摘要：的這幾天看了看的請(qǐng)求處理流程，因?yàn)橹耙恢庇玫暮?，一開始對(duì)的處理流程有點(diǎn)懵逼，找不到入口，后來(lái)跟了代碼，在網(wǎng)上找了點(diǎn)資料，發(fā)現(xiàn)的入口在的方法該方法的作用就是把接收到的或者最終需要返回的，包裝轉(zhuǎn)換為和。

這幾天看了看spring-cloud-gateway的請(qǐng)求處理流程，因?yàn)橹耙恢庇玫膕pringboot1.x和spring4，一開始對(duì)spring-cloud-gateway的處理流程有點(diǎn)懵逼，找不到入口，后來(lái)跟了代碼，在網(wǎng)上找了點(diǎn)資料，發(fā)現(xiàn)spring-cloud-gateway的入口在ReactorHttpHandlerAdapter的apply方法

public class ReactorHttpHandlerAdapter implements BiFunction> {

    private static final Log logger = HttpLogging.forLogName(ReactorHttpHandlerAdapter.class);


    private final HttpHandler httpHandler;
    public ReactorHttpHandlerAdapter(HttpHandler httpHandler) {
        Assert.notNull(httpHandler, "HttpHandler must not be null");
        this.httpHandler = httpHandler;
    }
    @Override
    public Mono 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();
        }
    }

}

該方法的作用就是把接收到的HttpServerRequest或者最終需要返回的HttpServerResponse，包裝轉(zhuǎn)換為ReactorServerHttpRequest和ReactorServerHttpResponse。

當(dāng)然，這篇文章的主要內(nèi)容不是談?wù)搒pring-cloud-gateway了，因?yàn)橹耙恢庇玫膕pring4，所以對(duì)spring5當(dāng)中的反應(yīng)式編程范式和webflux不太了解，所以先寫個(gè)demo了解一下
第一步：引入相關(guān)pom,測(cè)試的相關(guān)pom根據(jù)自己的需要引入

    
        org.springframework.boot
        spring-boot-starter-parent
        2.1.4.RELEASE
         
    


    
        
            org.springframework.boot
            spring-boot-starter-webflux
        

        
            org.springframework.boot
            spring-boot-starter-test
            test
        
        
            io.projectreactor
            reactor-test
            test
        
    

第二步：創(chuàng)建一個(gè)HandlerFunction

public class TestFunction implements HandlerFunction {

    @Override
    public Mono handle(ServerRequest serverRequest) {
        return ServerResponse.ok().body(
                Mono.just(parse(serverRequest, "args1") + parse(serverRequest, "args2"))
                , Integer.class);
    }

    private int parse(final ServerRequest request, final String param) {
        return Integer.parseInt(request.queryParam(param).orElse("0"));
    }
}

第三步：注入一個(gè)RouterFunction

@Configuration
public class TestRouteFunction {

    @Bean
    public RouterFunction routerFunction() {
        return RouterFunctions.route(RequestPredicates.GET("/add"), new TestFunction());
    }
}

第四步：在webflux中，也可以使用之前的java注解的編程方式，我們也創(chuàng)建一個(gè)controller

@RestController
@RequestMapping("/api/test")
public class HelloController {

    @RequestMapping("/hello")
    public Mono hello() {
        return Mono.just("hello world");
    }
}

第五步：創(chuàng)建啟動(dòng)類

@SpringBootApplication
public class Spring5DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(Spring5DemoApplication.class, args);
    }
}

第六步：?jiǎn)?dòng)項(xiàng)目，訪問(wèn)如下兩個(gè)接口都可以

http://localhost:8080/api/test/hello
http://localhost:8080/add?args1=2&args2=3

通過(guò)上面的例子，我們看到基本的兩個(gè)類：HandlerFunction和RouterFunction，同時(shí)webflux有如下特性：

異步非阻塞

響應(yīng)式(reactive)函數(shù)編程，純lambda表達(dá)式

不僅僅是在Servlet容器中tomcat/jetty中運(yùn)行，同時(shí)支持NIO的Netty和Undertow中，實(shí)際項(xiàng)目中，我們往往與spring-boot項(xiàng)目結(jié)合，我們跟進(jìn)代碼可以看看spring-boot是在什么時(shí)候創(chuàng)建的server

一、SpringApplication

    public ConfigurableApplicationContext run(String... args) {
        StopWatch stopWatch = new StopWatch();
        stopWatch.start();
        ConfigurableApplicationContext context = null;
        Collection exceptionReporters = new ArrayList<>();
        configureHeadlessProperty();
        SpringApplicationRunListeners listeners = getRunListeners(args);
        listeners.starting();
        try {
            ApplicationArguments applicationArguments = new DefaultApplicationArguments(
                    args);
            ConfigurableEnvironment environment = prepareEnvironment(listeners,
                    applicationArguments);
            configureIgnoreBeanInfo(environment);
            Banner printedBanner = printBanner(environment);
            context = createApplicationContext();
            exceptionReporters = getSpringFactoriesInstances(
                    SpringBootExceptionReporter.class,
                    new Class[] { ConfigurableApplicationContext.class }, context);
            prepareContext(context, environment, listeners, applicationArguments,
                    printedBanner);
            refreshContext(context);
            afterRefresh(context, applicationArguments);
            stopWatch.stop();
            if (this.logStartupInfo) {
                new StartupInfoLogger(this.mainApplicationClass)
                        .logStarted(getApplicationLog(), stopWatch);
            }
            listeners.started(context);
            callRunners(context, applicationArguments);
        }
        catch (Throwable ex) {
            handleRunFailure(context, ex, exceptionReporters, listeners);
            throw new IllegalStateException(ex);
        }

        try {
            listeners.running(context);
        }
        catch (Throwable ex) {
            handleRunFailure(context, ex, exceptionReporters, null);
            throw new IllegalStateException(ex);
        }
        return context;
    }

我們只分析入口，其它代碼暫時(shí)不管，找到refreshContext(context);這一行進(jìn)去

二、ReactiveWebServerApplicationContext的refresh()

    @Override
    public final void refresh() throws BeansException, IllegalStateException {
        try {
            super.refresh();
        }
        catch (RuntimeException ex) {
            stopAndReleaseReactiveWebServer();
            throw ex;
        }
    }

三、ReactiveWebServerApplicationContext的onRefresh()

    @Override
    protected void onRefresh() {
        super.onRefresh();
        try {
            createWebServer();
        }
        catch (Throwable ex) {
            throw new ApplicationContextException("Unable to start reactive web server",
                    ex);
        }
    }

四、看到這里我們就找到入口方法了：createWebServer(),跟進(jìn)去，找到NettyReactiveWebServerFactory中創(chuàng)建webserver

    @Override
    public WebServer getWebServer(HttpHandler httpHandler) {
        HttpServer httpServer = createHttpServer();
        ReactorHttpHandlerAdapter handlerAdapter = new ReactorHttpHandlerAdapter(
                httpHandler);
        return new NettyWebServer(httpServer, handlerAdapter, this.lifecycleTimeout);
    }

看到ReactorHttpHandlerAdapter這個(gè)類想必特別親切，在開篇說(shuō)過(guò)是spring-cloud-gateway的入口，createHttpServer方法的細(xì)節(jié)暫時(shí)沒有去學(xué)習(xí)了，后續(xù)有時(shí)間去深入了解下

spring5的相關(guān)新特性也是在學(xué)習(xí)中，這一篇文章算是和springboot結(jié)合的入門吧，后續(xù)有時(shí)間再深入學(xué)習(xí)

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