SpringBoot2使用WebFlux函数式编程的方法

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，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。

新建项目

创建一个项目，pom文件中引入webflux依赖，完整pom文件如下：

<?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>

  <groupId>com.dalaoyang</groupId>
  <artifactId>springboot2_webflux</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>springboot2_webflux</name>
  <description>springboot2_webflux</description>

  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.3.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
  </parent>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <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-test</artifactId>
      <scope>test</scope>
    </dependency>

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

  <build>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
      </plugin>
    </plugins>
  </build>

</project>

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;

/**
 * @author dalaoyang
 * @project springboot_learn
 * @package com.dalaoyang.controller
 * @email yangyang@dalaoyang.cn
 * @date 2018/7/30
 */
@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;

/**
 * @author dalaoyang
 * @project springboot_learn
 * @package com.dalaoyang.handler
 * @email yangyang@dalaoyang.cn
 * @date 2018/7/30
 */
@Component
public class HiHandler {

  public Mono<ServerResponse> 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<String, ResponseCookie> cookies();

  Mono<Void> 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<HttpMessageWriter<?>> messageWriters();

    List<ViewResolver> viewResolvers();
  }

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

    ServerResponse.BodyBuilder contentType(MediaType var1);

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

    <T, P extends Publisher<T>> Mono<ServerResponse> body(P var1, Class<T> var2);

    <T, P extends Publisher<T>> Mono<ServerResponse> body(P var1, ParameterizedTypeReference<T> var2);

    Mono<ServerResponse> syncBody(Object var1);

    Mono<ServerResponse> body(BodyInserter<?, ? super ServerHttpResponse> var1);

    Mono<ServerResponse> render(String var1, Object... var2);

    Mono<ServerResponse> render(String var1, Map<String, ?> var2);
  }

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

    B headers(Consumer<HttpHeaders> var1);

    B cookie(ResponseCookie var1);

    B cookies(Consumer<MultiValueMap<String, ResponseCookie>> var1);

    B allow(HttpMethod... var1);

    B allow(Set<HttpMethod> var1);

    B eTag(String var1);

    B lastModified(ZonedDateTime var1);

    B location(URI var1);

    B cacheControl(CacheControl var1);

    B varyBy(String... var1);

    Mono<ServerResponse> build();

    Mono<ServerResponse> build(Publisher<Void> var1);

    Mono<ServerResponse> build(BiFunction<ServerWebExchange, ServerResponse.Context, Mono<Void>> var1);
  }
}

在回过头了看上面官方文档的图片，还需要配置一个路由来类似@RequestMapping的功能，通过RouterFunctions.route(RequestPredicate, HandlerFunction)提供了一个路由器函数默认实现，新建一个HiRouter，代码如下：

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;
/**
 * @author dalaoyang
 * @project springboot_learn
 * @package com.dalaoyang.router
 * @email yangyang@dalaoyang.cn
 * @date 2018/7/30
 */
@Configuration
public class HiRouter {
  @Bean
  public RouterFunction<ServerResponse> routeCity(HiHandler hiHandler) {
    return RouterFunctions
        .route(RequestPredicates.GET("/hi")
                .and(RequestPredicates.accept(MediaType.APPLICATION_JSON)),
            hiHandler::Hi);
  }
}

启动项目，通过控制台可以看到，两种方式的映射都被打印出来了，如图所示：

在浏览器访问，http://localhost:8080/hi,结果如图所示:

源码下载 ：大老杨码云

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