Spring Webflux Server

This post walks you through the process of creating endpoints using Spring Webflux. Please read this previous Spring Webflux Basics post before continuing with this information. We are going to use @RestController to serve data from our PersonRepository. Let’s consider the following example:

package com.jos.dem.webflux.controller;

import reactor.core.publisher.Mono;
import reactor.core.publisher.Flux;

import lombok.RequiredArgsConstructor;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import com.jos.dem.webflux.model.Person;
import com.jos.dem.webflux.repository.PersonRepository;

import lombok.extern.slf4j.Slf4j;

@Slf4j
@RestController
@RequiredArgsConstructor
public class PersonController {

    private final PersonRepository personRepository;

    @GetMapping("/persons")
    public Flux<Person> findAll() {
        log.info("Calling find persons");
        return personRepository.findAll();
    }

    @GetMapping("/persons/{nickname}")
    public Mono<Person> findById(@PathVariable String nickname) {
        log.info("Calling find person by id: {}", nickname);
        return personRepository.findById(nickname);
    }

}

The original Spring Web MVC was running on Tomcat, and the primary purpose was to run Servlet API and Servlet containers. The reactive web framework Spring WebFlux is fully non-blocking, supports Reactive Streams and runs on the Netty server. @RestController indicates that we don’t want to render views but write the results straight into the response body instead. @GetMapping tells Spring that this is the place to route person calls; it is the shorthand annotation for @RequestMapping(method=RequestMethod.GET). So, after adding this controller class to your project and running Spring Boot, you can go to: http://localhost:8080/persons

[
   {
      "nickname":"mkheck",
      "email":"mkheck@email.com"
   },
   {
      "nickname":"josdem",
      "email":"joseluis.delacruz@gmail.com"
   },
   {
      "nickname":"edzero",
      "email":"edzero@email.com"
   },
   {
      "nickname":"siedrix",
      "email":"siedrix@email.com"
   },
   {
      "nickname":"tgrip",
      "email":"tgrip@email.com"
   }
}

Here is the the endpoint to get a person by id: http://localhost:8080/persons/josdem

{
  "nickname": "josdem",
  "email": "josdem@email.com"
}

Testing The Web Layer

The best tool for testing a reactive web server is WebTestClient which is also a non-blocking, reactive client and it uses WebClient internally to perform requests and validate responses.

package com.jos.dem.webflux;

import static org.assertj.core.api.Assertions.assertThat;
import static org.springframework.http.MediaType.APPLICATION_JSON;
import static org.springframework.http.MediaType.APPLICATION_JSON_UTF8;

import lombok.extern.slf4j.Slf4j;
import lombok.RequiredArgsConstructor;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.TestInfo;
import org.junit.jupiter.api.DisplayName;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.web.reactive.server.WebTestClient;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;

import com.jos.dem.webflux.model.Person;
import com.jos.dem.webflux.controller.PersonController;

@Slf4j
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
@RequiredArgsConstructor(onConstructor_ = @Autowired)
class PersonControllerTest {

    private final WebTestClient webTestClient;

    @Test
    @DisplayName("getting all persons")
    void shouldGetPersons(TestInfo testInfo) {
        log.info("Running: {}", testInfo.getDisplayName());
        webTestClient.get().uri("/persons").accept(APPLICATION_JSON)
                .exchange()
                .expectStatus().isOk()
                .expectHeader().contentType(APPLICATION_JSON)
                .expectBodyList(Person.class);
    }

    @Test
    @DisplayName("getting person by nickname")
    void shouldGetPerson(TestInfo testInfo) {
        log.info("Running: {}", testInfo.getDisplayName());
        webTestClient.get().uri("/persons/{nickname}", "josdem").accept(APPLICATION_JSON)
                .exchange()
                .expectStatus().isOk()
                .expectHeader().contentType(APPLICATION_JSON)
                .expectBody(Person.class);
    }

}

Conclusion

Let me conclude by giving a summary:

• Spring Boot now embraces reactive programming
• Using Spring MVC-style Controllers is a good start to adopting Reactive Web
• WebFlux works well with Java functional programming
• WebFlux runs on the Netty server by default
• The best tool for testing reactive web servers is to use WebTestClient

To run the project with Gradle:

gradle bootRun

To run the project with Maven:

mvn spring-boot:run

To test the project with Gradle:

gradle test

To test the project with Maven:

mvn test

To browse the project go here, to download the project:

git clone https://github.com/josdem/reactive-webflux-workshop.git
cd server

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