你的响应阻塞了没有？--Spring-WebFlux源码分析

/**
 * Central dispatcher for HTTP request handlers/controllers. Dispatches to
 * registered handlers for processing a request, providing convenient mapping
 * facilities.
 *
 * <p>{@code DispatcherHandler} discovers the delegate components it needs from
 * Spring configuration. It detects the following in the application context:
 * <ul>
 * <li>{@link HandlerMapping} -- map requests to handler objects
 * <li>{@link HandlerAdapter} -- for using any handler interface
 * <li>{@link HandlerResultHandler} -- process handler return values
 * </ul>
 *
 * <p>{@code DispatcherHandler} is also designed to be a Spring bean itself and
 * implements {@link ApplicationContextAware} for access to the context it runs
 * in. If {@code DispatcherHandler} is declared with the bean name "webHandler"
 * it is discovered by {@link WebHttpHandlerBuilder#applicationContext} which
 * creates a processing chain together with {@code WebFilter},
 * {@code WebExceptionHandler} and others.
 *
 * <p>A {@code DispatcherHandler} bean declaration is included in
 * {@link org.springframework.web.reactive.config.EnableWebFlux @EnableWebFlux}
 * configuration.
 *
 * @author Rossen Stoyanchev
 * @author Sebastien Deleuze
 * @author Juergen Hoeller
 * @since 5.0
 * @see WebHttpHandlerBuilder#applicationContext(ApplicationContext)
 */

    protected void initStrategies(ApplicationContext context) {
        Map<String, HandlerMapping> mappingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(
                context, HandlerMapping.class, true, false);  //1 

        ArrayList<HandlerMapping> mappings = new ArrayList<>(mappingBeans.values());
        AnnotationAwareOrderComparator.sort(mappings);
        this.handlerMappings = Collections.unmodifiableList(mappings);

        Map<String, HandlerAdapter> adapterBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(
                context, HandlerAdapter.class, true, false);  //2 

        this.handlerAdapters = new ArrayList<>(adapterBeans.values());
        AnnotationAwareOrderComparator.sort(this.handlerAdapters);

        Map<String, HandlerResultHandler> beans = BeanFactoryUtils.beansOfTypeIncludingAncestors(
                context, HandlerResultHandler.class, true, false); //3

        this.resultHandlers = new ArrayList<>(beans.values());
        AnnotationAwareOrderComparator.sort(this.resultHandlers);
    }

    public Mono<Void> handle(ServerWebExchange exchange) {
        if (this.handlerMappings == null) {
            return createNotFoundError();
        }
        return Flux.fromIterable(this.handlerMappings)
                .concatMap(mapping -> mapping.getHandler(exchange))//1
                .next()
                .switchIfEmpty(createNotFoundError())//2
                .flatMap(handler -> invokeHandler(exchange, handler))//3
                .flatMap(result -> handleResult(exchange, result));//4
    }

    private Mono<HandlerResult> invokeHandler(ServerWebExchange exchange, Object handler) {
        if (this.handlerAdapters != null) {
            for (HandlerAdapter handlerAdapter : this.handlerAdapters) {
                if (handlerAdapter.supports(handler)) {
                    return handlerAdapter.handle(exchange, handler);
                }
            }
        }
        return Mono.error(new IllegalStateException("No HandlerAdapter: " + handler));
    }

    private Mono<Void> handleResult(ServerWebExchange exchange, HandlerResult result) {
        return getResultHandler(result).handleResult(exchange, result)
                .onErrorResume(ex -> result.applyExceptionHandler(ex).flatMap(exceptionResult ->
                        getResultHandler(exceptionResult).handleResult(exchange, exceptionResult)));
    }

    private HandlerResultHandler getResultHandler(HandlerResult handlerResult) {
        if (this.resultHandlers != null) {
            for (HandlerResultHandler resultHandler : this.resultHandlers) {
                if (resultHandler.supports(handlerResult)) {
                    return resultHandler;
                }
            }
        }
        throw new IllegalStateException("No HandlerResultHandler for " + handlerResult.getReturnValue());
    }

    @Override
    public Mono<Void> apply(HttpServerRequest reactorRequest, HttpServerResponse reactorResponse) {
        NettyDataBufferFactory bufferFactory = new NettyDataBufferFactory(reactorResponse.alloc());
        try {
            ReactorServerHttpRequest request = new ReactorServerHttpRequest(reactorRequest, bufferFactory);
            ServerHttpResponse response = new ReactorServerHttpResponse(reactorResponse, bufferFactory);

            if (request.getMethod() == HttpMethod.HEAD) {
                response = new HttpHeadResponseDecorator(response);
            }

            return this.httpHandler.handle(request, response)
                    .doOnError(ex -> logger.trace(request.getLogPrefix() + "Failed to complete: " + ex.getMessage()))
                    .doOnSuccess(aVoid -> logger.trace(request.getLogPrefix() + "Handling completed"));
        }
        catch (URISyntaxException ex) {
            if (logger.isDebugEnabled()) {
                logger.debug("Failed to get request URI: " + ex.getMessage());
            }
            reactorResponse.status(HttpResponseStatus.BAD_REQUEST);
            return Mono.empty();
        }
    }

**
 * Lowest level contract for reactive HTTP request handling that serves as a
 * common denominator across different runtimes.
 *
 * <p>Higher-level, but still generic, building blocks for applications such as
 * {@code WebFilter}, {@code WebSession}, {@code ServerWebExchange}, and others
 * are available in the {@code org.springframework.web.server} package.
 *
 * <p>Application level programming models such as annotated controllers and
 * functional handlers are available in the {@code spring-webflux} module.
 *
 * <p>Typically an {@link HttpHandler} represents an entire application with
 * higher-level programming models bridged via
 * {@link org.springframework.web.server.adapter.WebHttpHandlerBuilder}.
 * Multiple applications at unique context paths can be plugged in with the
 * help of the {@link ContextPathCompositeHandler}.
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @since 5.0
 * @see ContextPathCompositeHandler
 */

/**
 * {@code HttpHandler} delegating requests to one of several {@code HttpHandler}‘s
 * based on simple, prefix-based mappings.
 *
 * <p>This is intended as a coarse-grained mechanism for delegating requests to
 * one of several applications -- each represented by an {@code HttpHandler}, with
 * the application "context path" (the prefix-based mapping) exposed via
 * {@link ServerHttpRequest#getPath()}.
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 */
    @Override
    public Mono<Void> handle(ServerHttpRequest request, ServerHttpResponse response) {
        // Remove underlying context path first (e.g. Servlet container)
        String path = request.getPath().pathWithinApplication().value();
        return this.handlerMap.entrySet().stream()
                .filter(entry -> path.startsWith(entry.getKey()))
                .findFirst()
                .map(entry -> {
                    String contextPath = request.getPath().contextPath().value() + entry.getKey();
                    ServerHttpRequest newRequest = request.mutate().contextPath(contextPath).build();
                    return entry.getValue().handle(newRequest, response);
                })
                .orElseGet(() -> {
                    response.setStatusCode(HttpStatus.NOT_FOUND);
                    return response.setComplete();
                });
    }

@Override
    public void service(ServletRequest request, ServletResponse response) throws ServletException, IOException {
        // Check for existing error attribute first
        if (DispatcherType.ASYNC.equals(request.getDispatcherType())) {
            Throwable ex = (Throwable) request.getAttribute(WRITE_ERROR_ATTRIBUTE_NAME);
            throw new ServletException("Failed to create response content", ex);
        }

        // Start async before Read/WriteListener registration
        AsyncContext asyncContext = request.startAsync();
        asyncContext.setTimeout(-1);

        ServletServerHttpRequest httpRequest;
        try {
            httpRequest = createRequest(((HttpServletRequest) request), asyncContext);//1
        }
        catch (URISyntaxException ex) {
            if (logger.isDebugEnabled()) {
                logger.debug("Failed to get request  URL: " + ex.getMessage());
            }
            ((HttpServletResponse) response).setStatus(400);
            asyncContext.complete();
            return;
        }

        ServerHttpResponse httpResponse = createResponse(((HttpServletResponse) response), asyncContext, httpRequest);//2
        if (httpRequest.getMethod() == HttpMethod.HEAD) {
            httpResponse = new HttpHeadResponseDecorator(httpResponse);
        }

        AtomicBoolean isCompleted = new AtomicBoolean();
        HandlerResultAsyncListener listener = new HandlerResultAsyncListener(isCompleted, httpRequest);
        asyncContext.addListener(listener);

        HandlerResultSubscriber subscriber = new HandlerResultSubscriber(asyncContext, isCompleted, httpRequest);
        this.httpHandler.handle(httpRequest, httpResponse).subscribe(subscriber);//3
    }

@Override
    public void onStartup(ServletContext servletContext) throws ServletException {
        String servletName = getServletName();
        Assert.hasLength(servletName, "getServletName() must not return null or empty");

        ApplicationContext applicationContext = createApplicationContext();
        Assert.notNull(applicationContext, "createApplicationContext() must not return null");

        refreshApplicationContext(applicationContext);
        registerCloseListener(servletContext, applicationContext);

        HttpHandler httpHandler = WebHttpHandlerBuilder.applicationContext(applicationContext).build();
        ServletHttpHandlerAdapter servlet = new ServletHttpHandlerAdapter(httpHandler);

        ServletRegistration.Dynamic registration = servletContext.addServlet(servletName, servlet);
        if (registration == null) {
            throw new IllegalStateException("Failed to register servlet with name ‘" + servletName + "‘. " +
                    "Check if there is another servlet registered under the same name.");
        }

        registration.setLoadOnStartup(1);
        registration.addMapping(getServletMapping());
        registration.setAsyncSupported(true);
    }