Spring WebFlux is the new module introduced in Spring 5. Spring WebFlux is the first step towards reactive programming model in spring framework.
Spring WebFlux是Spring 5中引入的新模块。SpringWebFlux是向Spring框架中的React式编程模型迈出的第一步。
弹簧React式编程 (Spring Reactive Programming)
If you are new to reactive programming model, then I would highly suggest you to go through following articles to learn about reactive programming.
如果您不熟悉React式编程模型，那么我强烈建议您阅读以下文章以了解React式编程。
If you are new to Spring 5, please go through .
如果您不熟悉Spring 5，请参阅 。
SpringWebFlux (Spring WebFlux)
Spring WebFlux is the alternative to module. Spring WebFlux is used to create fully asynchronous and non-blocking application built on event-loop execution model.
Spring WebFlux是模块的替代方案。 Spring WebFlux用于创建基于事件循环执行模型的完全异步且非阻塞的应用程序。
Below diagram from Spring Official Documentation provides great insight on comparison of Spring WebFlux to Spring Web MVC.
Spring官方文档中的下图提供了关于Spring WebFlux与Spring Web MVC比较的深刻见解。
If you are looking to develop a web application or Rest web service on non-blocking reactive model, then you can look into Spring WebFlux.
Spring WebFlux is built on . Project Reactor is the implementation of Reactive Streams specification. Reactor provides two types:
Spring WebFlux基于构建。 Project Reactor是Reactive Streams规范的实现。 Reactor提供两种类型：
Mono: implements Publisher and returns 0 or 1 elements Mono ：实现Publisher，并返回0或1个元素
Flux: implements Publisher and returns N elements. Flux ：实现Publisher，并返回N个元素。
Spring WebFlux Hello World示例 (Spring WebFlux Hello World Example)
Let’s built a simple Spring WebFlux Hello World application. We will create a simple rest web service and use Spring Boot to run it on default Netty server.
Our final project structure looks like below image.
我们的最终项目结构如下图所示。
Let’s look into each component of the application one by one.
让我们逐一研究应用程序的每个组件。
Spring WebFlux Maven依赖关系 (Spring WebFlux Maven Dependencies)
4.0.0 com.journaldev.spring SpringWebflux 0.0.1-SNAPSHOT Spring WebFlux Spring WebFlux Example UTF-8 UTF-8 1.9 org.springframework.boot spring-boot-starter-parent 2.0.1.RELEASE org.springframework.boot spring-boot-starter-webflux org.springframework.boot spring-boot-starter-test test io.projectreactor reactor-test test spring-snapshots Spring Snapshots https://repo.spring.io/snapshot true spring-milestones Spring Milestones https://repo.spring.io/milestone false spring-snapshots Spring Snapshots https://repo.spring.io/snapshot true spring-milestones Spring Milestones https://repo.spring.io/milestone false org.springframework.boot spring-boot-maven-plugin org.apache.maven.plugins maven-compiler-plugin 3.7.0 ${jdk.version} ${jdk.version}
The most important dependencies are spring-boot-starter-webflux and spring-boot-starter-parent. Some other dependencies are for creating JUnit test cases.
Notice that reactive component Mono holds the ServerResponse body. Also look at the function chain to set the return content type, response code and body.
So we are exposing a GET method for /helloWorld and the client call should accept plain text response.
因此，我们公开了/helloWorld的GET方法，并且客户端调用应接受纯文本响应。
Spring Boot应用程序 (Spring Boot Application)
Let’s configure our simple WebFlux application with Spring Boot.
让我们使用Spring Boot配置我们的简单WebFlux应用程序。
package com.journaldev.spring;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplicationpublic class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); }}
If you look at above code, there is nothing related to Spring WebFlux. But Spring Boot will configure our application as Spring WebFlux since we have added dependency of spring-boot-starter-webflux module.
运行Spring WebFlux Spring Boot App (Running the Spring WebFlux Spring Boot App)
If you have Spring support in Eclipse, then you can run above class as Spring Boot App.
如果您在Eclipse中具有Spring支持，则可以在类之上运行Spring Boot App。
If you like to use command line, then open terminal and run command mvn spring-boot:run from the project source directory.
如果要使用命令行，请打开终端，然后从项目源目录运行命令mvn spring-boot:run 。
Once the app is running, notice following log messages to make sure everything is good with our app. It’s also helpful when you extend this simple app by adding more routes and functionalities.
Here is a JUnit test program to test our Rest web service using WebTestClient from Spring 5 reactive web.
package com.journaldev.spring;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.test.context.SpringBootTest;import org.springframework.http.MediaType;import org.springframework.test.context.junit4.SpringRunner;import org.springframework.test.web.reactive.server.WebTestClient;@RunWith(SpringRunner.class)@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)public class SpringWebFluxTest { @Autowired private WebTestClient webTestClient; @Test public void testHelloWorld() { webTestClient .get().uri("/helloWorld") // GET method and URI .accept(MediaType.TEXT_PLAIN) //setting ACCEPT-Content .exchange() //gives access to response .expectStatus().isOk() //checking if response is OK .expectBody(String.class).isEqualTo("Hello World!"); // checking for response type and message }}
Run it a JUnit test case and it should pass with flying colors.
package com.journaldev.spring;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.test.context.SpringBootTest;import org.springframework.http.MediaType;import org.springframework.test.context.junit4.SpringRunner;import org.springframework.test.web.reactive.server.WebTestClient;@RunWith(SpringRunner.class)@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)public class SpringWebFluxTest { @Autowired private WebTestClient webTestClient; @Test public void testHelloWorld() { webTestClient .get().uri("/helloWorld") // GET method and URI .accept(MediaType.TEXT_PLAIN) //setting ACCEPT-Content .exchange() //gives access to response .expectStatus().isOk() //checking if response is OK .expectBody(String.class).isEqualTo("Hello World!"); // checking for response type and message }}
It’s good to see that popular frameworks such as Spring are rooting for reactive programming model. But we have a lot to cover because if all your dependencies are not reactive and non-blocking then your application is also not truly reactive.
For example, relational database vendors doesn’t have reactive drivers because they depend on JDBC, that is not reactive. Hence Hibernate API is also non-reactive. So if you are using relational databases then you can’t built a truly reactive application, yet. I am hopeful that it will change sooner than later.