rabbitmq学习7:ConntectionFactory与Conntection的认知

从前面几小节的学习，我们可能知道在发送和接收消息重要的类ConnectionFactory， Connection，Channel和QueueingConsumer。

  ConntectionFactory类是方便创建与AMQP代理相关联的Connection；下面来看看ConntectionFactory是如何创建一个Contention.

  首先通过new ConnectionFactory()创建一个ConnectionFactory；并设置此连接工厂的主机设置为localhost。通过ConnectionFactory的newConnection()方法 创建一个Connection; newConnection方法通过得到当前连接的地址及端口号来获得一个Address，通过createFrameHandler的方法 来得到FrameHandler;再通过new AMQConnection(this, frameHandler)来得到Connection并启动。如代码清单7-1所示。

    代码清单7-1 创建Connection的源码（ConnectionFactory.java中）

 

 1. protected FrameHandler createFrameHandler(Address addr)
 2.         throws IOException {
 3.
 4.         String hostName = addr.getHost();
 5.         int portNumber = portOrDefault(addr.getPort());//得到端口号
 6.         Socket socket = factory.createSocket();
 7.         configureSocket(socket);//这里Socket通过TCP无迟延的协议
 8.         socket.connect(new InetSocketAddress(hostName, portNumber), connectionTimeout);
 9.         return createFrameHandler(socket);
10.     }
11.
12.     protected FrameHandler createFrameHandler(Socket sock)
13.         throws IOException
14.     {
15.         return new SocketFrameHandler(sock);
16.     }
17.
18.     /**
19.      *  Provides a hook to insert custom configuration of the sockets
20.      *  used to connect to an AMQP server before they connect.
21.      *
22.      *  The default behaviour of this method is to disable Nagle's
23.      *  algorithm to get more consistently low latency.  However it
24.      *  may be overridden freely and there is no requirement to retain
25.      *  this behaviour.
26.      *
27.      *  @param socket The socket that is to be used for the Connection
28.      */
29.     protected void configureSocket(Socket socket) throws IOException{
30.         // disable Nagle's algorithm, for more consistently low latency
31.         socket.setTcpNoDelay(true);
32.     }
33.
34.     /**
35.      * Create a new broker connection
36.      * @param addrs an array of known broker addresses (hostname/port pairs) to try in order
37.      * @return an interface to the connection
38.      * @throws IOException if it encounters a problem
39.      */
40.     public Connection newConnection(Address[] addrs)
41.         throws IOException
42.     {
43.         IOException lastException = null;
44.         for (Address addr : addrs) {
45.             try {
46.                 FrameHandler frameHandler = createFrameHandler(addr);
47.                 AMQConnection conn = new AMQConnection(this,
48.                                                        frameHandler);
49.                 conn.start();
50.                 return conn;
51.             } catch (IOException e) {
52.                 lastException = e;
53.             }
54.         }
55.
56.         if (lastException == null) {
57.             throw new IOException("failed to connect");
58.         } else {
59.             throw lastException;
60.         }
61.     }
62.
63.     /**
64.      * Create a new broker connection
65.      * @return an interface to the connection
66.      * @throws IOException if it encounters a problem
67.      */
68.     public Connection newConnection() throws IOException {
69.         return newConnection(new Address[] {
70.                                  new Address(getHost(), getPort())});
71.     }

 

代码清单7-2 连接启动

 

/**
     * Start up the connection, including the MainLoop thread.
     * Sends the protocol
     * version negotiation header, and runs through
     * Connection.Start/.StartOk, Connection.Tune/.TuneOk, and then
     * calls Connection.Open and waits for the OpenOk. Sets heartbeat
     * and frame max values after tuning has taken place.
     * @throws java.io.IOException if an error is encountered; IOException
     * subtypes {@link ProtocolVersionMismatchException} and
     * {@link PossibleAuthenticationFailureException} will be thrown in the
     * corresponding circumstances.
     */
    public void start()
        throws IOException
    {
        // Make sure that the first thing we do is to send the header,
        // which should cause any socket errors to show up for us, rather
        // than risking them pop out in the MainLoop
        AMQChannel.SimpleBlockingRpcContinuation connStartBlocker =
            new AMQChannel.SimpleBlockingRpcContinuation();
        // We enqueue an RPC continuation here without sending an RPC
        // request, since the protocol specifies that after sending
        // the version negotiation header, the client (connection
        // initiator) is to wait for a connection.start method to
        // arrive.
        _channel0.enqueueRpc(connStartBlocker);
        // The following two lines are akin to AMQChannel's
        // transmit() method for this pseudo-RPC.
        _frameHandler.setTimeout(HANDSHAKE_TIMEOUT);
        _frameHandler.sendHeader();

        // start the main loop going
        Thread ml = new MainLoop();
        ml.setName("AMQP Connection " + getHostAddress() + ":" + getPort());
        ml.start();

        AMQP.Connection.Start connStart = null;
        try {
            connStart =
                (AMQP.Connection.Start) connStartBlocker.getReply().getMethod();

            _serverProperties = connStart.getServerProperties();

            Version serverVersion =
                new Version(connStart.getVersionMajor(),
                            connStart.getVersionMinor());

            if (!Version.checkVersion(clientVersion, serverVersion)) {
                _frameHandler.close(); //this will cause mainLoop to terminate
                throw new ProtocolVersionMismatchException(clientVersion,
                                                           serverVersion);
            }
        } catch (ShutdownSignalException sse) {
            throw AMQChannel.wrap(sse);
        }

        String[] mechanisms = connStart.getMechanisms().toString().split(" ");
        SaslMechanism sm = _factory.getSaslConfig().getSaslMechanism(mechanisms);
        if (sm == null) {
            throw new IOException("No compatible authentication mechanism found - " +
                    "server offered [" + connStart.getMechanisms() + "]");
        }

        LongString challenge = null;
        LongString response = sm.handleChallenge(null, _factory);

        AMQP.Connection.Tune connTune = null;
        do {
            Method method = (challenge == null)
                ? new AMQImpl.Connection.StartOk(_clientProperties,
                                                 sm.getName(),
                                                 response, "en_US")
                : new AMQImpl.Connection.SecureOk(response);

            try {
                Method serverResponse = _channel0.rpc(method).getMethod();
                if (serverResponse instanceof AMQP.Connection.Tune) {
                    connTune = (AMQP.Connection.Tune) serverResponse;
                } else {
                    challenge = ((AMQP.Connection.Secure) serverResponse).getChallenge();
                    response = sm.handleChallenge(challenge, _factory);
                }
            } catch (ShutdownSignalException e) {
                throw new PossibleAuthenticationFailureException(e);
            }
        } while (connTune == null);

        int channelMax =
            negotiatedMaxValue(_factory.getRequestedChannelMax(),
                               connTune.getChannelMax());
        _channelManager = new ChannelManager(channelMax);

        int frameMax =
            negotiatedMaxValue(_factory.getRequestedFrameMax(),
                               connTune.getFrameMax());
        setFrameMax(frameMax);

        int heartbeat =
            negotiatedMaxValue(_factory.getRequestedHeartbeat(),
                               connTune.getHeartbeat());
        setHeartbeat(heartbeat);

        _channel0.transmit(new AMQImpl.Connection.TuneOk(channelMax,
                                                         frameMax,
                                                         heartbeat));
        // 0.9.1: insist [on not being redirected] is deprecated, but
        // still in generated code; just pass a dummy value here
        _channel0.exnWrappingRpc(new AMQImpl.Connection.Open(_virtualHost,
                                                            "",
                                                            false)).getMethod();
        return;
    }