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 createChannelInitializer() {
2. final RequestDispatcher dispatcher =createRequestDispatcher();
3. if (sslContext == null) {
4. return newChannelInitializer() {
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() {
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 dispatcher) {
5. this.dispatcher = dispatcher;
6. }
7.
8. @Override
9. protected voidchannelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {
10. if (msg instanceof NettyHttpRequest) {
11.
12. NettyHttpRequest request =(NettyHttpRequest) msg;
13.
14. try {
15. if(EventBus.isEnable(RestServerReceiveEvent.class)) {
16. EventBus.post(newRestServerReceiveEvent(request));
17. }
18.
19. if(request.getUri().getPath().endsWith("/favicon.ico")) {
20. HttpResponse response = newDefaultHttpResponse(HTTP_1_1, NOT_FOUND);
21. ctx.writeAndFlush(response);
22.
23. if(EventBus.isEnable(RestServerSendEvent.class)) {
24. EventBus.post(newRestServerSendEvent(request, null, null));
25. }
26. return;
27. }
28.
29. if(request.is100ContinueExpected()) {
30. send100Continue(ctx);
31. }
32.
33. NettyHttpResponse response =request.getResponse();
34. Exception exception = null;
35. try {
36. // 获取远程ip 兼容nignx转发和vip等
37. HttpHeaders httpHeaders =request.getHttpHeaders();
38. String remoteip =httpHeaders.getHeaderString("X-Forwarded-For");
39. if (remoteip == null) {
40. remoteip =httpHeaders.getHeaderString("X-Real-IP");
41. }
42. if (remoteip != null) {
43. RpcInternalContext.getContext().setRemoteAddress(remoteip,0);
44. } else { // request取不到就从channel里取
45. RpcInternalContext.getContext().setRemoteAddress(
46. (InetSocketAddress)ctx.channel().remoteAddress());
47. }
48. // 设置本地地址
49. RpcInternalContext.getContext().setLocalAddress((InetSocketAddress)ctx.channel().localAddress());
50.
51. dispatcher.service(ctx, request, response,true);
52. } catch (Failure e1) {
53. response.reset();
54. response.setStatus(e1.getErrorCode());
55. exception = e1;
56. } catch (Exception ex) {
57. response.reset();
58. response.setStatus(500);
59. logger.error("Unexpected",ex); // todo 异常带给用户?
60. exception = ex;
61. } finally {
62. if(EventBus.isEnable(RestServerSendEvent.class)) {
63. EventBus.post(newRestServerSendEvent(request, response, exception));
64. }
65. }
66.
67. if(!request.getAsyncContext().isSuspended()) {
68. response.finish();
69. ctx.flush();
70. }
71. } finally {
72. if(EventBus.isEnable(ServerEndHandleEvent.class)) {
73. EventBus.post(newServerEndHandleEvent());
74. }
75. RpcInvokeContext.removeContext();
76. RpcInternalContext.removeAllContext();
77. }
78. }
79. }
80.
81. private voidsend100Continue(ChannelHandlerContext ctx) {
82. HttpResponse response = new DefaultHttpResponse(HTTP_1_1,CONTINUE);
83. ctx.writeAndFlush(response);
84. }
85.
86. @Override
87. public voidexceptionCaught(ChannelHandlerContext ctx, Throwable e)
88. throws Exception {
89. ……略
90. }
91. }
当Netty4服务器接收到客户端Http请求，按照顺序依次调用其ChannelPipeline中配置的上行处理器处理Http请求。 此处，上行处理器的执行顺序为：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。
当请求到达最后一个处理SofaRestRequestHandler时，调用其channelRead0方法，处理Http请求：
1. 经过RestEasyHttpRequestDecoder解码器处理以后，Http请求已经被转换为JBoss RestEasy的NettyHttpRequest实例request；
2. 从NettyHttpRequest中获取NettyHttpResponse实例response；
3. 获取远程IP地址、兼容Nignx转发和VIP等、设置本地地址等；
4. 调用org.jboss.resteasy.plugins.server.netty.RequestDispatcher的service方法，分发Http请求；
5. RequestDispatcher的service方法中，调用com.alipay.sofa.rpc.server.rest.SofaSynchronousDispatcher的invoke方法：
1. public void invoke(HttpRequest request,HttpResponse response) {
2. try{
3. pushContextObjects(request, response);
4. if (!preprocess(request, response))return;
5. ResourceInvoker invoker = null;
6. try {
7. invoker = getInvoker(request);
8. } catch (Exception exception) {
9. //logger.error("getInvoker()failed mapping exception", exception);
10. writeException(request, response,exception);
11. return;
12. }
13. invoke(request, response, invoker);
14. }
15. finally {
16. clearContextData();
17. }
18. }
调用getInvoker方法：
1. public ResourceInvokergetInvoker(HttpRequest request) throwsFailure {
2. logger.debug("PathInfo: " +request.getUri().getPath());
3. if (!request.isInitial())
4. {
5. throw newInternalServerErrorException(……略);
6. }
7. ResourceInvoker invoker =registry.getResourceInvoker(request);
8. if (invoker == null)
9. {
10. throw new NotFoundException(……略);
11. }
12. return invoker;
13. }
调用com.alipay.sofa.rpc.server.rest.SofaResourceMethodRegistry类getResourceInvoker方法，解析请求中的路径, 然后匹配到相应的invoker（此处为com.alipay.sofa.rpc.server.rest.SofaResourceMethodInvoker实例）来执行客户端请求。例如：该Http请求路径为：/webapi/rest/person/sayName/Mike,匹配到相应的invoker为SofaResourceMethodInvoker的一个实例；
获取Http请求对应的invoker以后，调用SofaSynchronousDispatcher的invoke(HttpRequestrequest, HttpResponse response, ResourceInvoker invoker)方法，处理请求：
1. public void invoke(HttpRequest request,HttpResponse response, ResourceInvoker invoker)
2. {
3. Response jaxrsResponse = null;
4. try {
5. jaxrsResponse = invoker.invoke(request,response);
6. if(request.getAsyncContext().isSuspended()) {
7. ……略 request.getAsyncContext().getAsyncResponse().initialRequestThreadFinished();
8. jaxrsResponse = null; // we'rehanding response asynchronously
9. }
10. } catch (Exception e) {
11. //logger.error("invoke() failedmapping exception", e);
12. writeException(request, response, e);
13. return;
14. }
15.
16. if (jaxrsResponse != null)writeResponse(request, response, jaxrsResponse);
17. }
此时，调用SofaResourceMethodInvoker的invoke方法，处理请求：
1. public BuiltResponse invoke(HttpRequestrequest, HttpResponse response) {
2. Object target =resource.createResource(request, response, resourceMethodProviderFactory);
3. return invoke(request, response, target);
4. }
调用com.alipay.sofa.rpc.server.rest.SofaResourceFactory的createResource方法，获取响应Http请求的目标对象，此处为PersonServiceImpl的一个实例。
调用invoke方法:
1. public BuiltResponse invoke(HttpRequestrequest, HttpResponse response, Object target)
2. {
3. ……略
4. BuiltResponse rtn = invokeOnTarget(request,response, target);
5. return rtn;
6. }
调用invokeOnTarget方法：
1. protected BuiltResponseinvokeOnTarget(HttpRequest request, HttpResponse response, Object target) {
2. ……略
3.
4. Object rtn = null;
5. try
6. {
7. rtn = methodInjector.invoke(request, response,target);
8. }
9. catch (RuntimeException ex)
10. {
11. ……略
12. }
13. ……略
14. jaxrsResponse.addMethodAnnotations(getMethodAnnotations());
15. return jaxrsResponse;
16. }
调用org.jboss.resteasy.core.MethodInjectorImpl的invoke方法：
1. public Object invoke(HttpRequest request,HttpResponse httpResponse, Object resource) throws Failure,ApplicationException {
2. ……略
3. Object result = null;
4. try
5. {
6. result = invokedMethod.invoke(resource, args);
7. }
8. catch (IllegalAccessException e) {
9. ……略
10. }
11. catch (InvocationTargetException e) {
12. ……略
13. }
14. catch (IllegalArgumentException e) {
15. ……略
16. }
17. ……略
18. return result;
19. }
最后，通过Java反射机制，调用目标类上指定的方法，此处为PersonService的sayName方法。到此为止，请求处理完成，并返回处理结果。
再来看一下SofaRestRequestHandler的channelRead0方法：
1. public class SofaRestRequestHandlerextends SimpleChannelInboundHandler {
2.
3. @Override
4. protected void channelRead0(ChannelHandlerContextctx, Object msg) throws Exception {
5. if (msg instanceof NettyHttpRequest) {
6.
7. NettyHttpRequest request =(NettyHttpRequest) msg;
8.
9. try {
10. ……略
11. NettyHttpResponse response = request.getResponse();
12. Exception exception = null;
13. try {
14. // 获取远程ip 兼容nignx转发和vip等
15. ……略
16. // 设置本地地址
17. ……略
18. dispatcher.service(ctx, request, response,true);
19. } catch (Failure e1) {
20. ……略
21. } catch (Exception ex) {
22. ……略
23. } finally {
24. ……略 }
25.
26. if (!request.getAsyncContext().isSuspended()){
27. response.finish();
28. ctx.flush();
29. }
30. } finally {
31. ……略
32. }
33. }
34. }
35. }
当接收的处理结果response以后，调研NettyHttpResponse的finish方法，准备处理结果，并写入Channel。
1. publicvoid finish() throws IOException {
2. os.flush();
3. ChannelFuture future;
4. if (isCommitted()) {
5. // if committed this means the outputstream was used.
6. future =ctx.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT);
7. } else {
8. future =ctx.writeAndFlush(getEmptyHttpResponse());
9. }
10.
11. if(!isKeepAlive()) {
12. future.addListener(ChannelFutureListener.CLOSE);
13. }
14.
15. }
调用org.jboss.resteasy.plugins.server.netty.ChunkOutputStream的flush方法准备处理结果，并写入Channel。
1. public void flush() throws IOException {
2. int readable = buffer.readableBytes();
3. if (readable == 0) return;
4. if (!response.isCommitted()) response.prepareChunkStream();
5. ctx.writeAndFlush(new DefaultHttpContent(buffer.copy()));
6. buffer.clear();
7. super.flush();
8. }
最后，调用Netty4的DefaultChannelHandlerContext类writeAndFlush方法，把处理结果写入Channel。
在把处理结果通过网络返回给客户端以前，需要经过已经配置的下行处理器进行编码处理。下行处理器的执行顺序与配置顺序相反，所以按照逆序依次执行restful风格Http响应编码器RestEasyHttpResponseEncoder、自定义HTTP类型ChannelOutboundHandler、Http响应编码器、自定义非HTTP类型ChannelOutboundHandler，最终把已经编码好的处理结果的比特流，通过网络返回给客户端。