七、RabbitMQ-客户端源码之AMQPImpl+Method

作者：朱小厮 | 出自：https://hiddenpps.blog.csdn.net/column/info/14800

AMQPImpl类包括AMQP接口（public class AMQImpl implements AMQP）主要囊括了AMQP协议中的通信帧的类别。

这里以Connection.Start帧做一个例子。

public static class Connection {
    public static final int INDEX = 10;
    public static class Start
        extends Method
        implements com.rabbitmq.client.AMQP.Connection.Start
    {
        public static final int INDEX = 10;
        private final int versionMajor;
        private final int versionMinor;
        private final Map
   
     
      
     serverProperties;
        private final LongString mechanisms;
        private final LongString locales;
....//下面省略很多代码。。。
   
     

可以看到Start类是Connection类的内部静态子类，表示此Start类为Connection.Start，而且Start类是继承Method方法的，包括接下来所有的AMQP协议帧都是继承这个Method方法，Method可以看成用来区分AMQP协议帧的类型。

Method类是一个抽象类(Base class for AMQP method objects, specialized by autogenerated code in AMQP.java)，我们来看下Method类的代码：

public abstract class Method implements com.rabbitmq.client.Method {
    /** {@inheritDoc} */
    public abstract int protocolClassId(); /* properly an unsigned short */
    /** {@inheritDoc} */
    public abstract int protocolMethodId(); /* properly an unsigned short */
    /** {@inheritDoc} */
    public abstract String protocolMethodName();
    /**
     * Tell if content is present.
     * @return true if the wire-protocol for this method should involve a content header and body,
     * or false if it should just involve a single method frame.
     */
    public abstract boolean hasContent();
    /**
     * Visitor support (double-dispatch mechanism).
     * @param visitor the visitor object
     * @return the result of the "visit" operation
     * @throws IOException if an error is encountered
     */
    public abstract Object visit(MethodVisitor visitor) throws IOException;
    /**
     * Private API - Autogenerated writer for this method.
     * @param writer interface to an object to write the method arguments
     * @throws IOException if an error is encountered
     */
    public abstract void writeArgumentsTo(MethodArgumentWriter writer) throws IOException;
    /**
     * Public API - debugging utility
     * @param buffer the buffer to append debug data to
     */
    public void appendArgumentDebugStringTo(StringBuilder buffer) {
        buffer.append("(?)");
    }
    @Override public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("#method<").append(protocolMethodName()).append(">");
        this.appendArgumentDebugStringTo(sb);
        return sb.toString();
    }
    public Frame toFrame(int channelNumber) throws IOException {
        Frame frame = new Frame(AMQP.FRAME_METHOD, channelNumber);
        DataOutputStream bodyOut = frame.getOutputStream();
        bodyOut.writeShort(protocolClassId());
        bodyOut.writeShort(protocolMethodId());
        MethodArgumentWriter argWriter = new MethodArgumentWriter(new ValueWriter(bodyOut));
        writeArgumentsTo(argWriter);
        argWriter.flush();
        return frame;
    }

代码不长。挑几个解释下。

protocolClassId()和protocolMethodId()：每一个Method（Connection.Start/.StartOk, Connection.Tune/.TuneOk等等）都包含classId和methodId,可以参考下图：

 

protocolMethodName()返回本Method的名称，比如Connection.Start的就是：

public String protocolMethodName() { return "connection.start";}

boolean hasContent()用来区分这个Method之后是否有Content-Body,比如Connection.Start的为：

public boolean hasContent() { return false; }

又比如Basic.Publish的为：

public boolean hasContent() { return true; }

---

好了，这里可以回来接着讲AMQPImpl了。

下面是一张表，用来涵盖AQMP协议各个种类的Method以及其一些属性，看完这张表就看完了AMQPImpl的全部。

Method-Name	classId	methodId	hasContent
Connection.Start	10	10	false
Connection.StartOk	10	11	false
Connection.Secure	10	20	false
Connection.SecureOk	10	21	false
Connection.Tune	10	30	false
Connection.TuneOk	10	31	false
Connection.Open	10	40	false
Connection.OpenOk	10	41	false
Connection.Close	10	50	false
Connection.CloseOk	10	51	false
Connection.Blocked	10	60	false
Connection.Unblocked	10	61	false
Channel.Open	20	10	false
Channel.OpenOk	20	11	false
Channel.Flow	20	20	false
Channel.FlowOk	20	21	false
Channel.Close	20	40	false
Channel.CloseOk	20	41	false
Access.Request	30	10	false
Access.RequestOk	30	11	false
Exchange.Declare	40	10	false
Exchange.DeclareOk	40	11	false
Exchange.Delete	40	20	false
Exchange.DeleteOk	40	21	false
Exchange.Bind	40	30	false
Exchange.BindOk	40	31	false
Exchange.Unbind	40	40	false
Exchange.UnbindOk	40	51	false
Queue.Declare	50	10	false
Queue.DeclareOk	50	11	false
Queue.Bind	50	20	false
Queue.BindOk	50	21	false
Queue.Purge	50	30	false
Queue.PurgeOk	50	31	false
Queue.Delete	50	40	false
Queue.DeleteOk	50	41	false
Queue.Unbind	50	50	false
Queue.UnbindOk	50	51	false
Basic.Qos	60	10	false
Basic.QosOk	60	11	false
Basic.Consume	60	20	false
Basic.ConsumeOk	60	21	false
Basic.Cancel	60	30	false
Basic.CancelOk	60	31	false
Basic.Publish	60	40	true
Basic.Return	60	50	true
Basic.Deliver	60	60	true
Basic.Get	60	70	false
Basic.GetOk	60	71	true
Basic.GetEmpty	60	72	false
Basic.Ack	60	80	false
Basic.Reject	60	90	false
Basic.RecoverAsync	60	100	false
Basic.Recover	60	110	false
Basic.RecoverOk	60	111	false
Basic.Nack	60	120	false
Tx.Select	90	10	false
Tx.SelectOk	90	11	false
Tx.Commit	90	20	false
Tx.CommitOk	90	21	false
Tx.Rollback	90	30	false
Tx.RollbackOk	90	31	false
Confirm.Select	85	10	false
Confirm.SelectOk	85	11	false