Spring Boot RouterFunction tutorial
last modified July 6, 2020
Spring Boot RouterFunction tutorial shows how to create functional routes in Spring Boot applications.
Reactive programming
Reactive programming is a programming paradigm that is functional, event-based, non-blocking, asynchronous, and centered around data stream processing. The term reactive comes from the fact that we react to changes such as mouse clicks or I/O events.
Traditional Spring MVC applications use annotations such as @GetMapping
to map request paths to controller actions. Functional routing API is an alternative
way of this mapping.
RouterFunction
RouterFunction
represents a function that routes to
a handler function.
Spring Boot RouterFunction example
In the following application we create a reactive Spring Boot application with functional routes.
pom.xml src ├───main │ ├───java │ │ └───com │ │ └───zetcode │ │ │ Application.java │ │ └───routes │ │ MyRoutes.java │ └───resources └───test └───java └───com └───zetcode └───routes MyRoutesTest.java
This is the project structure of the Spring application.
<?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.zetcode</groupId> <artifactId>springbootrouterfunction</artifactId> <version>1.0-SNAPSHOT</version> <packaging>jar</packaging> <properties> <java.version>13</java.version> </properties> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.2.4.RELEASE</version> </parent> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-webflux</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>
This is the Maven pom.xml
file. The RouterFunction
is in the spring-boot-starter-webflux
dependency.
package com.zetcode.routes; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.web.reactive.function.server.RouterFunction; import org.springframework.web.reactive.function.server.ServerResponse; import static org.springframework.web.reactive.function.BodyInserters.fromValue; import static org.springframework.web.reactive.function.server.RequestPredicates.GET; import static org.springframework.web.reactive.function.server.RouterFunctions.route; import static org.springframework.web.reactive.function.server.ServerResponse.ok; @Configuration public class MyRoutes { @Bean RouterFunction<ServerResponse> home() { return route(GET("/"), request -> ok().body(fromValue("Home page"))); } @Bean RouterFunction<ServerResponse> about() { return route(GET("/about"), request -> ok().body(fromValue("About page"))); } }
We define two function routes.
@Bean RouterFunction<ServerResponse> home() { return route(GET("/"), request -> ok().body(fromValue("Home page"))); }
With functional routes, we can write simple and elegant code. Here we return a simple text message for the home page.
package com.zetcode.routes; 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.test.context.junit4.SpringRunner; import org.springframework.test.web.reactive.server.WebTestClient; @RunWith(SpringRunner.class) @SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT) public class MyRoutesTest { @Autowired private WebTestClient client; @Test public void test_home_page() { client.get().uri("/").exchange().expectStatus().isOk() .expectBody(String.class).isEqualTo("Home page"); } @Test public void test_about_page() { client.get().uri("/about").exchange().expectStatus().isOk() .expectBody(String.class).isEqualTo("About page"); } }
With WebTestClient
, we test the two routes.
package com.zetcode; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } }
This code sets up the Spring Boot application.
$ mvn spring-boot:run
We run the application and navigate to localhost:8080
.
In this tutorial, we have learned how to use functional routes with RouterFunction
.
List all Spring Boot tutorials.