# 27.2 Spring WebFlux框架

Spring WebFlux是Spring Framework 5.0中引入的新的响应式网络框架。不同与Spring MVC，它不需要Servlet API，是完全异步、非阻塞的，通过[Reactor项目](https://projectreactor.io/)实现了[Reactive Streams](http://www.reactive-streams.org/) 规范。

Spring WebFlux有两种风格：函数式和基于注解。基于注解的风格相当接近于Spring MVC模型，如下所示：

```java
@RestController
@RequestMapping("/users")
public class MyRestController {

    @GetMapping("/{user}")
    public Mono<User> getUser(@PathVariable Long user) {
        // ...
    }

    @GetMapping("/{user}/customers")
    public Flux<Customer> getUserCustomers(@PathVariable Long user) {
        // ...
    }

    @DeleteMapping("/{user}")
    public Mono<User> deleteUser(@PathVariable Long user) {
        // ...
    }

}
```

“WebFlux.fn”——函数式变体，从请求的实际处理中分离了路由配置，如下所示：

```java
@Configuration
public class RoutingConfiguration {

    @Bean
    public RouterFunction<ServerResponse> monoRouterFunction(UserHandler userHandler) {
        return route(GET("/{user}").and(accept(APPLICATION_JSON)), userHandler::getUser)
                .andRoute(GET("/{user}/customers").and(accept(APPLICATION_JSON)), userHandler::getUserCustomers)
                .andRoute(DELETE("/{user}").and(accept(APPLICATION_JSON)), userHandler::deleteUser);
    }

}

@Component
public class UserHandler {

    public Mono<ServerResponse> getUser(ServerRequest request) {
        // ...
    }

    public Mono<ServerResponse> getUserCustomers(ServerRequest request) {
        // ...
    }

    public Mono<ServerResponse> deleteUser(ServerRequest request) {
        // ...
    }
}
```

WebFlux是Spring框架的一部分。详细信息请查看它的[参考文档](https://docs.spring.io/spring/docs/5.0.4.RELEASE/spring-framework-reference/web-reactive.html#webflux-fn)。

**注** 你可以定义多个`RouterFunction` bean来模块化路由的定义。如果你需要应用优先级，可以给bean排序。

给你的应用添加`spring-boot-starter-webflux`模块，开始使用。

**注** 在你的应用里同时添加`spring-boot-starter-web`和`spring-boot-starter-webflux`模块，会使Spring Boot自动配置Spring MVC，而不是WebFlux。这种行为是因为许多Spring开发者为了使用响应式的`WebClient`，往他们的Spring MVC应用里添加`spring-boot-starter-webflux`。你可以设置应用类型为`SpringApplication.setWebApplicationType(WebApplicationType.REACTIVE)`，强制Spring Boot自动配置WebFlux。


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