springboot(六)——springboot與webflux結合初探

時間 2019-12-13

原文原文鏈接

spring-cloud-gateway 的ReactorHttpHandlerAdapter

這幾天看了看spring-cloud-gateway的請求處理流程，由於以前一直用的springboot1.x和spring4，一開始對spring-cloud-gateway的處理流程有點懵逼，找不到入口，後來跟了代碼，在網上找了點資料，發現spring-cloud-gateway的入口在ReactorHttpHandlerAdapter的apply方法java

public class ReactorHttpHandlerAdapter implements BiFunction<HttpServerRequest, HttpServerResponse, Mono<Void>> {

    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<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();
        }
    }

}

該方法的做用就是把接收到的HttpServerRequest或者最終須要返回的HttpServerResponse，包裝轉換爲ReactorServerHttpRequest和ReactorServerHttpResponse。react

spring-webflux

固然，這篇文章的主要內容不是談論spring-cloud-gateway了，由於以前一直用的spring4，因此對spring5當中的反應式編程範式和webflux不太瞭解，因此先寫個demo瞭解一下
第一步：引入相關pom,測試的相關pom根據本身的須要引入web

<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>


    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-webflux</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>io.projectreactor</groupId>
            <artifactId>reactor-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

第二步：建立一個HandlerFunctionspring

public class TestFunction implements HandlerFunction<ServerResponse> {

    @Override
    public Mono<ServerResponse> 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RouterFunction編程

@Configuration
public class TestRouteFunction {

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

第四步：在webflux中，也可使用以前的java註解的編程方式，咱們也建立一個controllerapi

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

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

第五步：建立啓動類tomcat

@SpringBootApplication
public class Spring5DemoApplication {

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

第六步：啓動項目，訪問以下兩個接口均可以springboot

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

和spring-boot結合

經過上面的例子，咱們看到基本的兩個類：HandlerFunction和RouterFunction，同時webflux有以下特性：app

異步非阻塞
響應式(reactive)函數編程，純lambda表達式
不單單是在Servlet容器中tomcat/jetty中運行，同時支持NIO的Netty和Undertow中，實際項目中，咱們每每與spring-boot項目結合，咱們跟進代碼能夠看看spring-boot是在何時建立的server

1、SpringApplicationless

public ConfigurableApplicationContext run(String... args) {
        StopWatch stopWatch = new StopWatch();
        stopWatch.start();
        ConfigurableApplicationContext context = null;
        Collection<SpringBootExceptionReporter> 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;
    }

咱們只分析入口，其它代碼暫時無論，找到refreshContext(context);這一行進去

2、ReactiveWebServerApplicationContext的refresh()

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

3、ReactiveWebServerApplicationContext的onRefresh()

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

4、看到這裏咱們就找到入口方法了：createWebServer(),跟進去，找到NettyReactiveWebServerFactory中建立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這個類想必特別親切，在開篇說過是spring-cloud-gateway的入口，createHttpServer方法的細節暫時沒有去學習了，後續有時間去深刻了解下