Spring Webflux Client

We covered the reactive web server in the previous Spring Boot Server; this time, we will see the client side. Let’s start creating a new project with Webflux and Lombok as dependencies:

spring init --dependencies=webflux,lombok --build=gradle --type=gradle-project --language=java client

Here is the complete build.gradle file generated:

plugins {
  id 'java'
  id 'org.springframework.boot' version '3.0.6'
  id 'io.spring.dependency-management' version '1.1.0'
}

group = 'com.jos.dem.webflux'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 17

configurations {
  compileOnly {
    extendsFrom annotationProcessor
  }
}

repositories {
  mavenCentral()
}

dependencies {
  implementation('org.springframework.boot:spring-boot-starter-webflux')
  compileOnly 'org.projectlombok:lombok'
  annotationProcessor 'org.projectlombok:lombok'
  implementation('org.springframework.boot:spring-boot-starter-data-mongodb-reactive')
  testImplementation 'org.springframework.boot:spring-boot-starter-test'
  testImplementation 'io.projectreactor:reactor-test'
}

tasks.named('test') {
  useJUnitPlatform()
}

Now let’s create a simple DTO to retrieve information from our reactive server.

package com.jos.dem.webflux.model;

import lombok.Data;

@Data
public class Person {

  private String nickname;
  private String email;

}

Lombok is a great tool to avoid boilerplate code, for knowing more please go here. Next, we are going to use CommandLineRunner to start our workflow. The CommandLineRunner is a callback interface in Spring Boot, when Spring Boot starts will call it and pass in args through a run() internal method.

package com.jos.dem.webflux;

import com.jos.dem.webflux.model.Person;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.web.reactive.function.client.WebClient;

@Slf4j
@SpringBootApplication
public class PersonApplication {

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

    @Bean
    WebClient webClient() {
        return WebClient.create("http://localhost:8080");
    }

    @Bean
    CommandLineRunner run(WebClient client) {
        return args -> {
            client.get().uri("/persons").retrieve()
                    .bodyToFlux(Person.class)
                    .subscribe(person -> log.info("person: {}", person));
        };
    }

}

WebClient defined as @Bean is a non-blocking, reactive client for performing HTTP requests with our reactive web server, and again Netty is used by default. Do not forget to run this client in a different port using the following specification in our application.properties file.

server.port=8081

To run the project:

gradle bootRun

Using Maven

You can do the same using Maven, the only difference is that you need to specify --build=maven parameter in the spring init command line:

spring init --dependencies=webflux,lombok --build=maven --language=java client

This is the pom.xml file generated:

<?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.jos.dem.webflux</groupId>
  <artifactId>reactive-webflux-workshop</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>demo</name>
  <description>Demo project for Spring Webflux</description>

  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>3.0.6</version>
    <relativePath/> <!-- lookup parent from repository -->
  </parent>

  <properties>
    <java.version>17</java.version>
  </properties>

  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-webflux</artifactId>
    </dependency>
    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <optional>true</optional>
    </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>
          <excludes>
            <exclude>
              <groupId>org.projectlombok</groupId>
              <artifactId>lombok</artifactId>
            </exclude>
          </excludes>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

To run the project with Maven:

mvn spring-boot:run

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

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

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