本文只是簡單使用SpringBoot2使用WebFlux的函數語言程式設計簡單使用，後續會繼續寫關於Webflux相關的文章。

最近一直在研究WebFlux，後續會陸續出一些相關的文章。

首先看一下Srping官網上的一張圖，對比一下SpringMvc和Spring WebFlux，如圖：

在檢視一下WebFlux的官方文件:https://docs.spring.io/spring/docs/current/spring-framework-reference/web-reactive.html#spring-webflux，WebFlux提供了函數語言程式設計，本文簡單介紹一下WebFlux函數語言程式設計簡單使用。

新建專案

建立一個專案，pom檔案中引入webflux依賴，完整pom檔案如下：

<?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>

首先試試引入WebFlux依賴之後，SpringMvc方式是否還能使用，新建一個HelloController，完整程式碼如下，執行後發現，是可以正常執行訪問的，這其實就是我們所說的註解式程式設計。

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 [email protected]
 * @date 2018/7/30
 */
@RestController
public class HelloController {

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


}

結果如圖：

接下來使用函數語言程式設計，首先查閱一下官方文件，如圖：

我們需要建立一個HandlerFunction返回值為Mono，新建一個HiHandler，裡面寫一個方法Hi，完整程式碼如下：

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 [email protected]
 * @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是相應的封裝物件，下面是它的原始碼，其中包含了響應狀態，響應頭等等，程式碼如下：

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);
    }
}

在回過頭了看上面官方文件的圖片，還需要配置一個路由來類似@RequestMapping的功能，通過RouterFunctions.route(RequestPredicate, HandlerFunction)提供了一個路由器函式預設實現，新建一個HiRouter，程式碼如下：

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 [email protected]
 * @date 2018/7/30
 */
@Configuration
public class HiRouter {
    @Bean
    public RouterFunction<ServerResponse> routeHi(HiHandler hiHandler) {
        return RouterFunctions
                .route(RequestPredicates.GET("/hi")
                                .and(RequestPredicates.accept(MediaType.APPLICATION_JSON)),
                        hiHandler::Hi);
    }
}

啟動專案，通過控制檯可以看到，兩種方式的對映都被打印出來了，如圖所示：

在瀏覽器訪問，http://localhost:8080/hi,結果如圖所示:

原始碼下載 ：大老楊碼雲

個人網站：https://www.dalaoyang.cn

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