SOFA RPC源码解析之Rest服务（4）-服务端响应

1 SOFA RPC源码解析

1.1 Rest服务

1.1.1  服务端响应

        在前文介绍SOFA RPC Rest服务发布过程的文章中，我们知道对于rest类型绑定，SOFA采用com.alipay.sofa.rpc.server.rest.SofaNettyJaxrsServer作为服务器。SofaNettyJaxrsServer采用Netty4作为网络通讯层。

        看一下SofaNettyJaxrsServer启动方法：

1.  public void start() {
2.          eventLoopGroup = newNioEventLoopGroup(ioWorkerCount, new NamedThreadFactory("SOFA-REST-IO-"+ port, daemon));
3.          eventExecutor = newNioEventLoopGroup(executorThreadCount, newNamedThreadFactory("SOFA-REST-BIZ-" + port, daemon));
4.          bootstrap.group(eventLoopGroup)
5.              .channel(NioServerSocketChannel.class)
6.              .childHandler(createChannelInitializer())
7.              .option(ChannelOption.SO_BACKLOG,backlog)
8.              .childOption(ChannelOption.SO_KEEPALIVE,keepAlive); // CHANGE:
9.   
10.         ……略
11.  
12.         bootstrap.bind(socketAddress).syncUninterruptibly();
13.     }

        在Server配置过程中，调用createChannelInitializer方法：

1.  privateChannelInitializer<SocketChannel> createChannelInitializer() {
2.          final RequestDispatcher dispatcher =createRequestDispatcher();
3.          if (sslContext == null) {
4.              return newChannelInitializer<SocketChannel>() {
5.                  @Override
6.                  public voidinitChannel(SocketChannel ch) throws Exception {
7.                      setupHandlers(ch, dispatcher, HTTP);
8.                  }
9.              };
10.         } else {
11.             final SSLEngine engine =sslContext.createSSLEngine();
12.             engine.setUseClientMode(false);
13.             return newChannelInitializer<SocketChannel>() {
14.                 @Override
15.                 public voidinitChannel(SocketChannel ch) throws Exception {
16.                     ch.pipeline().addFirst(newSslHandler(engine));
17.                     setupHandlers(ch, dispatcher, HTTPS);
18.                 }
19.             };
20.         }
21.     }

        无论是HTTP连接，或HTTPS连接，都会调用setupHandlers方法设置各种Netty4的ChannelInboundHandler和ChannelOutboundHandler处理器：

1.  private void setupHandlers(SocketChannelch, RequestDispatcher dispatcher,
2.                                 RestEasyHttpRequestDecoder.Protocolprotocol) {
3.          ChannelPipeline channelPipeline =ch.pipeline();
4.          channelPipeline.addLast(channelHandlers.toArray(newChannelHandler[channelHandlers.size()]));
5.          channelPipeline.addLast(newHttpRequestDecoder());
6.          channelPipeline.addLast(newHttpObjectAggregator(maxRequestSize));
7.          channelPipeline.addLast(newHttpResponseEncoder());
8.          channelPipeline.addLast(httpChannelHandlers.toArray(newChannelHandler[httpChannelHandlers.size()]));
9.          channelPipeline.addLast(newRestEasyHttpRequestDecoder(dispatcher.getDispatcher(), root, protocol));
10.         channelPipeline.addLast(newRestEasyHttpResponseEncoder());
11.         channelPipeline.addLast(eventExecutor,new SofaRestRequestHandler(dispatcher)); // CHANGE: 用sofa的处理类
12.     }

        由于SofaNettyJaxrsServer参考JBoss Resteasy的NettyJaxrsServer实现，除了根据SOFABoot框架自身需求增加一些自定义功能外，其它还是采用JBossResteasy的处理逻辑。所以，根据Resteasy需求，设置Netty4的上行处理器和下行处理器。

        其中，上行处理器主要包括自定义非HTTP类型ChannelInboundHandler、Http请求解码器HttpRequestDecoder、Http对象聚合器HttpObjectAggregator、自定义HTTP类型ChannelInboundHandler、restful风格Http请求解码器RestEasyHttpRequestDecoder、SOFA框架restful风格Http请求处理器SofaRestRequestHandler；

        下行处理器包括自定义非HTTP类型ChannelOutboundHandler、Http响应编码器、自定义HTTP类型ChannelOutboundHandler、restful风格Http响应编码器RestEasyHttpResponseEncoder；

        我们主要关注SOFA框架restful风格Http请求处理器，对于其他处理器，在这里不详细描述。

        从上述代码中，我们可以看出，SOFA框架的业务处理是在一个单独的线程组中执行，而非在Worker线程组（此处Boss和Worker采用同一个线程组），这样可以避免耗时较长的业务处理长时间占用IO线程，导致当大量并发请求到来时，无线程处理的问题。

        以下是SofaRestRequestHandler类的主要方法：

1.  public class SofaRestRequestHandlerextends SimpleChannelInboundHandler {
2.      protected final RequestDispatcherdispatcher;
3.      ……略
4.      publicSofaRestRequestHandler(RequestDispatcher disp