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spring boot整合spring5-webflux从0开始的实战及源码解析

一天不进步,就是退步 2019-02-20 16:42:00 阅读数:229 评论数:0 点赞数:0 收藏数:0

上篇文章<你的响应阻塞了没有?--Spring-WebFlux源码分析>介绍了spring5.0 新出来的异步非阻塞服务,很多读者说太理论了,太单调了,这次我们就通过一个从0开始的实例实战一下。

1.准备工作

   spring 提供的IDE工STS,配置好maven即可

2.创建spring boot start项目spring5-webflux,并添加依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.3.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>spring5-webflux</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>spring5-webflux</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
 </dependency>
<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>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

3.增加处理器HelloWorldHandler

package com.example.demo;
import org.springframework.http.MediaType;
import org.springframework.stereotype.Component;
import org.springframework.web.reactive.function.BodyInserters;
import org.springframework.web.reactive.function.server.ServerRequest;
import org.springframework.web.reactive.function.server.ServerResponse;
import reactor.core.publisher.Mono;
@Component
public class HelloWorldHandler {
public Mono<ServerResponse> helloWorld(ServerRequest request) {
return ServerResponse.ok().contentType(MediaType.TEXT_PLAIN)
.body(BodyInserters.fromObject("Hello World!"));
}
}

4.增加路由器,对应HandlerFunction

package com.example.demo;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.MediaType;
import org.springframework.web.reactive.function.server.RequestPredicates;
import org.springframework.web.reactive.function.server.RouterFunction;
import org.springframework.web.reactive.function.server.RouterFunctions;
import org.springframework.web.reactive.function.server.ServerResponse;
@Configuration
public class HelloWorldRouter {
@Bean
public RouterFunction<ServerResponse> routeHelloWorld(HelloWorldHandler helloWorldHandler) {
return RouterFunctions
.route(RequestPredicates.GET("/helloWorld").and(RequestPredicates.accept(MediaType.TEXT_PLAIN)), helloWorldHandler::helloWorld);
}
}

默认启动时,提供了DefaultRouterFunction的实例

 /**
* Route to the given handler function if the given request predicate applies.
* <p>For instance, the following example routes GET requests for "/user" to the
* {@code listUsers} method in {@code userController}:
* <pre class="code">
* RouterFunction&lt;ServerResponse&gt; route =
* RouterFunctions.route(RequestPredicates.GET("/user"), userController::listUsers);
* </pre>
* @param predicate the predicate to test
* @param handlerFunction the handler function to route to if the predicate applies
* @param <T> the type of response returned by the handler function
* @return a router function that routes to {@code handlerFunction} if
* {@code predicate} evaluates to {@code true}
* @see RequestPredicates
*/
public static <T extends ServerResponse> RouterFunction<T> route(
RequestPredicate predicate, HandlerFunction<T> handlerFunction) {
return new DefaultRouterFunction<>(predicate, handlerFunction);
}

5.启动spring boot项目,调试进入DispatchHandler

 @Override
public Mono<Void> handle(ServerWebExchange exchange) {
if (this.handlerMappings == null) {
return createNotFoundError();
}
return Flux.fromIterable(this.handlerMappings)
.concatMap(mapping -> mapping.getHandler(exchange))
.next()
.switchIfEmpty(createNotFoundError())
.flatMap(handler -> invokeHandler(exchange, handler))
.flatMap(result -> handleResult(exchange, result));
}

此时HandlerMapping已经初始化完成

   5.1 获取Handler

AbstractHandlerMapping.java 

 @Override
public Mono<Object> getHandler(ServerWebExchange exchange) {
return getHandlerInternal(exchange).map(handler -> {
if (logger.isDebugEnabled()) {
logger.debug(exchange.getLogPrefix() + "Mapped to " + handler);
}
if (CorsUtils.isCorsRequest(exchange.getRequest())) {
CorsConfiguration configA = this.corsConfigurationSource.getCorsConfiguration(exchange);
CorsConfiguration configB = getCorsConfiguration(handler, exchange);
CorsConfiguration config = (configA != null ? configA.combine(configB) : configB);
if (!getCorsProcessor().process(config, exchange) ||
CorsUtils.isPreFlightRequest(exchange.getRequest())) {
return REQUEST_HANDLED_HANDLER;
}
}
return handler;
});
}

通过RouterFunctions获取HandlerAdapter

 

 5.2 执行HandlerAdapter

 

 HelloWorldHandler的类型是HandlerFunctionAdapter类型,触发HandlerFunctionAdapter执行handle方法

 @Override
public Mono<HandlerResult> handle(ServerWebExchange exchange, Object handler) {
HandlerFunction<?> handlerFunction = (HandlerFunction<?>) handler;
ServerRequest request = exchange.getRequiredAttribute(RouterFunctions.REQUEST_ATTRIBUTE);
return handlerFunction.handle(request)
.map(response -> new HandlerResult(handlerFunction, response, HANDLER_FUNCTION_RETURN_TYPE));
}

最后调用HelloWorldHandler的helloWorld方法

@Component
public class HelloWorldHandler {
public Mono<ServerResponse> helloWorld(ServerRequest request) {
return ServerResponse.ok().contentType(MediaType.TEXT_PLAIN)
.body(BodyInserters.fromObject("Hello World!"));
}
}

5.3 执行HandleResult

 private Mono<Void> handleResult(ServerWebExchange exchange, HandlerResult result) {
return getResultHandler(result).handleResult(exchange, result)
.onErrorResume(ex -> result.applyExceptionHandler(ex).flatMap(exceptionResult ->
getResultHandler(exceptionResult).handleResult(exchange, exceptionResult)));
}

因HelloWorldRouter返回结果类型是ServerResponse,故调用ServerResponseResultHandler来处理结果

 @Override
public Mono<Void> handleResult(ServerWebExchange exchange, HandlerResult result) {
ServerResponse response = (ServerResponse) result.getReturnValue();
Assert.state(response != null, "No ServerResponse");
return response.writeTo(exchange, new ServerResponse.Context() {
@Override
public List<HttpMessageWriter<?>> messageWriters() {
return messageWriters;
}
@Override
public List<ViewResolver> viewResolvers() {
return viewResolvers;
}
});
}

6.总结

   spring mvc和spring webflux是一对兄弟,他们的处理流程类似,mvc是同步阻塞服务,webflux是异步非阻塞服务,它们直接的关系如下:

     spring webflux 增加了functional endpoint,RouterFunction(RouterFunctions构建)等同于HanderMapping, HandlerFunction(HandlerFunctionAdapter继承自HandlerAdapter来代理)等同于HandlerAdapter

    spring webflux 引入了spring boot2,Reactor,lambda表达式,语法更简洁,但可读性变弱。

参考文献:

【1】https://www.journaldev.com/20763/spring-webflux-reactive-programming

版权声明
本文为[一天不进步,就是退步]所创,转载请带上原文链接,感谢
https://www.cnblogs.com/davidwang456/p/10407557.html

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