Implement enterprise-level applications using Spring Boot and Kotlin language

As the demand for enterprise-level applications continues to increase, various new technologies are emerging in endlessly. However, with the development of Java technology, more and more developers are beginning to pay attention to the Kotlin language. Kotlin is a statically typed programming language developed by JetBrains. It provides simpler, safer, easier to read and write code for JVM-based applications, and therefore reflects greater productivity in development.

At the same time, Spring Boot has become the preferred framework for enterprise-level applications because of its lightweight, fast construction, and simple configurability. This article will introduce how to use Spring Boot and Kotlin language to implement enterprise-level applications.

1. Project construction and configuration

Spring Boot provides a Spring Initializr tool that can quickly configure the required dependencies and configuration files. As an emerging programming language, Kotlin language is also supported in this tool.

In order to build the project, you need to download JDK 1.8 or above first, and you also need to install an IDE tool. It is recommended to use IntelliJ IDEA.

1.1 New Project

Open IntelliJ IDEA, select File -> New -> Project in the main menu, then select Spring Initializr in the pop-up dialog box, and fill in the basic information of the project (such as project name, description, etc.), click Next.

In the Spring Initializr configuration, select Kotlin as the main programming language, and add the required dependencies for Web, JPA, MySQL, etc., as shown in the following figure:

Click Next to configure the project name, location and other information. During this process, make sure Gradle is used as the build tool and Java SDK 8.0 or higher is used.

Click Finish, IntelliJ IDEA will automatically generate a project named "spring-kotlin-demo".

1.2 Project configuration

In order to build the project into a deployable Jar package or War package, you need to modify the project configuration file build.gradle:

//build. gradle file
plugins {

kotlin("jvm") version "1.4.30"
id("org.springframework.boot") version "2.4.3"
kotlin("plugin.spring") version "1.4.30"

}

group = "com.example"
version = "0.0.1-SNAPSHOT"
java.sourceCompatibility = JavaVersion.VERSION_1_8

repositories {

mavenCentral()

}

dependencies {

implementation("org.springframework.boot:spring-boot-starter-data-jpa")
implementation("org.springframework.boot:spring-boot-starter-web")
implementation("com.fasterxml.jackson.module:jackson-module-kotlin")
implementation("mysql:mysql-connector-java")
testImplementation("org.springframework.boot:spring-boot-starter-test")

}

The build.gradle file includes the following modifications:
– The Kotlin language plugin is added
– Java version is targeted to 1.8
– The necessary dependencies are added for building Spring Boot application for JPA, Web, and MySQL.
– The Jackson module for Kotlin and MySQL connector.

2. Implementation of business requirements

In Spring Boot, using the Kotlin language to implement business requirements does not require special skills, and is similar to the Java language. Here, we illustrate its specific usage with a simple use case.

2.1 Create a data model

In Kotlin, defining entity classes is similar to that in Java. When defining a specific class, you need to use the data class keyword. This is a way of defining data classes provided in the Kotlin language:

//UserModel.kt

package com.example.demo .model

import javax.persistence.*

@Entity
@Table(name = "user")
data class UserModel(

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
val id: Long? = null,

val name: String,
val age: Int

)

In the above code, use @Entity and @Table annotations to specify the data table name and specify that the class is a JPA entity class. Each entity class must specify a primary key, annotated with @Id annotation. Unlike Java, a data class is defined using the data keyword.

2.2 Implementing the data access layer

To implement the data access layer, you need to use Spring Data JPA, which is a tool provided by the Spring framework to access the database. Spring Data JPA can help developers read and transfer data from the database without writing cumbersome SQL statements.

//UserRepository.kt

package com.example.demo.repository

import com.example.demo.model.UserModel
import org.springframework.data .repository.CrudRepository
import org.springframework.stereotype.Repository

@Repository
interface UserRepository : CrudRepository {

fun findByName(name: String): Iterable<UserModel>

}

In the above code, a UserRepository interface is defined, which uses CrudRepository to implement common add, delete, modify and query operations. Also defined is a method for finding users by name.

2.3 Implementing the control layer

In Spring Boot, using Kotlin to implement the controller is similar to Java. You can use annotation to build the controller:

//UserController. kt

package com.example.demo.controller

import com.example.demo.model.UserModel
import com.example.demo.repository.UserRepository
import org. springframework.beans.factory.annotation.Autowired
import org.springframework.web.bind.annotation.*

@RestController
@RequestMapping("/user")
class UserController {

@Autowired
lateinit var userRepository: UserRepository

@GetMapping("/findAll")
fun findAll() = userRepository.findAll()

@GetMapping("/findByName/{name}")
fun findByName(@PathVariable("name") name: String) = userRepository.findByName(name)

@PostMapping("/save")
fun saveUser(@RequestBody userModel: UserModel) = userRepository.save(userModel)

@PutMapping("/update")
fun updateUser(@RequestBody userModel: UserModel) = userRepository.save(userModel)

@DeleteMapping("/delete/{id}")
fun deleteUser(@PathVariable("id") id: Long) = userRepository.deleteById(id)

}

In the above code, a UserController controller class is defined, which uses the @Autowired annotation to automatically assemble userRepository. At the same time, the method of adding, deleting, modifying and checking users is also defined.

3. Run and test

In the root directory of the project, run the command gradle bootRun to start the Spring Boot application, and you can call the API interface through localhost:8080/user/findAll for testing. While using the Kotlin language, you can also see output results similar to Java.

To sum up, using Spring Boot and Kotlin language to implement enterprise-level applications can make development work simpler, safer and more productive. However, it must be noted that the cost of learning the Kotlin language is relatively high, so more practice and thinking are required during the actual development process.

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