1. Spring WebFlux是什么?
Spring WebFlux是Spring Framework 5.0中引入的新的反应式Web框架。 与Spring MVC不同,它不需要Servlet API,完全异步和非阻塞, 并通过Reactor项目实现Reactive Streams规范。 并且可以在诸如Netty,Undertow和Servlet 3.1+容器的服务器上运行。Reactor 也是 Spring 5 中反应式编程的基础,它一个新的反应式编程库。
2. Reactor是什么?
Reactor offers non-blocking and backpressure-ready network runtimes including local TCP/HTTP/UDP client & servers based on the robust Netty framework.
Reactor提供了一个非阻塞的,高并发的基于健壮的Netty框架的网络运行API,包括本地tcp/http/udp 客户端和服务端。
重要的两个概念
Flux 和 Mono 是 Reactor 中的两个基本概念。Flux 表示的是包含 0 到 N 个元素的异步序列。在该序列中可以包含三种不同类型的消息通知:正常的包含元素的消息、序列结束的消息和序列出错的消息。当消息通知产生时,订阅者中对应的方法 onNext(), onComplete()和 onError()会被调用。Mono 表示的是包含 0 或者 1 个元素的异步序列。该序列中同样可以包含与 Flux 相同的三种类型的消息通知。Flux 和 Mono 之间可以进行转换。对一个 Flux 序列进行计数操作,得到的结果是一个 Mono
简单说Mono返回单个元素,Flux返回多个元素
3. spring webflux处理请求流程
核心控制器DispatcherHandler,等同于阻塞方式的DispatcherServlet//// Central dispatcher for HTTP request handlers/controllers. Dispatches to / registered handlers for processing a request, providing convenient mapping / facilities. / / {@codeDispatcherHandler} discovers the delegate components it needs from / /
{@codeDispatcherHandler} is also designed to be a Spring bean itself and /
implements {@linkApplicationContextAware} for access to the context it runs / in. If {@codeDispatcherHandler} is declared with the bean name "webHandler" / it is discovered by {@linkWebHttpHandlerBuilder/#applicationContext} which / creates a processing chain together with {@codeWebFilter}, / {@codeWebExceptionHandler} and others. / /A {@codeDispatcherHandler} bean declaration is included in / {@linkorg.springframework.web.reactive.config.EnableWebFlux @EnableWebFlux} / configuration. / /@authorRossen Stoyanchev /@authorSebastien Deleuze /@authorJuergen Hoeller /@since5.0 /@seeWebHttpHandlerBuilder/#applicationContext(ApplicationContext)/*/
3.1 初始化
获取HandlerMapping,HandlerAdapter,HandlerResultHandler的所有实例
protected voidinitStrategies(ApplicationContext context) { Map
其中,1.获取所有HandlerMapping实例
2.获取所有HandlerAdapter实例
3.获取所有HandlerResultHandler实例
3.2 流式处理请求public Mono
其中,第一步,从handlerMapping这个map中获取HandlerMapping
第二步,触发HandlerApter的handle方法private Mono
第三步,触发HandlerResultHandler 的handleResult方法
private Mono
4.HandlerMapping实现
5.HanlderAdapter的实现
6.HandlerResultHandler的实现
7.不同容器的实现
7.1 Reactor实现ReactorHttpHandlerAdapter
执行apply方法@Overridepublic Mono
其中,HttpHandler的定义
// / Lowest level contract forreactive HTTP request handling that serves as a/common denominator across different runtimes./ /
Higher-level, but still generic, building blocks forapplications such as/{@code WebFilter}, {@code WebSession}, {@code ServerWebExchange}, and others/ are available in the {@code org.springframework.web.server} package./ /
Application level programming models such as annotated controllers and/ functional handlers are available in the {@code spring-webflux} module./ / Typically an {@link HttpHandler} represents an entire application with/
具体的实现类为:ContextPathCompositeHandler
//// {@codeHttpHandler} delegating requests to one of several {@codeHttpHandler}'s /based on simple, prefix-based mappings. / /
This is intended as a coarse-grained mechanism for delegating requests to / one of several applications -- each represented by an {@codeHttpHandler}, with / the application "context path" (the prefix-based mapping) exposed via / {@linkServerHttpRequest/#getPath()}. / /@authorRossen Stoyanchev /@since5.0/*/@Overridepublic Mono
基于前缀的映射Handler
7.2 Jetty实现JettyHttpHandlerAdapter
继承自ServletHttpHandlerAdapter 实现了Servlet,执行service方法@Overridepublic void service(ServletRequest request, ServletResponse response) throwsServletException, IOException {//Check for existing error attribute first if(DispatcherType.ASYNC.equals(request.getDispatcherType())) { Throwable ex=(Throwable) request.getAttribute(WRITEERRORATTRIBUTE_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);//2if (httpRequest.getMethod() ==HttpMethod.HEAD) { httpResponse= newHttpHeadResponseDecorator(httpResponse); } AtomicBoolean isCompleted= newAtomicBoolean(); HandlerResultAsyncListener listener= newHandlerResultAsyncListener(isCompleted, httpRequest); asyncContext.addListener(listener); HandlerResultSubscriber subscriber= newHandlerResultSubscriber(asyncContext, isCompleted, httpRequest);this.httpHandler.handle(httpRequest, httpResponse).subscribe(subscriber);//3 }
其中,1.创建request
2.创建response
3.handler执行的结果进行subscribe
JettyHttpHandlerAdapter是ServletHttpHandlerAdapter 的扩展,重写了创建request 创建response方法
7.3 Tomcat实现TomcatHttpHandlerAdapter
TomcatHttpHandlerAdapter是ServletHttpHandlerAdapter 的扩展,重写了创建request 创建response方法
7.4 AbstractReactiveWebInitializer抽象类
继承自AbstractReactiveWebInitializer的类可以在servlet容器中安装一个Spring Reactive Web Application。@Overridepublic void onStartup(ServletContext servletContext) throwsServletException { 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); }
它通过将ServletHttpHandlerAdapter实例作为一个servlet安装到servler容器中。
8.总结
DispatcherHandler的流程是
1.通过 HandlerMapping(和DispathcherServlet中的HandlerMapping不同)获取到HandlerAdapter放到ServerWebExchange的属性中
2.获取到HandlerAdapter后触发handle方法,得到HandlerResult
3.通过HandlerResult,触发handleResult,针对不同的返回类找到不同的HandlerResultHandler如
视图渲染ViewResolutionResultHandler,ServerResponseResultHandler, ResponseBodyResultHandler, ResponseEntityResultHandler
不同容器有不同的实现,如Reactor,Jetty,Tomcat等。
参考文献:
【1】https://blog.csdn.net/qq_15144655/article/details/80708915
【2】https://www.ibm.com/developerworks/cn/java/j-cn-with-reactor-response-encode/index.html