springboot(六)——springboot與webflux結合初探

時間 2019-12-12

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();
		}
	}

}

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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>
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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"));
    }
}

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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());
    }
}
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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");
    }
}
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第五步：建立啓動類tomcat

@SpringBootApplication
public class Spring5DemoApplication {

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

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、SpringApplication

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

2、ReactiveWebServerApplicationContext的refresh()

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