SpringBoot2使用WebFlux函数式编程

本文只是简单使用SpringBoot2使用WebFlux的函数式编程简单使用，后续会继续写关于Webflux相关的文章。

最近一直在研究WebFlux，后续会陆续出一些相关的文章。

首先看一下Srping官网上的一张图，对比一下SpringMvc和Spring WebFlux，如图：

在查看一下WebFlux的官方文档:https://docs.spring.io/spring/docs/current/spring-framework-reference/web-reactive.html#spring-webflux，WebFlux提供了函数式编程，本文简单介绍一下WebFlux函数式编程简单使用。

创建一个项目，pom文件中引入webflux依赖，完整pom文件如下：

    4.0.0

    com.dalaoyang
    springboot2_webflux
    0.0.1-SNAPSHOT
    jar

    springboot2_webflux
    springboot2_webflux

    
 org.springframework.boot
 spring-boot-starter-parent
 2.0.3.RELEASE
  
    

    
 UTF-8
 UTF-8
 1.8
    

    
 
     org.springframework.boot
     spring-boot-starter
 

 
     org.springframework.boot
     spring-boot-starter-test
     test
 

 
     org.springframework.boot
     spring-boot-starter-webflux
 
    

    
 
     
  org.springframework.boot
  spring-boot-maven-plugin
     
 
    

首先试试引入WebFlux依赖之后，SpringMvc方式是否还能使用，新建一个HelloController，完整代码如下，执行后发现，是可以正常执行访问的，这其实就是我们所说的注解式编程。

package com.dalaoyang.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;


@RestController
public class HelloController {

    @GetMapping("hello")
    public String Hello(){
 return "Hello this is SpringWebFlux";
    }


}

结果如图：

接下来使用函数式编程，首先查阅一下官方文档，如图：

我们需要创建一个HandlerFunction返回值为Mono，新建一个HiHandler，里面写一个方法Hi，完整代码如下：

package com.dalaoyang.handler;
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 HiHandler {


    public Mono Hi(ServerRequest request) {
 return ServerResponse.ok().contentType(MediaType.APPLICATION_JSON)
  .body(BodyInserters.fromObject("Hi , this is SpringWebFlux"));
    }
}

其中ServerResponse是相应的封装对象，下面是它的源码，其中包含了响应状态，响应头等等，代码如下：

package org.springframework.web.reactive.function.server;

import java.net.URI;
import java.time.ZonedDateTime;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import org.reactivestreams.Publisher;
import org.springframework.core.ParameterizedTypeReference;
import org.springframework.http.CacheControl;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.Responsecookie;
import org.springframework.http.codec.HttpMessageWriter;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.util.MultiValueMap;
import org.springframework.web.reactive.function.BodyInserter;
import org.springframework.web.reactive.result.view.ViewResolver;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Mono;

public interface ServerResponse {
    HttpStatus statusCode();

    HttpHeaders headers();

    MultiValueMap cookies();

    Mono writeTo(ServerWebExchange var1, ServerResponse.Context var2);

    static ServerResponse.BodyBuilder from(ServerResponse other) {
 return new DefaultServerResponseBuilder(other);
    }

    static ServerResponse.BodyBuilder status(HttpStatus status) {
 return new DefaultServerResponseBuilder(status);
    }

    static ServerResponse.BodyBuilder status(int status) {
 return new DefaultServerResponseBuilder(status);
    }

    static ServerResponse.BodyBuilder ok() {
 return status(HttpStatus.OK);
    }

    static ServerResponse.BodyBuilder created(URI location) {
 ServerResponse.BodyBuilder builder = status(HttpStatus.CREATED);
 return (ServerResponse.BodyBuilder)builder.location(location);
    }

    static ServerResponse.BodyBuilder accepted() {
 return status(HttpStatus.ACCEPTED);
    }

    static ServerResponse.HeadersBuilder noContent() {
 return status(HttpStatus.NO_CONTENT);
    }

    static ServerResponse.BodyBuilder seeOther(URI location) {
 ServerResponse.BodyBuilder builder = status(HttpStatus.SEE_OTHER);
 return (ServerResponse.BodyBuilder)builder.location(location);
    }

    static ServerResponse.BodyBuilder temporaryRedirect(URI location) {
 ServerResponse.BodyBuilder builder = status(HttpStatus.TEMPORARY_REDIRECT);
 return (ServerResponse.BodyBuilder)builder.location(location);
    }

    static ServerResponse.BodyBuilder permanentRedirect(URI location) {
 ServerResponse.BodyBuilder builder = status(HttpStatus.PERMANENT_REDIRECT);
 return (ServerResponse.BodyBuilder)builder.location(location);
    }

    static ServerResponse.BodyBuilder badRequest() {
 return status(HttpStatus.BAD_REQUEST);
    }

    static ServerResponse.HeadersBuilder notFound() {
 return status(HttpStatus.NOT_FOUND);
    }

    static ServerResponse.BodyBuilder unprocessableEntity() {
 return status(HttpStatus.UNPROCESSABLE_ENTITY);
    }

    public interface Context {
 List> messageWriters();

 List viewResolvers();
    }

    public interface BodyBuilder extends ServerResponse.HeadersBuilder {
 ServerResponse.BodyBuilder contentLength(long var1);

 ServerResponse.BodyBuilder contentType(MediaType var1);

 ServerResponse.BodyBuilder hint(String var1, Object var2);

 > Mono body(P var1, Class var2);

 > Mono body(P var1, ParameterizedTypeReference var2);

 Mono syncBody(Object var1);

 Mono body(BodyInserter var1);

 Mono render(String var1, Object... var2);

 Mono render(String var1, Map var2);
    }

    public interface HeadersBuilder> {
 B header(String var1, String... var2);

 B headers(Consumer var1);

 B cookie(Responsecookie var1);

 B cookies(Consumer> var1);

 B allow(HttpMethod... var1);

 B allow(Set var1);

 B eTag(String var1);

 B lastModified(ZonedDateTime var1);

 B location(URI var1);

 B cacheControl(CacheControl var1);

 B varyBy(String... var1);

 Mono build();

 Mono build(Publisher var1);

 Mono build(BiFunction> var1);
    }
}

package com.dalaoyang.router;

import com.dalaoyang.handler.HiHandler;
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 HiRouter {
    @Bean
    public RouterFunction routeHi(HiHandler hiHandler) {
 return RouterFunctions
  .route(RequestPredicates.GET("/hi")
    .and(RequestPredicates.accept(MediaType.APPLICATION_JSON)),
   hiHandler::Hi);
    }
}