SpringBoot系列：基于SpringBoot2.0的WebFlux应用入门

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Spring WebFlux是在Spring框架5中引入的一种新的反应式Web框架。与Spring MVC不同，它不需要servlet API，完全异步和非阻塞，并通过Reactive Project实现Reactive Streams规范。

官网文档地址：

https://docs.spring.io/spring/docs/5.0.5.RELEASE/spring-framework-reference/web-reactive.html#webflux

1、创建一个SpringBoot2.0项目

Eclipse中创建Maven工程，也可以使用Spring Initializer创建，在Pom.xml中添加依赖：

注意：SpringBoot2.0仅支持JDK8.0以上，不支持JDK6、JDK7

<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.sample</groupId><artifactId>sun-sample-springboot-webflux</artifactId><version>0.0.1-SNAPSHOT</version><dependencyManagement><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-dependencies</artifactId><version>2.0.1.RELEASE</version><type>pom</type><scope>import</scope></dependency></dependencies></dependencyManagement><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-data-jpa</artifactId></dependency><dependency><groupId>com.h2database</groupId><artifactId>h2</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>

Spring-boot-starter-webflux 将 spring-webflux、netty 以及其他必须的依赖包引入到类路径中。

h2database 是h2内存数据库，用于快速测试

jpa 是ORM操作，快速编写CRUD

工程主函数代码如下：

package com.suncht.sample;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplication
public class WebfluxApplication {public static void main(String[] args) {SpringApplication.run(WebfluxApplication.class, args);}
}

application.properties属性文件配置如下：

server.port=8080spring.datasource.url=jdbc:h2:file:D\:/h2/h2test;AUTO_SERVER=TRUE;DB_CLOSE_DELAY=-1
spring.datasource.driver-class-name=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
spring.jpa.hibernate.ddl-auto=update
spring.jpa.properties.hibernate.show_sql=true
spring.jpa.properties.hibernate.use_sql_comments=true
spring.jpa.properties.hibernate.format_sql=truespring.h2.console.enabled=true
spring.h2.console.path=/console
spring.h2.console.settings.trace=false
spring.h2.console.settings.web-allow-others=false#logging.level.root=debug

2、创建 HttpServer

package com.suncht.sample.config;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.env.Environment;
import org.springframework.http.server.reactive.HttpHandler;
import org.springframework.http.server.reactive.ReactorHttpHandlerAdapter;
import org.springframework.web.reactive.function.server.RouterFunction;
import org.springframework.web.reactive.function.server.RouterFunctions;import reactor.ipc.netty.http.server.HttpServer;/*** 配置HttpServer* 可以配置基于Netty、基于Tomcat、基于Jetty* @author suncht**/
@Configuration
public class HttpServerConfig {@Autowiredprivate Environment environment;@Beanpublic HttpServer httpServer(RouterFunction<?> routerFunction) {HttpHandler httpHandler = RouterFunctions.toHttpHandler(routerFunction);ReactorHttpHandlerAdapter adapter = new ReactorHttpHandlerAdapter(httpHandler);HttpServer server = HttpServer.create("localhost", Integer.valueOf(environment.getProperty("server.port")));server.newHandler(adapter);return server;}
}

这个根据应用配置中指定的端口创建一个 Netty HttpServer 服务器。Spring 支持例如 Tomcat 或者 Undertow 等其他服务器。因为 Netty 本身是异步的和事件驱动的，因此它更适合用来运行 Reactive 应用。而 Tomcat 使用 Java NIO 来实现 Servlet 规范。Netty 的 NIO 实现专门针对异步、事件驱动和非堵塞应用进行了优化。

3、编写Http请求的业务逻辑

WebFlux 支持两种编程：

（1）使用@Controller这种基于注解的姿势, 与Sring MVC的姿势相同，最简单最简洁

（2）基于Java 8 Lambda的函数式编程风格，需要编写Handler和Router

第一方式：基于注解

package com.suncht.sample.controller;import java.util.List;
import java.util.Optional;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import com.suncht.sample.model.User;
import com.suncht.sample.service.UserRepository;/*** WebFlux的第一种方式： annotation-based（注解）* @author suncht**/
@RestController
@RequestMapping("/users")
public class UserRestController {@Autowiredprivate UserRepository userRepository;@GetMapping("/")public List<User> getAllUser() {return userRepository.findAll();}@GetMapping("/{id}")public User getUser(@PathVariable Long id) {Optional<User> user = userRepository.findById(id);return user.get();}@GetMapping("/add/{userName}/{age}")public Long getUser(@PathVariable("userName") String userName, @PathVariable("age") Integer age) {User user = new User();user.setUserName(userName);user.setAge(age);User result = userRepository.save(user);return result.getId();}}

第二种方式：基于函数

package com.suncht.sample.handler;import java.util.Optional;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.reactive.function.server.ServerRequest;
import org.springframework.web.reactive.function.server.ServerResponse;import com.suncht.sample.model.User;
import com.suncht.sample.service.UserRepository;import reactor.core.publisher.Mono;/*** UserHandler* 用户操作的业务逻辑* @author suncht**/
@Service
public class UserHandler {@Autowiredprivate UserRepository userRepository;public Mono<ServerResponse> handleGetUserById(ServerRequest request) {Long userId = Long.valueOf(request.pathVariable("id"));Optional<User> user = userRepository.findById(userId);return ServerResponse.ok().body(Mono.just(user.get()), User.class).switchIfEmpty(ServerResponse.notFound().build());}	
}

这是针对用户的handler，其实就是用户的业务逻辑操作而已。跟我们平时写的业务逻辑不同是：返回对象Mono和Flux。

关于Mono和Flux，请参考官网：https://docs.spring.io/spring/docs/5.0.5.RELEASE/spring-framework-reference/web-reactive.html#webflux-fn-handler-functions

package com.suncht.sample.route;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 com.suncht.sample.handler.UserHandler;/*** WebFlux的第二种方式： functional（java方法）* Router路由，其实就是用代码实现http请求路径，类似于Python Web框架django，手动编写路由代码* @author suncht**/
@Configuration
public class UserRouter {@Beanpublic RouterFunction<?> routerFunction(UserHandler userHandler) {return RouterFunctions.route(RequestPredicates.GET("/api/user/{id}").and(RequestPredicates.accept(MediaType.APPLICATION_JSON)), userHandler::handleGetUserById);}
}

这是用户http请求的路由规则，手动编写。较第一方法而言，比较麻烦。

4、测试

可以在浏览器中直接输入HTTP地址：http://127.0.0.1:8080/api/user/2 进行测试

也可以使用WebFlux中的WebClient测试，代码如下：

package com.suncht.sample.test;import java.util.List;import org.junit.Before;
import org.junit.Test;
import org.springframework.http.MediaType;
import org.springframework.web.reactive.function.client.WebClient;import com.suncht.sample.model.User;import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;public class WebTest {private WebClient client = null;@Beforepublic void init() {client = WebClient.create("http://127.0.0.1:8080/");}@Testpublic void testUserById() {Mono<User> result = client.get()// 请求方法,get,post....uri("users/{id}", "1")// 请求相对地址以及参数.accept(MediaType.APPLICATION_JSON).retrieve()// 请求类型.bodyToMono(User.class);// 返回类型User user = result.block();System.out.println(user);}@Testpublic void testUserById2() {Mono<User> result2 = client.get()// 请求方法,get,post....uri("api/user/{id}", "1")// 请求相对地址以及参数.accept(MediaType.APPLICATION_JSON).retrieve()// 请求类型.bodyToMono(User.class);// 返回类型User user2 = result2.block();System.out.println(user2);}@Testpublic void testAllUsers() {Flux<User> userFlux = client.get().uri("users/").accept(MediaType.APPLICATION_JSON).retrieve()// 请求类型.bodyToFlux(User.class);// 返回类型List<User> users = userFlux.collectList().block();System.out.println(users);}}

WebClient是远程调用Http请求的一种工具类、新思路

5、其他代码

User实体：

package com.suncht.sample.model;import java.io.Serializable;import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;@Entity
@Table(name = "t_user")
public class User implements Serializable {private static final long serialVersionUID = 1L;@Id@GeneratedValue(strategy = GenerationType.IDENTITY)private Long id;@Column(name="user_name", nullable=false, length=50)private String userName;@Column(name="age")private Integer age;public Long getId() {return id;}public void setId(Long id) {this.id = id;}public String getUserName() {return userName;}public void setUserName(String userName) {this.userName = userName;}public Integer getAge() {return age;}public void setAge(Integer age) {this.age = age;}@Overridepublic String toString() {return "User [id=" + id + ", userName=" + userName + ", age=" + age + "]";}}

针对User的JPA CRUD操作：

package com.suncht.sample.service;import org.springframework.data.jpa.repository.JpaRepository;import com.suncht.sample.model.User;public interface UserRepository extends JpaRepository<User, Long> {
}

6、整个工程项目结构预览