org.eclipse.paho.client.mqttv3.internal.wire :

                 MQTT协议中报文信息，里面包含有心跳包、订阅包、发布包、确认包等。

1、MqttWireMessage源码

package com.miller.springcloudkebeedgeprotocol.coap;

/**
 * @program: spring-cloud-kubeedge
 * @description: ymfx
 * @author: Miller.FAN
 * @create: 2019-12-10 16:16
 **/

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttPersistable;
import org.eclipse.paho.client.mqttv3.MqttToken;
import org.eclipse.paho.client.mqttv3.internal.ExceptionHelper;
import org.eclipse.paho.client.mqttv3.internal.wire.*;

public abstract class MqttWireMessage {
    //MQTT数据包类型定义
    public static final byte MESSAGE_TYPE_CONNECT = 1;
    public static final byte MESSAGE_TYPE_CONNACK = 2;
    public static final byte MESSAGE_TYPE_PUBLISH = 3;
    public static final byte MESSAGE_TYPE_PUBACK = 4;
    public static final byte MESSAGE_TYPE_PUBREC = 5;
    public static final byte MESSAGE_TYPE_PUBREL = 6;
    public static final byte MESSAGE_TYPE_PUBCOMP = 7;
    public static final byte MESSAGE_TYPE_SUBSCRIBE = 8;
    public static final byte MESSAGE_TYPE_SUBACK = 9;
    public static final byte MESSAGE_TYPE_UNSUBSCRIBE = 10;
    public static final byte MESSAGE_TYPE_UNSUBACK = 11;
    public static final byte MESSAGE_TYPE_PINGREQ = 12;
    public static final byte MESSAGE_TYPE_PINGRESP = 13;
    public static final byte MESSAGE_TYPE_DISCONNECT = 14;

    protected static final Charset STRING_ENCODING;
    private static final String[] PACKET_NAMES;

    private static final long FOUR_BYTE_INT_MAX = 4294967295L;

    private static final int VARIABLE_BYTE_INT_MAX = 268435455;
    private byte type;
    protected int msgId;
    protected boolean duplicate = false;
    private MqttToken token;
    //静态块  加载类之前执行，只执行一次  我理解这部分代码执行完毕会在常量池中生成相关的常量信息
    static {
        STRING_ENCODING = StandardCharsets.UTF_8;
        PACKET_NAMES = new String[]{"reserved", "CONNECT", "0", "PUBLISH", "PUBACK", "PUBREC", "PUBREL", "PUBCOMP", "SUBSCRIBE", "SUBACK", "UNSUBSCRIBE", "UNSUBACK", "PINGREQ", "PINGRESP", "DISCONNECT"};
    }

    //构造器 参数是：消息类型
    public MqttWireMessage(byte type) {
        this.type = type;
        this.msgId = 0;
    }
    //抽象方法 获取信息详情
    protected abstract byte getMessageInfo();

    // 获取消息体
    public byte[] getPayload() throws MqttException {
        return new byte[0];
    }

    //获取消息类型
    public byte getType() {
        return this.type;
    }

    //获取消息的id
    public int getMessageId() {
        return this.msgId;
    }
    //
    public void setMessageId(int msgId) {
        this.msgId = msgId;
    }
    //
    public String getKey() {
        return Integer.toString(this.getMessageId());
    }
    //获取 头信息 抽象方法
    public byte[] getHeader() throws MqttException {
        try {
            int first = (this.getType() & 15) << 4 ^ this.getMessageInfo() & 15;
            byte[] varHeader = this.getVariableHeader();
            int remLen = varHeader.length + this.getPayload().length;
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            DataOutputStream dos = new DataOutputStream(baos);
            dos.writeByte(first);
            dos.write(encodeMBI((long)remLen));
            dos.write(varHeader);
            dos.flush();
            return baos.toByteArray();
        } catch (IOException var6) {
            throw new MqttException(var6);
        }
    }
    //抽象方法
    protected abstract byte[] getVariableHeader() throws MqttException;

    public boolean isMessageIdRequired() {
        return true;
    }

    //新建一个消息  如果传入的消息体是空，给一个new byte[0];
    public static org.eclipse.paho.client.mqttv3.internal.wire.MqttWireMessage createWireMessage(MqttPersistable data) throws MqttException {
        byte[] payload = data.getPayloadBytes();
        if (payload == null) {
            //防止 null
            payload = new byte[0];
        }

        MultiByteArrayInputStream mbais = new MultiByteArrayInputStream(data.getHeaderBytes(), data.getHeaderOffset(), data.getHeaderLength(), payload, data.getPayloadOffset(), data.getPayloadLength());
        return createWireMessage((InputStream)mbais);
    }

    public static org.eclipse.paho.client.mqttv3.internal.wire.MqttWireMessage createWireMessage(byte[] bytes) throws MqttException {
        ByteArrayInputStream bais = new ByteArrayInputStream(bytes);
        return createWireMessage((InputStream)bais);
    }
    //这个是私有函数体
    private static org.eclipse.paho.client.mqttv3.internal.wire.MqttWireMessage createWireMessage(InputStream inputStream) throws MqttException {
        try {
            //统计输入流中字节数
            CountingInputStream counter = new CountingInputStream(inputStream);
            //
            DataInputStream in = new DataInputStream(counter);
            //the next byte of this input stream, interpreted as an unsigned 8-bit number.
            int first = in.readUnsignedByte();
            //取得消息类型
            byte type = (byte)(first >> 4);
            //我觉得这是编程习惯，严谨一些，不执行这一步一样可以
            byte info = (byte)(first &= 15);

            long remLen = (long)readMBI(in).getValue();

            long totalToRead = (long)counter.getCounter() + remLen;

            //剩余多大空间
            long remainder = totalToRead - (long)counter.getCounter();

            byte[] data = new byte[0];

            if (remainder > 0L) {
                data = new byte[(int)remainder];
                in.readFully(data, 0, data.length);
            }
            //按照消息类型 组合消息头和消息体 生成的包不一样
            Object result;
            if (type == 1) {
                result = new MqttConnect(info, data);
            } else if (type == 3) {
                result = new MqttPublish(info, data);
            } else if (type == 4) {
                result = new MqttPubAck(info, data);
            } else if (type == 7) {
                result = new MqttPubComp(info, data);
            } else if (type == 2) {
                result = new MqttConnack(info, data);
            } else if (type == 12) {
                result = new MqttPingReq(info, data);
            } else if (type == 13) {
                result = new MqttPingResp(info, data);
            } else if (type == 8) {
                result = new MqttSubscribe(info, data);
            } else if (type == 9) {
                result = new MqttSuback(info, data);
            } else if (type == 10) {
                result = new MqttUnsubscribe(info, data);
            } else if (type == 11) {
                result = new MqttUnsubAck(info, data);
            } else if (type == 6) {
                result = new MqttPubRel(info, data);
            } else if (type == 5) {
                result = new MqttPubRec(info, data);
            } else {
                if (type != 14) {
                    throw ExceptionHelper.createMqttException(6);
                }
                // type = 14 的情况
                result = new MqttDisconnect(info, data);
            }

            return (org.eclipse.paho.client.mqttv3.internal.wire.MqttWireMessage)result;
        } catch (IOException var14) {
            throw new MqttException(var14);
        }
    }

    // 输入一个long 类型的数，返回一个byte数组
    public static byte[] encodeMBI(long number) {
        // 检查 number 是不是在规定的范围之内
        validateVariableByteInt((int)number);
        //局部变量
        int numBytes = 0;
        long no = number;
        //字节码输出流
        ByteArrayOutputStream bos = new ByteArrayOutputStream();

        do {
            byte digit = (byte)((int)(no % 128L));
            no /= 128L;
            if (no > 0L) {
                digit = (byte)(digit | 128);
            }

            bos.write(digit);
            ++numBytes;
        } while(no > 0L && numBytes < 4);

        return bos.toByteArray();
    }
    //类型转化
    public static MultiByteInteger readMBI(DataInputStream in) throws IOException {
        int msgLength = 0;
        int multiplier = 1;
        int count = 0;

        byte digit;
        do {
            digit = in.readByte();
            ++count;
            msgLength += (digit & 127) * multiplier;
            multiplier *= 128;
        } while((digit & 128) != 0);

        if (msgLength >= 0 && msgLength <= 268435455) {
            return new MultiByteInteger(msgLength, count);
        } else {
            throw new IOException("This property must be a number between 0 and 268435455. Read value was: " + msgLength);
        }
    }

    protected byte[] encodeMessageId() throws MqttException {
        try {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            DataOutputStream dos = new DataOutputStream(baos);
            dos.writeShort(this.msgId);
            dos.flush();
            return baos.toByteArray();
        } catch (IOException var3) {
            throw new MqttException(var3);
        }
    }

    public boolean isRetryable() {
        return false;
    }

    public void setDuplicate(boolean duplicate) {
        this.duplicate = duplicate;
    }

    public static void encodeUTF8(DataOutputStream dos, String stringToEncode) throws MqttException {
        validateUTF8String(stringToEncode);

        try {
            byte[] encodedString = stringToEncode.getBytes(STRING_ENCODING);
            byte byte1 = (byte)(encodedString.length >>> 8 & 255);
            byte byte2 = (byte)(encodedString.length >>> 0 & 255);
            dos.write(byte1);
            dos.write(byte2);
            dos.write(encodedString);
        } catch (UnsupportedEncodingException var5) {
            throw new MqttException(var5);
        } catch (IOException var6) {
            throw new MqttException(var6);
        }
    }

    public static String decodeUTF8(DataInputStream input) throws MqttException {
        try {
            int encodedLength = input.readUnsignedShort();
            byte[] encodedString = new byte[encodedLength];
            input.readFully(encodedString);
            String output = new String(encodedString, STRING_ENCODING);
            validateUTF8String(output);
            return output;
        } catch (IOException var4) {
            throw new MqttException(var4);
        }
    }

    private static void validateUTF8String(String input) throws IllegalArgumentException {
        for(int i = 0; i < input.length(); ++i) {
            boolean isBad = false;
            char c = input.charAt(i);
            if (Character.isHighSurrogate(c)) {
                ++i;
                if (i == input.length()) {
                    isBad = true;
                } else {
                    char c2 = input.charAt(i);
                    if (Character.isLowSurrogate(c2)) {
                        isBad = true;
                    } else {
                        int ch = (c & 1023) << 10 | c2 & 1023;
                        if ((ch & '\uffff') == 65535 || (ch & '\uffff') == 65534) {
                            isBad = true;
                        }
                    }
                }
            } else if (!Character.isISOControl(c) && !Character.isLowSurrogate(c)) {
                if (c >= '\ufdd0' && (c == '\ufffe' || c >= '\ufdd0' || c <= '\ufddf')) {
                    isBad = true;
                }
            } else {
                isBad = true;
            }

            if (isBad) {
                throw new IllegalArgumentException(String.format("Invalid UTF-8 char: [%x]", Integer.valueOf(c)));
            }
        }

    }
    // 检查int value 是不是在规定的范围之内
    public static void validateVariableByteInt(int value) throws IllegalArgumentException {
        if (value < 0 || value > 268435455) {
            throw new IllegalArgumentException("This property must be a number between 0 and 268435455");
        }
    }

    public MqttToken getToken() {
        return this.token;
    }

    public void setToken(MqttToken token) {
        this.token = token;
    }

    public String toString() {
        return PACKET_NAMES[this.type];
    }
}

消息流：

Token类的实现

import org.eclipse.paho.client.mqttv3.IMqttActionListener;
import org.eclipse.paho.client.mqttv3.IMqttAsyncClient;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.internal.ExceptionHelper;
import org.eclipse.paho.client.mqttv3.internal.wire.MqttAck;
import org.eclipse.paho.client.mqttv3.internal.wire.MqttConnack;
import org.eclipse.paho.client.mqttv3.internal.wire.MqttSuback;
import org.eclipse.paho.client.mqttv3.internal.wire.MqttWireMessage;
import org.eclipse.paho.client.mqttv3.logging.Logger;
import org.eclipse.paho.client.mqttv3.logging.LoggerFactory;

public class Token {
    //如此写法有什么好处？ final 修饰，常量，类加载后 CLASS_NAME 被保存到常量池中 ，但是该处使用反射得到类名 主动加载
    private static final String CLASS_NAME = org.eclipse.paho.client.mqttv3.internal.Token.class.getName();
    private Logger log;
    private volatile boolean completed;
    private boolean pendingComplete;
    private boolean sent;
    private Object responseLock;
    private Object sentLock;
    protected MqttMessage message;
    private MqttWireMessage response;
    private MqttException exception;
    private String[] topics;
    private String key;
    private IMqttAsyncClient client;
    private IMqttActionListener callback;
    private Object userContext;
    private int messageID;
    private boolean notified;

    public Token(String logContext) {
        this.log = LoggerFactory.getLogger("org.eclipse.paho.client.mqttv3.internal.nls.logcat", CLASS_NAME);
        this.completed = false;
        this.pendingComplete = false;
        this.sent = false;
        this.responseLock = new Object();
        this.sentLock = new Object();
        this.message = null;
        this.response = null;
        this.exception = null;
        this.topics = null;
        this.client = null;
        this.callback = null;
        this.userContext = null;
        this.messageID = 0;
        this.notified = false;
        this.log.setResourceName(logContext);
    }

    public int getMessageID() {
        return this.messageID;
    }

    public void setMessageID(int messageID) {
        this.messageID = messageID;
    }

    public boolean checkResult() throws MqttException {
        if (this.getException() != null) {
            throw this.getException();
        } else {
            return true;
        }
    }

    public MqttException getException() {
        return this.exception;
    }

    public boolean isComplete() {
        return this.completed;
    }

    protected boolean isCompletePending() {
        return this.pendingComplete;
    }

    protected boolean isInUse() {
        return this.getClient() != null && !this.isComplete();
    }

    public void setActionCallback(IMqttActionListener listener) {
        this.callback = listener;
    }

    public IMqttActionListener getActionCallback() {
        return this.callback;
    }

    public void waitForCompletion() throws MqttException {
        this.waitForCompletion(-1L);
    }

    public void waitForCompletion(long timeout) throws MqttException {
        String methodName = "waitForCompletion";
        this.log.fine(CLASS_NAME, "waitForCompletion", "407", new Object[]{this.getKey(), timeout, this});
        MqttWireMessage resp = this.waitForResponse(timeout);
        if (resp == null && !this.completed) {
            this.log.fine(CLASS_NAME, "waitForCompletion", "406", new Object[]{this.getKey(), this});
            this.exception = new MqttException(32000);
            throw this.exception;
        } else {
            this.checkResult();
        }
    }

    protected MqttWireMessage waitForResponse() throws MqttException {
        return this.waitForResponse(-1L);
    }

    protected MqttWireMessage waitForResponse(long timeout) throws MqttException {
        String methodName = "waitForResponse";
        synchronized(this.responseLock) {
            this.log.fine(CLASS_NAME, "waitForResponse", "400", new Object[]{this.getKey(), timeout, this.sent, this.completed, this.exception == null ? "false" : "true", this.response, this}, this.exception);

            while(!this.completed) {
                if (this.exception == null) {
                    try {
                        this.log.fine(CLASS_NAME, "waitForResponse", "408", new Object[]{this.getKey(), new Long(timeout)});
                        if (timeout <= 0L) {
                            this.responseLock.wait();
                        } else {
                            this.responseLock.wait(timeout);
                        }
                    } catch (InterruptedException var6) {
                        this.exception = new MqttException(var6);
                    }
                }

                if (!this.completed) {
                    if (this.exception != null) {
                        this.log.fine(CLASS_NAME, "waitForResponse", "401", (Object[])null, this.exception);
                        throw this.exception;
                    }

                    if (timeout > 0L) {
                        break;
                    }
                }
            }
        }

        this.log.fine(CLASS_NAME, "waitForResponse", "402", new Object[]{this.getKey(), this.response});
        return this.response;
    }

    protected void markComplete(MqttWireMessage msg, MqttException ex) {
        String methodName = "markComplete";
        this.log.fine(CLASS_NAME, "markComplete", "404", new Object[]{this.getKey(), msg, ex});
        synchronized(this.responseLock) {
            if (msg instanceof MqttAck) {
                this.message = null;
            }

            this.pendingComplete = true;
            this.response = msg;
            this.exception = ex;
        }
    }

    protected void notifyComplete() {
        String methodName = "notifyComplete";
        this.log.fine(CLASS_NAME, "notifyComplete", "404", new Object[]{this.getKey(), this.response, this.exception});
        synchronized(this.responseLock) {
            if (this.exception == null && this.pendingComplete) {
                this.completed = true;
                this.pendingComplete = false;
            } else {
                this.pendingComplete = false;
            }

            this.responseLock.notifyAll();
        }

        synchronized(this.sentLock) {
            this.sent = true;
            this.sentLock.notifyAll();
        }
    }

    public void waitUntilSent() throws MqttException {
        String methodName = "waitUntilSent";
        synchronized(this.sentLock) {
            synchronized(this.responseLock) {
                if (this.exception != null) {
                    throw this.exception;
                }
            }

            while(!this.sent) {
                try {
                    this.log.fine(CLASS_NAME, "waitUntilSent", "409", new Object[]{this.getKey()});
                    this.sentLock.wait();
                } catch (InterruptedException var4) {
                }
            }

            if (!this.sent) {
                if (this.exception == null) {
                    throw ExceptionHelper.createMqttException(6);
                } else {
                    throw this.exception;
                }
            }
        }
    }

    protected void notifySent() {
        String methodName = "notifySent";
        this.log.fine(CLASS_NAME, "notifySent", "403", new Object[]{this.getKey()});
        synchronized(this.responseLock) {
            this.response = null;
            this.completed = false;
        }

        synchronized(this.sentLock) {
            this.sent = true;
            this.sentLock.notifyAll();
        }
    }

    public IMqttAsyncClient getClient() {
        return this.client;
    }

    protected void setClient(IMqttAsyncClient client) {
        this.client = client;
    }

    public void reset() throws MqttException {
        String methodName = "reset";
        if (this.isInUse()) {
            throw new MqttException(32201);
        } else {
            this.log.fine(CLASS_NAME, "reset", "410", new Object[]{this.getKey()});
            this.client = null;
            this.completed = false;
            this.response = null;
            this.sent = false;
            this.exception = null;
            this.userContext = null;
        }
    }

    public MqttMessage getMessage() {
        return this.message;
    }

    public MqttWireMessage getWireMessage() {
        return this.response;
    }

    public void setMessage(MqttMessage msg) {
        this.message = msg;
    }

    public String[] getTopics() {
        return this.topics;
    }

    public void setTopics(String[] topics) {
        this.topics = (String[])topics.clone();
    }

    public Object getUserContext() {
        return this.userContext;
    }

    public void setUserContext(Object userContext) {
        this.userContext = userContext;
    }

    public void setKey(String key) {
        this.key = key;
    }

    public String getKey() {
        return this.key;
    }

    public void setException(MqttException exception) {
        synchronized(this.responseLock) {
            this.exception = exception;
        }
    }

    public boolean isNotified() {
        return this.notified;
    }

    public void setNotified(boolean notified) {
        this.notified = notified;
    }

    public String toString() {
        StringBuffer tok = new StringBuffer();
        tok.append("key=").append(this.getKey());
        tok.append(" ,topics=");
        if (this.getTopics() != null) {
            for(int i = 0; i < this.getTopics().length; ++i) {
                tok.append(this.getTopics()[i]).append(", ");
            }
        }

        tok.append(" ,usercontext=").append(this.getUserContext());
        tok.append(" ,isComplete=").append(this.isComplete());
        tok.append(" ,isNotified=").append(this.isNotified());
        tok.append(" ,exception=").append(this.getException());
        tok.append(" ,actioncallback=").append(this.getActionCallback());
        return tok.toString();
    }

    public int[] getGrantedQos() {
        int[] val = new int[0];
        if (this.response instanceof MqttSuback) {
            val = ((MqttSuback)this.response).getGrantedQos();
        }

        return val;
    }

    public boolean getSessionPresent() {
        boolean val = false;
        if (this.response instanceof MqttConnack) {
            val = ((MqttConnack)this.response).getSessionPresent();
        }

        return val;
    }

    public MqttWireMessage getResponse() {
        return this.response;
    }
}