带你手写基于 Spring 的可插拔式 RPC 框架（三）通信协议模块

在写代码之前我们先要想清楚几个问题。

我们的框架到底要实现什么功能？
我们要实现一个远程调用的 RPC 协议。
最终实现效果是什么样的？
我们能像调用本地服务一样调用远程的服务。
怎样实现上面的效果？
前面几章已经给大家说了，使用动态代理，在客户端生成接口代理类使用，在代理类的 invoke 方法里面将方法参数等信息组装成 request 发给服务端，服务端需要起一个服务器一直等待接收这种消息，接收之后使用反射调
用对应接口的实现类。

首先我们需要实现底层的通信的服务端和客户端，可以有一下几种实现：

基于 Socket 的客户端和服务端（同步阻塞式，不推荐），大家可以当作一个编程练习，整个和系统没有进行整合，纯粹练习使用。
基于 Socket 的服务端。
启动一个阻塞式的 socket server，加入一个线程池实现伪异步。

public class SocketServer {

     private static SocketServer INSTANCE = new SocketServer();
 
     private SocketServer(){};
 
     public static SocketServer getInstance() {
         return INSTANCE;
     }
 
     //没有核心线程数量控制的线程池，最大线程数是 Integer 的最大值,多线程实现伪异步
     ExecutorService executorService = Executors.newCachedThreadPool();
 
     /**
      * 发布服务,bio 模型
      * @param service
      * @param port
      */
     public void publiser(int port){
         try (ServerSocket serverSocket  = new ServerSocket(port);)
         {
             while (true){
                 Socket socket = serverSocket.accept();//接收请求
                 executorService.execute(new SocketHandler(socket));
             }
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }

对应的 hanlder，使用反射调用对应的服务，并通过 sokcet 写回结果。

public class SocketHandler implements Runnable{
 
     private Socket socket;
 
     public SocketHandler(Socket socket) {
         this.socket = socket;
     }
 
     @Override
     public void run() {
         try (ObjectInputStream inputStream = new ObjectInputStream(socket.getInputStream());
              ObjectOutputStream outputStream = new ObjectOutputStream(socket.getOutputStream());)
         {
             Object o = inputStream.readObject(); //readObject 是 java 反序列化的过程
             System.out.println(o);
             Object result = invoke((RpcRequest) o);
             //写回结果
             outputStream.writeObject(result);
             outputStream.flush();
         } catch (IOException e) {
             e.printStackTrace();
         } catch (ClassNotFoundException e) {
             e.printStackTrace();
         }
     }
 
     private Object invoke(RpcRequest invocation){
 
         //根据方法名和参数类型在 service 里获取方法
         try {
             String interFaceName = invocation.getInterfaceName();
             Class impClass = Class.forName(invocation.getImpl());
 
             Method method = impClass.getMethod(invocation.getMethodName(),invocation.getParamTypes());
             String result = (String)method.invoke(impClass.newInstance(),invocation.getParams());
             return result;
         } catch (NoSuchMethodException e) {
             e.printStackTrace();
         } catch (IllegalAccessException e) {
             e.printStackTrace();
         } catch (InvocationTargetException e) {
             e.printStackTrace();
         } catch (InstantiationException e) {
             e.printStackTrace();
         } catch (ClassNotFoundException e) {
             e.printStackTrace();
         }
 
         return null;
     }
 }

在看客户端，拼装参数，发送给 socket 服务端。

public class SocketClient {

     private static SocketClient INSTANCE = new SocketClient();
 
     private SocketClient(){};
 
     public static SocketClient getInstance() {
         return INSTANCE;
     }
 
     private Socket newSocket(String host, Integer port) {
         System.out.println("创建一个新的 socket 连接");
         try {
             Socket socket = new Socket(host, port);
             return socket;
         } catch (IOException e) {
             System.out.println("建立连接失败");
             e.printStackTrace();
         }
         return null;
     }
 
     public Object sendRequest(String host, Integer port,RpcRequest rpcRequest) {
         Socket socket = newSocket(host,port);
         try (
             ObjectOutputStream outputStream = new ObjectOutputStream(socket.getOutputStream());
             ObjectInputStream inputStream = new ObjectInputStream(socket.getInputStream());)
         {
             outputStream.writeObject(rpcRequest);
             outputStream.flush();
 
 
             Object result = inputStream.readObject();
 
             inputStream.close();
             outputStream.close();
             return result;
 
         } catch (Exception e) {
             e.printStackTrace();
         }
         return null;
     }
 }

通过上面的代码相信大家已经明白了这个流程了，就是一个客户端与服务端通信的过程，将需要调用的方法的参数传到服务端，服务端通过反射完成调用，最后返回结果给客户端。
下面正式开始。

基于 Http 请求的客户端和基于 Tomcat 的服务端。
基于 Tomcat 的服务端，单例模式，只有一个启动服务的 start 方法，监听到的请求通过 DispatcherServlet 处理。

public class HttpServer {

     private static HttpServer INSTANCE = new HttpServer();
     
     private HttpServer(){}
     
     public static HttpServer getInstance(){
         return INSTANCE;
     }
     
     
     /**
      *
      * servlet 容器，tomcat
      * @param hostname
      * @param port
      */
 
     public void start(String hostname,Integer port){
 
         Tomcat tomcat = new Tomcat();
         Server server = tomcat.getServer();
         Service service = server.findService("Tomcat");
 
         Connector connector = new Connector();
         connector.setPort(port);
 
         Engine engine = new StandardEngine();
         engine.setDefaultHost(hostname);
 
         Host host = new StandardHost();
         host.setName(hostname);
 
         String contextPath = "";
         Context context = new StandardContext();
         context.setPath(contextPath);
         context.addLifecycleListener(new Tomcat.FixContextListener()); //声明周期监听器
 
         host.addChild(context);
         engine.addChild(host);
 
         service.setContainer(engine);
         service.addConnector(connector);
 
         tomcat.addServlet(contextPath,"dispatcher", new DispatcherServlet());
         context.addServletMappingDecoded("/*","dispatcher");
 
         try {
             tomcat.start();
             tomcat.getServer().await();
         } catch (LifecycleException e) {
             e.printStackTrace();
         }
     }
 }

下面来看请求分发器 DispatcherServlet 的实现，将请求派发给 HttpServletHandler 实现。

/**
  * tomcat 是 servlet 容器，写一个 servlet
  *
  */
 public class DispatcherServlet extends HttpServlet {
 
     @Override
     protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         new HttpServletHandler().handler(req,resp);
     }
 }

HttpServletHandler 的实现其实就是解析 request，通过反射调用最后返回结果。

public class HttpServletHandler{

     public void handler(HttpServletRequest req, HttpServletResponse resp) {
 
         try(InputStream inputStream = req.getInputStream();
             OutputStream outputStream =resp.getOutputStream();){
             ObjectInputStream ois = new ObjectInputStream(inputStream);
             RpcRequest invocation = (RpcRequest) ois.readObject();
 
             // 从注册中心根据接口，找接口的实现类
             String interFaceName = invocation.getInterfaceName();
             Class impClass = Class.forName(invocation.getImpl());
 
 
             Method method = impClass.getMethod(invocation.getMethodName(),invocation.getParamTypes());
             Object result = method.invoke(impClass.newInstance(),invocation.getParams());
 
             RpcResponse rpcResponse = new RpcResponse();
             rpcResponse.setResponseId(invocation.getRequestId());
             rpcResponse.setData(result);
             IOUtils.write(toByteArray(rpcResponse),outputStream);
         }catch (IOException e){
             e.printStackTrace();
         } catch (ClassNotFoundException e) {
             e.printStackTrace();
         } catch (NoSuchMethodException e) {
             e.printStackTrace();
         } catch (IllegalAccessException e) {
             e.printStackTrace();
         } catch (InvocationTargetException e) {
             e.printStackTrace();
         } catch (InstantiationException e) {
             e.printStackTrace();
         }
     }
 
     public byte[] toByteArray (Object obj) {
         byte[] bytes = null;
         ByteArrayOutputStream bos = new ByteArrayOutputStream();
         try {
             ObjectOutputStream oos = new ObjectOutputStream(bos);
             oos.writeObject(obj);
             oos.flush();
             bytes = bos.toByteArray ();
             oos.close();
             bos.close();
         } catch (IOException ex) {
             ex.printStackTrace();
         }
         return bytes;
     }
 
 }

最后来看客户端的实现，通过 post 方法发送数据，最后解析服务端返回的结果。

public class HttpClient {
 
     private static HttpClient INSTANCE = new HttpClient();
     
     private HttpClient(){}
     
     public static HttpClient getInstance(){
         return INSTANCE;
     }
 
     public Object post(String hostname, Integer port, RpcRequest invocation){
 
         try{
             URL url = new URL("http",hostname,port,"/");
             HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
 
             httpURLConnection.setRequestMethod("POST");
             httpURLConnection.setDoOutput(true);
 
             OutputStream outputStream = httpURLConnection.getOutputStream();
             ObjectOutputStream oos = new ObjectOutputStream(outputStream);
             oos.writeObject(invocation);
             oos.flush();
             oos.close();
 
             InputStream inputStream = httpURLConnection.getInputStream();
             RpcResponse rpcResponse =  (RpcResponse)toObject(IOUtils.toByteArray(inputStream));
             return rpcResponse.getData();
 
 
         } catch (MalformedURLException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
         return null;
 
     }
 
     public Object toObject (byte[] bytes) {
         Object obj = null;
         try {
             ByteArrayInputStream bis = new ByteArrayInputStream(bytes);
             ObjectInputStream ois = new ObjectInputStream (bis);
             obj = ois.readObject();
             ois.close();
             bis.close();
         } catch (IOException ex) {
             ex.printStackTrace();
         } catch (ClassNotFoundException ex) {
             ex.printStackTrace();
         }
         return obj;
     }
 }

Netty 模型的客户端和服务端。
基于 Netty 的服务端，里面的编码器和解码器是我们自己实现的，大家可以先用我注释掉的那部分，等我们写到编码解码器的时候再替换。

public class NettyServer {
 
     private static NettyServer INSTANCE = new NettyServer();
     
     private static Executor executor = Executors.newCachedThreadPool();
     
     private final static int MESSAGE_LENGTH = 4;
     
     private NettyServer(){};
 
     public static NettyServer getInstance(){
         return INSTANCE;
     }
 
 
     private SerializeType serializeType = SerializeType.queryByType(Configuration.getInstance().getSerialize());
     
     public static void submit(Runnable t){
         executor.execute(t);
     }
     
     public void start(String host, Integer port){
         EventLoopGroup bossGroup = new NioEventLoopGroup(1);
         EventLoopGroup workerGroup = new NioEventLoopGroup();
         
         try{
             final ServerBootstrap bootstrap = new ServerBootstrap();
             bootstrap.group(bossGroup,workerGroup)
             .channel(NioServerSocketChannel.class)
             .option(ChannelOption.SO_BACKLOG, 128)
             .childOption(ChannelOption.SO_KEEPALIVE, true)
             .childHandler(new ChannelInitializer<SocketChannel>(){
 
                 @Override
                 protected void initChannel(SocketChannel arg0) throws Exception {
                     ChannelPipeline pipeline = arg0.pipeline();
                      //ObjectDecoder的基类半包解码器LengthFieldBasedFrameDecoder的报文格式保持兼容。因为底层的父类LengthFieldBasedFrameDecoder
                     //的初始化参数即为super(maxObjectSize, 0, 4, 0, 4); 
 //                  pipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, NettyServer.MESSAGE_LENGTH, 0, NettyServer.MESSAGE_LENGTH));
                     //利用LengthFieldPrepender回填补充ObjectDecoder消息报文头
 //                  pipeline.addLast(new LengthFieldPrepender(NettyServer.MESSAGE_LENGTH));
 //                  pipeline.addLast(new ObjectEncoder());
                     //考虑到并发性能，采用weakCachingConcurrentResolver缓存策略。一般情况使用:cacheDisabled即可
 //                  pipeline.addLast(new ObjectDecoder(Integer.MAX_VALUE, ClassResolvers.weakCachingConcurrentResolver(this.getClass().getClassLoader())));
                     //注册解码器NettyDecoderHandler
                     pipeline.addLast(new NettyDecoderHandler(RpcRequest.class, serializeType));
                     //注册编码器NettyEncoderHandler
                     pipeline.addLast(new NettyEncoderHandler(serializeType));
                     pipeline.addLast("handler", new NettyServerHandler());
                     
                 }
                 
             });
             Channel channel = bootstrap.bind(host, port).sync().channel();
             System.out.println("Server start listen at " + port);
         }catch(Exception e){
             bossGroup.shutdownGracefully();
             workerGroup.shutdownGracefully();
         }
     }
     
 
 }

服务端对应的 handler，netty 都是这种 handler 模式，handler 里面也是将这个接收的 request 放入线程池中处理。

    public class NettyServerHandler extends SimpleChannelInboundHandler<RpcRequest> {
 
     private ChannelHandlerContext context;
 
 
     @Override
     protected void channelRead0(ChannelHandlerContext ctx, RpcRequest rpcRequest) throws Exception {
         System.out.println("server channelRead...");
         System.out.println(ctx.channel().remoteAddress() + "->server:" + rpcRequest.toString());
         InvokeTask it = new InvokeTask(rpcRequest,ctx);
         NettyServer.submit(it);
     }
 
 
     @Override
     public void handlerAdded(ChannelHandlerContext ctx) throws Exception{
         this.context = ctx;     
     }
     
 }

给出 InvokeTask 的对应实现。

public class InvokeTask implements Runnable{
 
     private RpcRequest invocation;
     private ChannelHandlerContext ctx;
 
     public InvokeTask(RpcRequest invocation,ChannelHandlerContext ctx) {
         super();
         this.invocation = invocation;
         this.ctx = ctx;
     }
 
 
     @Override
     public void run() {
         
         // 从注册中心根据接口，找接口的实现类
         String interFaceName = invocation.getInterfaceName();
         Class impClass = null;
         try {
             impClass = Class.forName(invocation.getImpl());
         } catch (ClassNotFoundException e) {
             e.printStackTrace();
         }
 
         Method method;
         Object result = null;
         try {
             method = impClass.getMethod(invocation.getMethodName(),invocation.getParamTypes());
             //这块考虑实现类，是不是应该在 spring 里面拿
             result = method.invoke(impClass.newInstance(),invocation.getParams());
         } catch (Exception e) {
             e.printStackTrace();
         }
         RpcResponse rpcResponse = new RpcResponse();
         rpcResponse.setResponseId(invocation.getRequestId());
         rpcResponse.setData(result);
         ctx.writeAndFlush(rpcResponse).addListener(new ChannelFutureListener() {
             public void operationComplete(ChannelFuture channelFuture) throws Exception {
                 System.out.println("RPC Server Send message-id respone:" + invocation.getRequestId());
             }
         });
 
     }
 
 }

再来看客户端，客户端有两种实现，一种是不能复用 handler（可以立即为 connection）的模式，这种模式并发不太高，另一种是能够复用 handler 的 handlerPool 模式。

不能复用的模式。

public class NettyClient {
     private static NettyClient INSTANCE = new NettyClient();
 
     private final static int parallel = Runtime.getRuntime().availableProcessors() * 2;
 
     private NettyClient(){};
 
     public static NettyClient getInstance(){
         return INSTANCE;
     }
 
     private SerializeType serializeType = SerializeType.queryByType(Configuration.getInstance().getSerialize());
 
     public void start(String host,Integer port){
 
         Bootstrap bootstrap = new Bootstrap();
         EventLoopGroup group = new NioEventLoopGroup(parallel);
 
         try{
             bootstrap.group(group)
                     .channel(NioSocketChannel.class)
                     .handler(new ChannelInitializer<SocketChannel>(){
 
                         @Override
                         protected void initChannel(SocketChannel arg0) throws Exception {
                             ChannelPipeline pipeline = arg0.pipeline();
                             //ObjectDecoder的基类半包解码器LengthFieldBasedFrameDecoder的报文格式保持兼容。因为底层的父类LengthFieldBasedFrameDecoder
                             //的初始化参数即为super(maxObjectSize, 0, 4, 0, 4);
 //                          pipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, 4, 0, 4));
                             //利用LengthFieldPrepender回填补充ObjectDecoder消息报文头
 //                          pipeline.addLast(new LengthFieldPrepender(4));
 //                          pipeline.addLast(new ObjectEncoder());
                             //考虑到并发性能，采用weakCachingConcurrentResolver缓存策略。一般情况使用:cacheDisabled即可
 //                          pipeline.addLast(new ObjectDecoder(Integer.MAX_VALUE, ClassResolvers.weakCachingConcurrentResolver(this.getClass().getClassLoader())));
                             //注册Netty编码器
                             System.out.println("11111111:"+serializeType.getSerializeType());
                             pipeline.addLast(new NettyEncoderHandler(serializeType));
                             //注册Netty解码器
                             pipeline.addLast(new NettyDecoderHandler(RpcResponse.class, serializeType));
                             pipeline.addLast("handler", new NettyClientHandler());
 
                         }
 
                     });
             ChannelFuture future = bootstrap.connect(host,port).sync();
         }catch(Exception e){
             group.shutdownGracefully();
         }
 
 
     }
 }

在看可复用的模式，固定 handler 数量，目前框架中使用的是可复用模式，上面的不可复用的没用上，为了给大家理解，没有删除。

public class NettyChannelPoolFactory {
 
     //初始化Netty Channel阻塞队列的长度,该值为可配置信息
     private static final int channelConnectSize = 10;
     
     //Key为服务提供者地址,value为Netty Channel阻塞队列
     private static final Map<URL, ArrayBlockingQueue<Channel>> channelPoolMap = new ConcurrentHashMap<>();
     
     private static NettyChannelPoolFactory INSTANCE = new NettyChannelPoolFactory();
     
     private NettyChannelPoolFactory(){};
     
     public static NettyChannelPoolFactory getInstance(){
         return INSTANCE;
     }
 
     private List<ServiceProvider> serviceMetaDataList = new ArrayList<>();
     
     //根据配置文件里面需要调用的接口信息来初始化 channel
     public void initNettyChannelPoolFactory(Map<String, List<ServiceProvider>> providerMap){
 
         //将服务提供者信息存入serviceMetaDataList列表
         Collection<List<ServiceProvider>> collectionServiceMetaDataList = providerMap.values();
         for (List<ServiceProvider> serviceMetaDataModels : collectionServiceMetaDataList) {
             if (CollectionUtils.isEmpty(serviceMetaDataModels)) {
                 continue;
             }
             serviceMetaDataList.addAll(serviceMetaDataModels);
         }
 
         //获取服务提供者地址列表
         Set<URL> set = new HashSet<>();
         for (ServiceProvider serviceMetaData : serviceMetaDataList) {
             String serviceIp = serviceMetaData.getIp();
             int servicePort = serviceMetaData.getPort();
             URL url = new URL(serviceIp,servicePort);
             set.add(url);
         }
         
         for(URL url:set){
             //为每个 ip端口 建立多个 channel，并且放入阻塞队列中
             int channelSize = 0;
             while(channelSize < channelConnectSize){
                 Channel channel = null;
                 while(channel == null){
                     channel = registerChannel(url);
                 }
                 
                 channelSize ++;
                 
                 ArrayBlockingQueue<Channel> queue = channelPoolMap.get(url);
                 if(queue == null){
                     queue = new ArrayBlockingQueue<Channel>(channelConnectSize);
                     channelPoolMap.put(url, queue);
                 }
                 queue.offer(channel);
                 
             }
         }
         
     }
 
     public Channel registerChannel(URL url) {
         final SerializeType serializeType = SerializeType.queryByType(Configuration.getInstance().getSerialize());
         Bootstrap bootstrap = new Bootstrap();
         EventLoopGroup group = new NioEventLoopGroup(10);
         
         try{
             bootstrap.group(group)
                 .channel(NioSocketChannel.class)
                 .handler(new ChannelInitializer<SocketChannel>(){
 
                 @Override
                 protected void initChannel(SocketChannel arg0) throws Exception {
                     ChannelPipeline pipeline = arg0.pipeline();
                     //ObjectDecoder的基类半包解码器LengthFieldBasedFrameDecoder的报文格式保持兼容。因为底层的父类LengthFieldBasedFrameDecoder
                     //的初始化参数即为super(maxObjectSize, 0, 4, 0, 4);
 //                  pipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, 4, 0, 4));
                     //利用LengthFieldPrepender回填补充ObjectDecoder消息报文头
 //                  pipeline.addLast(new LengthFieldPrepender(4));
 //                  pipeline.addLast(new ObjectEncoder());
                     //考虑到并发性能，采用weakCachingConcurrentResolver缓存策略。一般情况使用:cacheDisabled即可
 //                  pipeline.addLast(new ObjectDecoder(Integer.MAX_VALUE, ClassResolvers.weakCachingConcurrentResolver(this.getClass().getClassLoader())));
                     pipeline.addLast(new NettyEncoderHandler(serializeType));
                     //注册Netty解码器
                     pipeline.addLast(new NettyDecoderHandler(RpcResponse.class, serializeType));
                     pipeline.addLast("handler", new NettyClientHandler());
                     
                 }
                 
             });
             ChannelFuture future = bootstrap.connect(url.getHost(),url.getPort()).sync();
             Channel channel = future.channel();
             //等待Netty服务端链路建立通知信号
             final CountDownLatch connectedLatch = new CountDownLatch(1);
 
             final List<Boolean> isSuccess = new ArrayList<>(1);
             future.addListener(new ChannelFutureListener(){
 
                 @Override
                 public void operationComplete(ChannelFuture future)
                         throws Exception {
                     if(future.isSuccess()){
                         isSuccess.add(true);
                     }else{
                         isSuccess.add(false);
                     }
                     connectedLatch.countDown();
                 }
                 
             });
             connectedLatch.await();
             if(isSuccess.get(0)){
                 return channel;
             }
         }catch(Exception e){
             group.shutdownGracefully();
             e.printStackTrace();
         }
         return null;
     }
     //根据 url 获取阻塞队列
     public ArrayBlockingQueue<Channel> acqiure(URL url){
         System.out.println(channelPoolMap.toString());
         return channelPoolMap.get(url);
     }
     
     //channel 使用完毕后进行回收
     public void release(ArrayBlockingQueue<Channel> queue, Channel channel, URL url){
         if(queue == null){
             return;
         }
         //需要检查 channel 是否可用，如果不可用，重新注册一个放入阻塞队列中
         if(channel == null || !channel.isActive() || !channel.isOpen()|| !channel.isWritable()){
             if (channel != null) {
                 channel.deregister().syncUninterruptibly().awaitUninterruptibly();
                 channel.closeFuture().syncUninterruptibly().awaitUninterruptibly();
             }
             Channel c = null;
             while(c == null){
                 c = registerChannel(url);
             }
             queue.offer(c);
             return;
         }
         queue.offer(channel);
     }
 
 }

给出对应的 handler 实现，在 channelread0 里面读取 server 端返回的信息，因为 netty 是异步的，所以需要 MessageCallBack 来实现我们的同步调用。

public class NettyClientHandler extends SimpleChannelInboundHandler<RpcResponse> {

     private ChannelHandlerContext context;
 
     @Override
     public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
             throws Exception {
         cause.printStackTrace();
         ctx.close();
     }
 
     @Override
     public void channelInactive(ChannelHandlerContext ctx) throws Exception {
         System.out.println("停止时间是："+new Date());
         System.out.println("HeartBeatClientHandler channelInactive");
     }
 
     @Override
     public void channelActive(ChannelHandlerContext ctx) throws Exception {
         this.context = ctx;
         System.out.println("激活时间是："+ctx.channel().id());
     }
 
 
     @Override
     protected void channelRead0(ChannelHandlerContext channelHandlerContext, RpcResponse rpcResponse) throws Exception {
         // String res = (String)msg;
         //RpcResponse rpcResponse = (RpcResponse)msg;
         String responseId = rpcResponse.getResponseId();
         MessageCallBack callBack = ResponseHolder.getInstance().mapCallBack.get(responseId);
         if(callBack != null){
             ResponseHolder.getInstance().mapCallBack.remove(responseId);
             callBack.over(rpcResponse);
         }
     }
 }

MessageCallBack 的实现。

public class MessageCallBack {
 
     private RpcRequest rpcRequest;
     
     private RpcResponse rpcResponse;
     
     private Lock lock = new ReentrantLock();
     
     private Condition finish = lock.newCondition();
     
     public MessageCallBack(RpcRequest request) {
         this.rpcRequest = request;
     }
 
     public Object start() throws InterruptedException {
         try {
             lock.lock();
             //设定一下超时时间，rpc服务器太久没有相应的话，就默认返回空吧。
             finish.await(10*1000, TimeUnit.MILLISECONDS);
             if (this.rpcResponse != null) {
                 return this.rpcResponse.getData();
             } else {
                 return null;
             }
         } finally {
             lock.unlock();
         }
     }
 
     public void over(RpcResponse reponse) {
         try {
             lock.lock();
             this.rpcResponse = reponse;
             finish.signal();
         } finally {
             lock.unlock();
         }
     }
 
 }

既然是可插拔式框架，那么底层协议一定要是可选择的，所以我们定义一个顶层接口来支持我们选择协议。
start 方法是启动服务端，send 方法是客户端发送数据。

public interface Procotol {
 
     void start(URL url);
     Object send(URL url, RpcRequest invocation);
 }

对应的三个协议的接口实现。
Netty 的实现

public class DubboProcotol implements Procotol {
     @Override
     public void start(URL url) {
         NettyServer nettyServer = NettyServer.getInstance();
         nettyServer.start(url.getHost(),url.getPort());
     }
 
     @Override
     public Object send(URL url, RpcRequest invocation) {
         ArrayBlockingQueue<Channel> queue = NettyChannelPoolFactory.getInstance().acqiure(url);
         Channel channel = null;
         try {
             channel = queue.poll(invocation.getTimeout(), TimeUnit.MILLISECONDS);
             if(channel == null || !channel.isActive() || !channel.isOpen()|| !channel.isWritable()){
                 channel = queue.poll(invocation.getTimeout(), TimeUnit.MILLISECONDS);
                 if(channel == null){
                     channel = NettyChannelPoolFactory.getInstance().registerChannel(url);
                 }
             }
             //将本次调用的信息写入Netty通道,发起异步调用
             ChannelFuture channelFuture = channel.writeAndFlush(invocation);
             channelFuture.syncUninterruptibly();
             MessageCallBack callback = new MessageCallBack(invocation);
             ResponseHolder.getInstance().mapCallBack.put(invocation.getRequestId(), callback);
             try {
                 return callback.start();
             } catch (InterruptedException e) {
                 e.printStackTrace();
             }
             return null;
         } catch (InterruptedException e1) {
             e1.printStackTrace();
         }finally{
             System.out.println("release:"+channel.id());
             NettyChannelPoolFactory.getInstance().release(queue, channel, url);
         }
         return null;
     }
 }

http 的实现

public class HttpProcotol implements Procotol {
     @Override
     public void start(URL url) {
         HttpServer httpServer = HttpServer.getInstance();
         httpServer.start(url.getHost(),url.getPort());
     }
 
     @Override
     public Object send(URL url, RpcRequest invocation) {
         HttpClient httpClient = HttpClient.getInstance();
         return httpClient.post(url.getHost(),url.getPort(),invocation);
     }
 }

Socket 的实现

public class SocketProcotol implements Procotol {
     @Override
     public void start(URL url) {
         SocketServer socketServer = SocketServer.getInstance();
         socketServer.publiser(url.getPort());
     }
 
     @Override
     public Object send(URL url, RpcRequest invocation) {
         SocketClient socketClient = SocketClient.getInstance();
         return socketClient.sendRequest(url.getHost(),url.getPort(),invocation);
     }
 }

这样一个可选择协议的模型就实现了，我们可已通过这个模块选择协议，并且与服务端通信。

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