Spring Webflux HttpHandler源码整理

HttpHandler的构造

自动启动配置类：HttpHandlerAutoConfiguration

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@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;
}

ApplicationContext.applicationContext

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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
...

WebHttpHandlerBuilder#build构建HttpHandler

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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);
}

实例化FilteringWebHandler

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

实例化DefaultWebFilterChain

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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;
 }

initChain代码片段

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 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

HttpWebHandlerAdapter#handle执行

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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));
}

ExceptionHandlingWebHandler#handle(exchange)执行

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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;
}

FilteringWebHandler#handle

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

DefaultWebFilterChain#filter执行

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 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]");
 }

DispatcherHandler#handle执行