[七]RabbitMQ-客户端源码之AMQPImpl+Method

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<String,Object> 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; }

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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

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附：本系列全集

1. [Conclusion]RabbitMQ-客户端源码之总结
2. [一]RabbitMQ-客户端源码之ConnectionFactory
3. [二]RabbitMQ-客户端源码之AMQConnection
4. [三]RabbitMQ-客户端源码之ChannelManager
5. [四]RabbitMQ-客户端源码之Frame
6. [五]RabbitMQ-客户端源码之AMQChannel
7. [六]RabbitMQ-客户端源码之AMQCommand
8. [七]RabbitMQ-客户端源码之AMQPImpl+Method
9. [八]RabbitMQ-客户端源码之ChannelN
10. [九]RabbitMQ-客户端源码之Consumer

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