.toBytes(arguments);

        Request request = new Request();
        request.setType(0x8);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(arguments.getRid());
        return basicReturns.isOk();
    }

9) 发送消息

    // 发送消息
    public boolean basicPublish(String exchangeName, String routingKey, BasicProperties basicProperties, byte[] body) throws IOException {
        BasicPublishArguments arguments = new BasicPublishArguments();
        arguments.setRid(generateRid());
        arguments.setChannelId(channelId);
        arguments.setExchangeName(exchangeName);
        arguments.setRoutingKey(routingKey);
        arguments.setBasicProperties(basicProperties);
        arguments.setBody(body);
        byte[] payload = BinaryTool.toBytes(arguments);

        Request request = new Request();
        request.setType(0x9);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(arguments.getRid());
        return basicReturns.isOk();
    }

10) 订阅消息

    // 订阅消息
    public boolean basicConsume(String queueName, boolean autoAck, Consumer consumer) throws MqException, IOException {
        // 先设置回调.
        if (this.consumer != null) {
            throw new MqException("该 channel 已经设置过消费消息的回调了, 不能重复设置!");
        }
        this.consumer = consumer;

        BasicConsumeArguments arguments = new BasicConsumeArguments();
        arguments.setRid(generateRid());
        arguments.setChannelId(channelId);
        arguments.setConsumerTag(channelId);  // 此处 consumerTag 也使用 channelId 来表示了.
        arguments.setQueueName(queueName);
        arguments.setAutoAck(autoAck);
        byte[] payload = BinaryTool.toBytes(arguments);

        Request request = new Request();
        request.setType(0xa);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(arguments.getRid());
        return basicReturns.isOk();
    }

11) 确认消息

    // 确认消息
    public boolean basicAck(String queueName, String messageId) throws IOException {
        BasicAckArguments arguments = new BasicAckArguments();
        arguments.setRid(generateRid());
        arguments.setChannelId(channelId);
        arguments.setQueueName(queueName);
        arguments.setMessageId(messageId);
        byte[] payload = BinaryTool.toBytes(arguments);

        Request request = new Request();
        request.setType(0xb);
        request.setLength(payload.length);
        request.setPayload(payload);

        connection.writeRequest(request);
        BasicReturns basicReturns = waitResult(arguments.getRid());
        return basicReturns.isOk();
    }

⼩结

上述发送请求的操作, 逻辑基本⼀致. 构造参数 + 构造请求 + 发送 + 等待结果

处理响应

1) 创建扫描线程

创建⼀个扫描线程, ⽤来不停的读取 socket 中的响应数据.
注意: ⼀个 Connection 中可能包含多个 channel, 需要把响应分别放到对应的 channel 中.

    public Connection(String host, int port) throws IOException {
        socket = new Socket(host, port);
        inputStream = socket.getInputStream();
        outputStream = socket.getOutputStream();
        dataInputStream = new DataInputStream(inputStream);
        dataOutputStream = new DataOutputStream(outputStream);

        callbackPool = Executors.newFixedThreadPool(4);

        // 创建一个扫描线程, 由这个线程负责不停的从 socket 中读取响应数据. 把这个响应数据再交给对应的 channel 负责处理.
        Thread t = new Thread(() -> {
            try {
                while (!socket.isClosed()) {
                    Response response = readResponse();
                    dispatchResponse(response);
                }
            } catch (SocketException e) {
                // 连接正常断开的. 此时这个异常直接忽略.
                System.out.println("[Connection] 连接正常断开!");
            } catch (IOException | ClassNotFoundException | MqException e) {
                System.out.println("[Connection] 连接异常断开!");
                e.printStackTrace();
            }
        });
        t.start();
    }

2) 实现响应的分发

给 Connection 创建 dispatchResponse ⽅法.
• 针对服务器返回的控制响应和消息响应, 分别处理.
◦ 如果是订阅数据, 则调⽤ channel 中的回调.
◦ 如果是控制消息, 直接放到结果集合中.

    // 使用这个方法来分别处理, 当前的响应是一个针对控制请求的响应, 还是服务器推送的消息.
    private void dispatchResponse(Response response) throws IOException, ClassNotFoundException, MqException {
        if (response.getType() == 0xc) {
            // 服务器推送来的消息数据
            SubScribeReturns subScribeReturns = (SubScribeReturns) BinaryTool.fromBytes(response.getPayload());
            // 根据 channelId 找到对应的 channel 对象
            Channel channel = channelMap.get(subScribeReturns.getChannelId());
            if (channel == null) {
                throw new MqException("[Connection] 该消息对应的 channel 在客户端中不存在! channelId=" + channel.getChannelId());
            }
            // 执行该 channel 对象内部的回调.
            callbackPool.submit(() -> {
                try {
                    channel.getConsumer().handleDelivery(subScribeReturns.getConsumerTag(), subScribeReturns.getBasicProperties(),
                            subScribeReturns.getBody());
                } catch (MqException | IOException e) {
                    e.printStackTrace();
                }
            });
        } else {
            // 当前响应是针对刚才的控制请求的响应
            BasicReturns basicReturns = (BasicReturns) BinaryTool.fromBytes(response.getPayload());
            // 把这个结果放到对应的 channel 的 hash 表中.
            Channel channel = channelMap.get(basicReturns.getChannelId());
            if (channel == null) {
                throw new MqException("[Connection] 该消息对应的 channel 在客户端中不存在! channelId=" + channel.getChannelId());
            }
            channel.putReturns(basicReturns);
        }
    }

3) 实现 channel.putReturns

把响应放到响应的 hash 表中, 同时唤醒等待响应的线程去消费.

    public void putReturns(BasicReturns basicReturns) {
        basicReturnsMap.put(basicReturns.getRid(), basicReturns);
        synchronized (this) {
            // 当前也不知道有多少个线程在等待上述的这个响应.
            // 把所有的等待的线程都唤醒.
            notifyAll();
        }
    }

关闭 Connection

给 Connection 实现 close ⽅法

    public void close() {
        // 关闭 Connection 释放上述资源
        try {
            callbackPool.shutdownNow();
            channelMap.clear();
            inputStream.close();
            outputStream.close();
            socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

测试客⼾端-服务器

public class MqClientTests {
    private BrokerServer brokerServer = null;
    private ConnectionFactory factory = null;
    private Thread t = null;

    @BeforeEach
    public void setUp() throws IOException {
        // 1. 先启动服务器
        MqApplication.context = SpringApplication.run(MqApplication.class);
        brokerServer = new BrokerServer(9090);
        t = new Thread(() -> {
            // 这个 start 方法会进入一个死循环. 使用一个新的线程来运行 start 即可!
            try {
                brokerServer.start();
            } catch (IOException e) {
                e.printStackTrace();
            }
        });
        t.start();

        // 2. 配置 ConnectionFactory
        factory = new ConnectionFactory();
        factory.setHost("127.0.0.1");
        factory.setPort(9090);
    }

    @AfterEach
    public void tearDown() throws IOException {
        // 停止服务器
        brokerServer.stop();
        // t.join();
        MqApplication.context.close();

        // 删除必要的文件
        File file = new File("./data");
        FileUtils.deleteDirectory(file);

        factory = null;
    }

    @Test
    public void testConnection() throws IOException {
        Connection connection = factory.newConnection();
        Assertions.assertNotNull(connection);
    }

    @Test
    public void testChannel() throws IOException {
        Connection connection = factory.newConnection();
        Assertions.assertNotNull(connection);
        Channel channel = connection.createChannel();
        Assertions.assertNotNull(channel);
    }

    @Test
    public void testExchange() throws IOException {
        Connection connection = factory.newConnection();
        Assertions.assertNotNull(connection);
        Channel channel = connection.createChannel();
        Assertions.assertNotNull(channel);

        boolean ok = channel.exchangeDeclare("testExchange", ExchangeType.DIRECT, true, false, null);
        Assertions.assertTrue(ok);

        ok = channel.exchangeDelete("testExchange");
        Assertions.assertTrue(ok);

        // 此处稳妥起见, 把改关闭的要进行关闭.
        channel.close();
        connection.close();
    }

    @Test
    public void testQueue() throws IOException {
        Connection connection = factory.newConnection();
        Assertions.assertNotNull(connection);
        Channel channel = connection.createChannel();
        Assertions.assertNotNull(channel);

        boolean ok = channel.queueDeclare("testQueue", true, false, false, null);
        Assertions.assertTrue(ok);

        ok = channel.queueDelete("testQueue");
        Assertions.assertTrue(ok);

        channel.close();
        connection.close();
    }

    @Test
    public void testBinding() throws IOException {
        Connection connection = factory.newConnection();
        Assertions.assertNotNull(connection);
        Channel channel = connection.createChannel();
        Assertions.assertNotNull(channel);

        boolean ok = channel.exchangeDeclare("testExchange", ExchangeType.DIRECT, true, false, null);
        Assertions.assertTrue(ok);
        ok = channel.queueDeclare("testQueue", true, false, false, null);
        Assertions.assertTrue(ok);

        ok = channel.queueBind("testQueue", "testExchange", "testBindingKey");
        Assertions.assertTrue(ok);

        ok = channel.queueUnbind("testQueue", "testExchange");
        Assertions.assertTrue(ok);

        channel.close();
        connection.close();
    }

    @Test
    public void testMessage() throws IOException, MqException, InterruptedException {
        Connection connection = factory.newConnection();
        Assertions.assertNotNull(connection);
        Channel channel = connection.createChannel();
        Assertions.assertNotNull(channel);

        boolean ok = channel.exchangeDeclare("testExchange", ExchangeType.DIRECT, true, false, null);
        Assertions.assertTrue(ok);
        ok = channel.queueDeclare("testQueue", true, false, false, null);
        Assertions.assertTrue(ok);

        byte[] requestBody = "hello".getBytes();
        ok = channel.basicPublish("testExchange", "testQueue", null, requestBody);
        Assertions.assertTrue(ok);

        ok = channel.basicConsume("testQueue", true, new Consumer() {
            @Override
            public void handleDelivery(String consumerTag, BasicProperties basicProperties, byte[] body) throws MqException, IOException {
                System.out.println("[消费数据] 开始!");
                System.out.println("consumerTag=" + consumerTag);
                System.out.println("basicProperties=" + basicProperties);
                Assertions.assertArrayEquals(requestBody, body);
                System.out.println("[消费数据] 结束!");
            }
        });
        Assertions.assertTrue(ok);

        Thread.sleep(500);

        channel.close();
        connection.close();
    }
}

⼗四. 案例: 基于 MQ 的⽣产者消费者模型

/*
 * 这个类表示一个消费者.
 * 通常这个类也应该是在一个独立的服务器中被执行
 */
public class DemoConsumer {
    public static void main(String[] args) throws IOException, MqException, InterruptedException {
        System.out.println("启动消费者!");
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("127.0.0.1");
        factory.setPort(9090);

        Connection connection = factory.newConnection();
        Channel channel = connection.createChannel();

        channel.exchangeDeclare("testExchange", ExchangeType.DIRECT, true, false, null);
        channel.queueDeclare("testQueue", true, false, false, null);

        channel.basicConsume("testQueue", true, new Consumer() {
            @Override
            public void handleDelivery(String consumerTag, BasicProperties basicProperties, byte[] body) throws MqException, IOException {
                System.out.println("[消费数据] 开始!");
                System.out.println("consumerTag=" + consumerTag);
                System.out.println("basicProperties=" + basicProperties);
                String bodyString = new String(body, 0, body.length);
                System.out.println("body=" + bodyString);
                System.out.println("[消费数据] 结束!");
            }
        });

        // 由于消费者也不知道生产者要生产多少, 就在这里通过这个循环模拟一直等待消费.
        while (true) {
            Thread.sleep(500);
        }
    }
}

/*
 * 这个类用来表示一个生产者.
 * 通常这是一个单独的服务器程序.
 */
public class DemoProducer {
    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("启动生产者");
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("127.0.0.1");
        factory.setPort(9090);

        Connection connection = factory.newConnection();
        Channel channel = connection.createChannel();

        // 创建交换机和队列
        channel.exchangeDeclare("testExchange", ExchangeType.DIRECT, true, false, null);
        channel.queueDeclare("testQueue", true, false, false, null);

        // 创建一个消息并发送
        byte[] body = "hello".getBytes();
        boolean ok = channel.basicPublish("testExchange", "testQueue", null, body);
        System.out.println("消息投递完成! ok=" + ok);

        Thread.sleep(500);
        channel.close();
        connection.close();
    }
}

扩展功能

• 虚拟主机管理
• ⽤⼾管理/⽤⼾认证
• 交换机/队列 的独占模式和⾃动删除.
• 发送⽅确认(broker 给⽣产者的确认应答)
• 拒绝应答 (nack)
• 死信队列
• 管理接⼝
• 管理⻚⾯