Web development with Kotlin and Spring is a great way to build modern web applications. Kotlin is a statically typed programming language that runs on the Java Virtual Machine and can be used to develop both server-side and client-side applications. Spring is a popular Java application framework that makes it easy to create web applications.
In this post, we'll take a look at how to use Kotlin and Spring to build web applications. We'll start by looking at some of the benefits of using Kotlin for web development. We'll then look at how to set up a Kotlin and Spring development environment. Finally, we'll walk through a simple example web application that uses Kotlin and Spring.
There are many reasons to consider using Kotlin for web development. Kotlin is a concise and expressive programming language that can help you write less code and get more done. Kotlin is also interoperable with Java, meaning that you can use existing Java libraries in Kotlin code. Kotlin is also backed by JetBrains, the company behind the popular IntelliJ IDEA Java IDE, so you can be confident that Kotlin will continue to be developed and supported.
Before we can start developing web applications with Kotlin and Spring, we need to set up a development environment. We'll need to install the Kotlin compiler and runtime, as well as a Java development kit (JDK). We'll also need to install the Spring Framework.
There are a few different ways to install Kotlin. We can download a Kotlin compiler from the Kotlin website or we can use a build tool such as Gradle or Maven. We'll use Gradle in this example.
First, we need to create a file called build.gradle
in the root directory of our project. We'll add the following lines to the file:
plugins {
id 'org.jetbrains.kotlin.jvm' version '1.3.72'
}
repositories {
jcenter()
}
dependencies {
implementation 'org.jetbrains.kotlin:kotlin-stdlib-jdk8'
implementation 'org.springframework.boot:spring-boot-starter-webflux'
}
This file tells Gradle to download the Kotlin compiler and runtime, as well as the Spring Framework.
Next, we need to create a file called settings.gradle
in the root directory of our project. We'll add the following line to the file:
include ':kotlin-web-example'
This file tells Gradle to include our project in the build.
Finally, we need to create a file called kotlin-web-example.gradle
in the root directory of our project. We'll add the following lines to the file:
group 'com.example'
version '0.0.1-SNAPSHOT'
apply plugin: 'org.jetbrains.kotlin.jvm'
repositories {
jcenter()
}
dependencies {
implementation 'org.jetbrains.kotlin:kotlin-stdlib-jdk8'
implementation 'org.springframework.boot:spring-boot-starter-webflux'
}
This file tells Gradle the group and version of our project, as well as the dependencies we need.
Now that we have our build files set up, we can run the gradle build
command to build our project. This will download the Kotlin compiler and runtime, as well as the Spring Framework.
Now that we have our development environment set up, we're ready to write some code. We'll start by creating a file called HelloController.kt
in the src/main/kotlin
directory of our project. We'll add the following lines of code to the file:
package com.example.helloworld
import org.springframework.web.bind.annotation.GetMapping
import org.springframework.web.bind.annotation.RestController
@RestController
class HelloController {
@GetMapping("/hello")
fun hello(): String {
return "Hello, world!"
}
}
This code defines a simple HelloController
class that has a hello
method. This method is annotated with the @GetMapping
annotation, which tells Spring that this method should be called when a GET
request is made to the /hello
path. The @RestController
annotation tells Spring that this class is a controller that handles web requests.
Next, we need to create a file called Application.kt
in the src/main/kotlin
directory of our project. We'll add the following lines of code to the file:
package com.example.helloworld
import org.springframework.boot.SpringApplication
import org.springframework.boot.autoconfigure.SpringBootApplication
@SpringBootApplication
class Application
fun main(args: Array<String>) {
SpringApplication.run(Application::class.java, *args)
}
This code defines a simple Application
class that is annotated with the @SpringBootApplication
annotation. This annotation tells Spring that this is a Spring Boot application. The main
method is the entry point for our application. This method calls the SpringApplication.run
method, which starts our application.
Now that we have our code written, we can run the gradle build
command to build our project. This will compile our Kotlin code and package it into a JAR file.
We can then run the java -jar build/libs/kotlin-web-example-0.0.1-SNAPSHOT.jar
command to start our application. We can then access our application at http://localhost:8080/hello.
In this post, we've looked at how to use Kotlin and Spring to build web applications. We've seen how Kotlin can help us write less code and how Spring makes it easy to create web applications. We've also seen how to set up a Kotlin and Spring development environment and how to write a simple web application.