Spring Webflux HttpHandler源码整理

HttpHandler的构造

1. 自动启动配置类：HttpHandlerAutoConfiguration

   @Bean
   public HttpHandler httpHandler(ObjectProvider<WebFluxProperties> propsProvider) {HttpHandler httpHandler = WebHttpHandlerBuilder.applicationContext(this.applicationContext).build();WebFluxProperties properties = propsProvider.getIfAvailable();if (properties != null && StringUtils.hasText(properties.getBasePath())) {Map<String, HttpHandler> handlersMap = Collections.singletonMap(properties.getBasePath(), httpHandler);return new ContextPathCompositeHandler(handlersMap);}return httpHandler;
   }
   

2. ApplicationContext.applicationContext

   获取spring容器中的WebHandler并保存到WebHttpHandlerBuilder中 (这里传入的WebHandler为DispatcherHandler实例)
   获取spring容器中的WebFilter并保存到WebHttpHandlerBuilder中
   获取spring容器中的WebExceptionHandler并保存到WebHttpHandlerBuilder中
   获取spring容器中的HttpHandlerDecoratorFactory并保存到WebHttpHandlerBuilder中
   获取spring容器中WebSessionManager并保存到WebHttpHandlerBuilder中
   ...
   

3. WebHttpHandlerBuilder#build构建HttpHandler

   public HttpHandler build() {WebHandler decorated = new FilteringWebHandler(this.webHandler, this.filters);decorated = new ExceptionHandlingWebHandler(decorated,  this.exceptionHandlers);HttpWebHandlerAdapter adapted = new HttpWebHandlerAdapter(decorated);adapted.setSessionManager(this.sessionManager);adapted.setCodecConfigurer(this.codecConfigurer);adapted.setLocaleContextResolver(this.localeContextResolver);adapted.setForwardedHeaderTransformer(this.forwardedHeaderTransformer);adapted.setApplicationContext(this.applicationContext);adapted.afterPropertiesSet();return (this.httpHandlerDecorator != null ? this.httpHandlerDecorator.apply(adapted) : adapted);
   }
   

4. 实例化FilteringWebHandler

   public FilteringWebHandler(WebHandler handler, List<WebFilter> filters) {this.delegate = handler;this.chain = new DefaultWebFilterChain(handler, filters);
   }
   

5. 实例化DefaultWebFilterChain

   public DefaultWebFilterChain(WebHandler handler, List<WebFilter> filters) {this.allFilters = Collections.unmodifiableList(filters);this.handler = handler;DefaultWebFilterChain chain = initChain(filters, handler);this.currentFilter = chain.currentFilter;this.chain = chain.chain;}
   

6. initChain代码片段

    private static DefaultWebFilterChain initChain(List<WebFilter> filters, WebHandler handler) {DefaultWebFilterChain chain = new DefaultWebFilterChain(filters, handler, null, null);ListIterator<? extends WebFilter> iterator = filters.listIterator(filters.size());while (iterator.hasPrevious()) {chain = new DefaultWebFilterChain(filters, handler, iterator.previous(), chain);}return chain;}
   

HttpHandler的执行

1. HttpWebHandlerAdapter#handle执行

   public Mono<Void> handle(ServerHttpRequest request, ServerHttpResponse response) {ServerWebExchange exchange = createExchange(request, response);return getDelegate().handle(exchange).doOnSuccess(aVoid -> logResponse(exchange)).onErrorResume(ex -> handleUnresolvedError(exchange, ex)).then(Mono.defer(response::setComplete));
   }
   

2. ExceptionHandlingWebHandler#handle(exchange)执行

   public Mono<Void> handle(ServerWebExchange exchange) {Mono<Void> completion;try {completion = super.handle(exchange);}catch (Throwable ex) {completion = Mono.error(ex);}for (WebExceptionHandler handler : this.exceptionHandlers) {completion = completion.onErrorResume(ex -> handler.handle(exchange, ex));}return completion;
   }
   

3. FilteringWebHandler#handle

   public Mono<Void> handle(ServerWebExchange exchange) {return this.chain.filter(exchange);
   }
   

4. DefaultWebFilterChain#filter执行

    public Mono<Void> filter(ServerWebExchange exchange) {return Mono.defer(() ->this.currentFilter != null && this.chain != null ?invokeFilter(this.currentFilter, this.chain, exchange) :this.handler.handle(exchange));}private Mono<Void> invokeFilter(WebFilter current, DefaultWebFilterChain chain, ServerWebExchange exchange) {String currentName = current.getClass().getName();return current.filter(exchange, chain).checkpoint(currentName + " [DefaultWebFilterChain]");}
   

5. DispatcherHandler#handle执行