springboot(六)——springboot与webflux结合初探

摘要：的这几天看了看的请求处理流程，因为之前一直用的和，一开始对的处理流程有点懵逼，找不到入口，后来跟了代码，在网上找了点资料，发现的入口在的方法该方法的作用就是把接收到的或者最终需要返回的，包装转换为和。

这几天看了看spring-cloud-gateway的请求处理流程，因为之前一直用的springboot1.x和spring4，一开始对spring-cloud-gateway的处理流程有点懵逼，找不到入口，后来跟了代码，在网上找了点资料，发现spring-cloud-gateway的入口在ReactorHttpHandlerAdapter的apply方法

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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();
        }
    }
}

该方法的作用就是把接收到的HttpServerRequest或者最终需要返回的HttpServerResponse，包装转换为ReactorServerHttpRequest和ReactorServerHttpResponse。

当然，这篇文章的主要内容不是谈论spring-cloud-gateway了，因为之前一直用的spring4，所以对spring5当中的反应式编程范式和webflux不太了解，所以先写个demo了解一下
第一步：引入相关pom,测试的相关pom根据自己的需要引入

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        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：创建一个HandlerFunction

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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：注入一个RouterFunction

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@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注解的编程方式，我们也创建一个controller

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@RestController
@RequestMapping("/api/test")
public class HelloController {
    @RequestMapping("/hello")
    public Mono hello() {
        return Mono.just("hello world");
    }
}

第五步：创建启动类

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

第六步：启动项目，访问如下两个接口都可以

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

通过上面的例子，我们看到基本的两个类：HandlerFunction和RouterFunction，同时webflux有如下特性：

异步非阻塞

响应式(reactive)函数编程，纯lambda表达式

不仅仅是在Servlet容器中tomcat/jetty中运行，同时支持NIO的Netty和Undertow中，实际项目中，我们往往与spring-boot项目结合，我们跟进代码可以看看spring-boot是在什么时候创建的server

一、SpringApplication

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    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;
    }

我们只分析入口，其它代码暂时不管，找到refreshContext(context);这一行进去

二、ReactiveWebServerApplicationContext的refresh()

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

三、ReactiveWebServerApplicationContext的onRefresh()

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

四、看到这里我们就找到入口方法了：createWebServer(),跟进去，找到NettyReactiveWebServerFactory中创建webserver

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

看到ReactorHttpHandlerAdapter这个类想必特别亲切，在开篇说过是spring-cloud-gateway的入口，createHttpServer方法的细节暂时没有去学习了，后续有时间去深入了解下

spring5的相关新特性也是在学习中，这一篇文章算是和springboot结合的入门吧，后续有时间再深入学习

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