Spring Boot - Testing Spring WebFlux Controller with @WebFluxTest - Example

In this section, we will learn how to test Spring WebFlux Controller with @WebFluxTest.


1. @WebFluxTest

Instead of bootstrapping the entire application context for every test, @WebFluxTest allows us to initialize only the parts of the Application context that are necessary for our Spring WebFlux layer. This allows us to focus on testing the controllers, and related components.

Following beans will be scanned while using @WebFluxTest:

  • @Controller
  • @ControllerAdvice
  • @JsonComponent
  • Converter
  • GenericConverter
  • Filter
  • WebFluxConfigurer

Regular @Component, @Service or @Repository beans are not scanned when using this annotation.

This approach not only speeds up the testing process but also ensures a focused and efficient testing environment. 

This approach is also known as "slicing" the application context.

The annotation can be used to test a single controller by passing it as an attribute, for example @WebFluxTest(SomeController.class).

@WebFluxTest(StudentController.class)
public class StudentControllerTest {

    @Autowired
    private WebTestClient webTestClient;

    @MockBean
    private StudentService studentService;

    //Unit test Save Student REST API
    @Test
    void shouldCreateStudent() throws Exception {

          //todo...       
    }
}

  • We use @MockBean in Spring Boot when we want to mock an object that is present in the Spring application context.@MockBean takes care of replacing the bean with what we want to simulate in our test.
  • WebTestClient supports execution of tests against Spring WebFlux server endpoints. WebTestClient uses simulated requests and responses to avoid exhausting server resources and can bind directly to the WebFlux server infrastructure. WebTestClient is similar to MockMvc. The only difference between those test web clients is that WebTestClient is aimed at testing WebFlux endpoints.

2. Creating a spring boot application

First, open the Spring initializr https://start.spring.io

Then, Provide the Group and Artifact name. We have provided Group name com.knf.dev.demo and Artifact webflux-example. Here I selected the Maven project - language Java 17 - Spring Boot 3.1.5 , Spring Reactive Web, Spring Data R2DBC, and H2 Database.

Then, click on the Generate button. When we click on the Generate button, it starts packing the project in a .zip(webfluxtest-example) file and downloads the project. Then, Extract the Zip file. 

Then, import the project on your favourite IDE.

Final Project Directory:



Complete pom.xml

<?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 
   https://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>3.1.5</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>
   <groupId>com.knf.dev.demo</groupId>
   <artifactId>webfluxtest-example</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <name>webfluxtest-example</name>
   <description>Demo project for Spring Boot</description>
   <properties>
      <java.version>17</java.version>
   </properties>
   <dependencies>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-data-r2dbc</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-webflux</artifactId>
      </dependency>

      <dependency>
         <groupId>com.h2database</groupId>
         <artifactId>h2</artifactId>
         <scope>runtime</scope>
      </dependency>
      <dependency>
         <groupId>io.r2dbc</groupId>
         <artifactId>r2dbc-h2</artifactId>
         <scope>runtime</scope>
      </dependency>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-test</artifactId>
         <scope>test</scope>
      </dependency>
      <dependency>
         <groupId>io.projectreactor</groupId>
         <artifactId>reactor-test</artifactId>
         <scope>test</scope>
      </dependency>
   </dependencies>

   <build>
      <plugins>
         <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <configuration>
               <image>
                  <builder>paketobuildpacks/builder-jammy-base:latest</builder>
               </image>
            </configuration>
         </plugin>
      </plugins>
   </build>

</project>

spring-boot-starter-test starter will provide following libraries:

  • JUnit 
  • Spring Test & Spring Boot Test 
  • AssertJ
  • Hamcrest 
  • Mockito 
  • JSONassert 
  • JsonPath 


Create schema.sql

CREATE TABLE IF NOT EXISTS students
(id INT NOT NULL AUTO_INCREMENT,
name VARCHAR(255),
email VARCHAR(255),
PRIMARY KEY (id));


Create Student Entity Class

package com.knf.dev.demo.entity;

import org.springframework.data.relational.core.mapping.Table;
import org.springframework.data.annotation.Id;

@Table("students")
public class Student {

    @Id
    private Integer id;
    private String name;
    private String email;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public Student(String name, String email) {
        this.name = name;
        this.email = email;
    }

    public Student() {
    }

    public Student(Integer id, String name, String email) {
        this.id = id;
        this.name = name;
        this.email = email;
    }
}


Create Student Repository

package com.knf.dev.demo.repository;

import com.knf.dev.demo.entity.Student;
import org.springframework.data.repository.reactive.ReactiveCrudRepository;

public interface StudentRepository extends ReactiveCrudRepository<Student, Integer> {
}


Create Student Service

package com.knf.dev.demo.service;

import com.knf.dev.demo.entity.Student;
import com.knf.dev.demo.repository.StudentRepository;
import org.springframework.stereotype.Service;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

@Service
public class StudentService {

    private final StudentRepository studentRepository;

    public StudentService(StudentRepository studentRepository) {
        this.studentRepository = studentRepository;
    }

    public Flux<Student> getAllStudents(){

        return this.studentRepository.findAll();
    }

    public Mono<Student> getStudentById(int id){

        return this.studentRepository.findById(id);
    }

    public Mono<Student> createStudent(final Student student){

        return this.studentRepository.save(student);
    }

    public Mono<Student> updateStudent(int id, final Mono<Student> studentMono){

        return this.studentRepository.findById(id)
                .flatMap(p -> studentMono.map(u -> {
                    p.setEmail(u.getEmail());
                    p.setName(u.getName());
                    return p;
                }))
                .flatMap(p -> this.studentRepository.save(p));
    }

    public Mono<Void> deleteStudent(final int id){
        return this.studentRepository.deleteById(id);
    }
}


Create Student Controller

package com.knf.dev.demo.controller;

import com.knf.dev.demo.entity.Student;
import com.knf.dev.demo.service.StudentService;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

@RestController
@RequestMapping("/api/v1")
public class StudentController {

    private final StudentService studentService;

    public StudentController(StudentService studentService) {
        this.studentService = studentService;
    }

    @GetMapping("/students")
    public Flux<Student> getAllStudents(){

        return this.studentService.getAllStudents();
    }

    @GetMapping("/students/{id}")
    public Mono<ResponseEntity<Student>> getStudentById(@PathVariable int id){

        return this.studentService.getStudentById(id)
                .map(ResponseEntity::ok)
                .defaultIfEmpty(ResponseEntity.notFound().build());
    }

    @PostMapping("/students")
    public Mono<Student> createStudent(@RequestBody Mono<Student> studentMono){

        return studentMono.flatMap(this.studentService::createStudent);
    }

    @PutMapping("/students/{id}")
    public Mono<Student> updateStudent(@PathVariable int id,
                                        @RequestBody Mono<Student> studentMono){
        return this.studentService.updateStudent(id, studentMono);
    }

    @DeleteMapping("/students/{id}")
    public Mono<Void> deleteStudent(@PathVariable int id){

        return this.studentService.deleteStudent(id);
    }

}


WebfluxtestExampleApplication class

package com.knf.dev.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class WebfluxtestExampleApplication {

   public static void main(String[] args) {
      SpringApplication.run(WebfluxtestExampleApplication.class, args);
   }

}


Write Unit test for StudentController

Let’s write our test cases by creating StudentControllerTest class

Create StudentControllerTest

When using JUnit 4, this annotation should be used in combination with @RunWith(SpringRunner.class). But for this example  we are using JUnit 5, there’s no need to add the equivalent @ExtendWith(SpringExtension.class).
package com.knf.dev.demo;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

import com.knf.dev.demo.controller.StudentController;
import com.knf.dev.demo.entity.Student;
import com.knf.dev.demo.service.StudentService;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.reactive.WebFluxTest;
import org.springframework.boot.test.mock.mockito.MockBean;
import org.springframework.http.MediaType;
import org.springframework.test.web.reactive.server.WebTestClient;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import static org.mockito.ArgumentMatchers.any;
import static org.mockito.BDDMockito.given;

@WebFluxTest(StudentController.class)
public class StudentControllerTest {

    @Autowired
    private WebTestClient webTestClient;

    @MockBean
    private StudentService studentService;

    //Unit test Save Student REST API
    @Test
    void shouldCreateStudent() throws Exception {

        // Setup
        Student student = new Student(1,"Alpha","alpha@tmail.com");

        given(studentService.createStudent(any(Student.class)))
                .willReturn(Mono.just(student));

        // Action that we are going test
        WebTestClient.ResponseSpec response = webTestClient.post()
                .uri("/api/v1/students")
                .contentType(MediaType.APPLICATION_JSON)
                .accept(MediaType.APPLICATION_JSON)
                .body(Mono.just(student), Student.class)
                .exchange();

        // Verify the result using assert statements
        response.expectStatus().is2xxSuccessful()
                .expectBody()
                .consumeWith(System.out::println)
                .jsonPath("$.name").isEqualTo(student.getName())
                .jsonPath("$.email").isEqualTo(student.getEmail());
    }

    // Unit test Get Student by Id REST API
    @Test
    public void shouldReturnStudent() {

        // Setup
        Integer id = 1;
        Student student = new Student("Alpha","alpha@tmail.com");

        given(studentService.getStudentById(id)).willReturn(Mono.just(student));

        // Action that we are going test
        WebTestClient.ResponseSpec response = webTestClient.get()
                .uri("/api/v1/students/{id}", Collections.singletonMap("id", id))
                .exchange();

        // Verify the result using assert statements
        response.expectStatus().isOk()
                .expectBody()
                .consumeWith(System.out::println)
                .jsonPath("$.name").isEqualTo(student.getName())
                .jsonPath("$.email").isEqualTo(student.getEmail());
    }

    // Unit test Get All Student REST API
    @Test
    public void shouldReturnListOfStudents() {

        // Setup
        List<Student> students = new ArrayList<>(
                Arrays.asList(new Student(1, "Alpha", "alpha@tmail.com"),
                        new Student(2, "Beta", "beta@tmail.com"),
                        new Student(3, "Gama", "gama@tmail.com")));
        Flux<Student> studentFlux = Flux.fromIterable(students);
        given(studentService.getAllStudents()).willReturn(studentFlux);

        // Action that we are going test
        WebTestClient.ResponseSpec response = webTestClient.get().uri("/api/v1/students")
                .accept(MediaType.APPLICATION_JSON)
                .exchange();

        // Verify the result using assert statements
        response.expectStatus().isOk()
                .expectHeader().contentType(MediaType.APPLICATION_JSON)
                .expectBodyList(Student.class)
                .consumeWith(System.out::println);
    }

    @Test
    public void shouldUpdateStudent() throws Exception {

        // Setup
        Integer id = 1;
        Student student = new Student("Alpha","alpha@tmail.com");

        // Action that we are going test
        given(studentService.updateStudent(any(Integer.class),any(Mono.class)))
                .willReturn(Mono.just(student));

        WebTestClient.ResponseSpec response = webTestClient.put()
                .uri("/api/v1/students/{id}", Collections.singletonMap("id", id))
                .contentType(MediaType.APPLICATION_JSON)
                .accept(MediaType.APPLICATION_JSON)
                .body(Mono.just(student), Student.class)
                .exchange();

        // Verify the result using assert statements
        response.expectStatus().isOk()
                .expectHeader().contentType(MediaType.APPLICATION_JSON)
                .expectBody()
                .consumeWith(System.out::println)
                .jsonPath("$.name").isEqualTo(student.getName())
                .jsonPath("$.email").isEqualTo(student.getEmail());
    }

    // Unit Test Delete Student REST API
    @Test
    public void shouldDeleteStudent() {

        // Setup
        Integer id = 1;
        Mono<Void> voidReturn  = Mono.empty();
        given(studentService.deleteStudent(id)).willReturn(voidReturn);

        // Action that we are going test
        WebTestClient.ResponseSpec response = webTestClient.delete()
                .uri("/api/v1/students/{id}", Collections.singletonMap("id",  id))
                .exchange();

        // Verify the result using assert statements
        response.expectStatus().is2xxSuccessful()
                .expectBody()
                .consumeWith(System.out::println);
    }
}

  • We use @MockBean in Spring Boot when we want to mock an object that is present in the Spring application context.@MockBean takes care of replacing the bean with what we want to simulate in our test.
  • WebTestClient supports execution of tests against Spring WebFlux server endpoints. WebTestClient uses simulated requests and responses to avoid exhausting server resources and can bind directly to the WebFlux server infrastructure. WebTestClient is similar to MockMvc. The only difference between those test web clients is that WebTestClient is aimed at testing WebFlux endpoints.


3. Run the test

Or you can run the test using following command: 

mvn test -Dtest=StudentControllerTest

Download the source code - click here!

Popular posts from this blog

Learn Java 8 streams with an example - print odd/even numbers from Array and List

Example 1: Java 8 program to print odd numbers from a List   import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; /*Java 8 Program to find Odd Numbers from a List*/ public class DriverClass { public static void main( String [] args) { List < Integer > numbers = Arrays. asList( 1 , 4 , 8 , 40 , 11 , 22 , 33 , 99 ); List < Integer > oddNumbers = numbers.stream(). filter(o -> o % 2 != 0 ). collect(Collectors.toList()); System.out.println(oddNumbers); } } 1. Initialize List using Arrays.asList() method. Java's built-in Arrays.asList() method converts an array into a list. This method takes an array as an argument and returns a List object. 2.  Java List interface provides stream() method which returns a sequential Stream with list of Integer as its source. 3. The Java stream filter() method allow
Read more

Java Stream API - How to convert List of objects to another List of objects using Java streams?

Image
In this section, we will show you how to convert a List of objects to another List of objects in Java using the Java streams map(). The ‘map’ method maps each element to its corresponding result. Java Stream API   The Java Stream API provides a functional programming approach over the object oriented capabilities of Java. It is used for processing collections of objects. The Stream in Java can be defined as a sequence of elements from a source List, Set or Array. Most of the stream operations return a Stream. This avails engender a chain of stream operations(stream pipe-lining). The streams withal support the aggregate or terminal operations on the elements. for example, finding the sum or maximum element or finding the average etc...Stream operations can either be executed sequentially or parallel. when performed parallelly, it is called a parallel stream.   Stream map() Method   The Java 8 Stream map() is an intermediate operation. It converts Stream<obj1> to Stream<obj2>
Read more

Registration and Login with Spring Boot + Spring Security + Thymeleaf

Image
In this section, we will learn how to create user registration and login using Spring boot, Spring security, Thymeleaf, JPA, and H2DB. The GitHub repository link is provided at the end of this tutorial. You can download the source code. Technologies used: Spring Boot 2.5.5  Spring Data JPA  Spring Security  Thymeleaf  Maven 3+  Java 17  H2 Database   User Interface User Registration Authentication Failed Authentication success Sign out Final Project Structure: Complete pom.xml: <? 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 https://maven.apache.org/xsd/maven-4.0.0.xsd" > < modelVersion >4.0.0</ modelVersion > < parent > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-starter-pare
Read more

Java, Spring Boot Mini Project - Library Management System - Download

Image
Hello everyone, Hope you are doing well. Here, we provide a Library Management System mini-project for beginners, it's free for download. Maybe you can build more on top of this project and create your own product, that's all about you. The source code download link is provided at the end of this post. 1. Benefit of this project You could cover the following technologies and features by learning and debugging this mini project. Java 17 Java Stream Java Lamda Expressions Java Records Functional programming Object-oriented programming var Keyword in Java Generics in Java Java Switch Spring boot 2.6.4 Spring Security Thymeleaf template engine OpenCSV Spring Data JPA Server Side Pagination H2 Database  Bootstrap HTML CSS and more... 2. Objective Of Spring Boot On Library Management System The main objective of this project is to manage the details of the books, author, category, and publisher. Only Admin/Librarian will manage all these activities. Also, they can export the data in
Read more

ReactJS, Spring Boot JWT Authentication Example

Image
In this tutorial, we’ll create a user registration & login example using ReactJS, Spring Boot, Spring Security, and JWT authentication. You could download the source code from our Github repository, the download link is provided at the end of this tutorial. Technologies used Backend Technologies: Java 17 Spring Boot 2.7.0 Spring Security Spring Data JPA JWT H2 Database Frontend Technologies: React 17.0.1 Axios 0.27.2 Redux 4.0.5 Bootstrap 4.5.2 ReactJS - SpringBoot - JWT - Flow Backend Project Directory: Frontend Project Directory: Following is the screenshot of our application - User Registration: User Signin: Profile View: Access Resource: We will build two projects:  1. Backend:   spring-boot-security-jwt 2. Frontend: react-redux-jwt Project 1: spring-boot-security-jwt Pom.xml <?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"
Read more

Spring Boot + Mockito simple application with 100% code coverage

Image
In this article, we will show you a simple  Spring Boot example to demonstrate test methods for Controllers, Service, and Repository, And code coverage analysis using the EclEmma plugin. Technologies used: Spring Boot 2.6.4 Mockito 3.11.2 Maven 3+ EclEmma plugin Junit 5 Java 17 A quick overview of  Spring Boot, Mockito, and EclEmma plugin Spring boot: Spring boot to develop REST web services and microservices. Spring Boot has taken the Spring framework to the next level. It has drastically reduced the configuration and setup time required for spring projects. We can set up a project with almost zero configuration and start building the things that actually matter to your application. Mockito: Mockito is a mocking framework, a JAVA-predicated library that is utilized for efficacious unit testing of JAVA applications. Mockito is utilized to mock interfaces so that a dummy functionality can be integrated into a mock interface that can be utilized in unit testing. EclEmma : E
Read more

Top 5 Java ORM tools - 2024

Image
  The term ORM refers to object-relational mapping, which uses objects to adapt programming languages to database systems while allowing them to function with SQL and object-oriented programming ideas. Any kind of database management system that can accomplish object mapping to the table in the virtual system is suitable for the implementation of ORM. Java has a wide variety of ORM tools, some of which are mentioned below: 1. Hibernate Hibernate is a lightweight, open-source, non-invasive Java ORM (Object-Relational Mapping) framework that allows developers to create objects that function independently of database software and create persistence logic in any Java or JavaEE application. It offers an abstraction layer, so developers don't have to bother about implementations; Hibernate handles these tasks internally, such as connecting to databases and creating queries to carry out CRUD operations, among other things. Persistence logic development is done with it. Persistence logic r
Read more

Java - Blowfish Encryption and decryption Example

Image
Blowfish is an encryption method developed by Bruce Schneier in 1993 as an alternative to the DES encryption method. It is significantly faster than DES and provides good encryption speed, although no effective cryptanalysis technique has been found to date. It is one of the first secure block ciphers that is not protected by any patents and is therefore freely available for anyone to use. This is a symmetric block cipher algorithm. Block size: 64 bits Key size: variable size from 32 to 448 bits number of subsections: 18 [P-array] number of rounds: 16 number of substitution blocks: 4 [each with 512 records of 32 bits each] develop  Example 1: Encryption and decryption using Blowfish import java.io.UnsupportedEncodingException; import java.nio.charset.Charset; import java.security.InvalidKeyException; import java.security.NoSuchAlgorithmException; import java.util.Base64; import javax.crypto.BadPaddingException; import javax.crypto.Cipher; import javax.crypto.IllegalBlockSizeExc
Read more

Spring boot video streaming example-HTML5

Image
Hello everyone, Today we will learn how to stream MP4 video using Spring Boot and Spring Web Flux.  The Source code download link is provided at the end of this post. New, Quarkus Practice User Interface   Project Structure: G radle(build.gradle) plugins { id 'org.springframework.boot' version '2.5.4' id 'io.spring.dependency-management' version '1.0.11.RELEASE' id 'java' } group = 'com.knf.demo' version = '0.0.1-SNAPSHOT' sourceCompatibility = '11' repositories { mavenCentral() } dependencies { implementation 'org.springframework.boot:spring-boot-starter-webflux' testImplementation 'org.springframework.boot:spring-boot-starter-test' testImplementation 'io.projectreactor:reactor-test' } test { useJUnitPlatform() } Service (VideoStreamingService.java) package  com.knf.demo.service ; import org.springframework.beans.factory.annotation. Autowired ; import org.springframew
Read more

Google Cloud Storage + Spring Boot - File Upload, Download, and Delete

Image
In this section, we will learn  how to  create a simple spring boot application to perform different file operations such as upload, download, list, and delete files from the Google Cloud Storage. 1.  A little bit of Background Google Cloud Storage Cloud Storage is a managed service for storing unstructured data. Store any amount of data and retrieve it as often as you like. More Info - click here! Spring Boot Spring Boot makes it easy to create stand-alone, production-grade Spring-based Applications that you can "just run".  More Info - click here! 2. Create a GCP Project First, Sign into the Google console at  https://console.cloud.google.com . You can create a new project by first selecting the project dropdown in the top left and selecting " New Project ". Next, specify your GCP  Project name  and  Project ID . Then  Click on the " CREATE " button. Copy " Project ID " and keep it for future purposes. 3. Create a Google Cloud Storage bucket Fr
Read more