Kotlin + Spring Boot + Spring Data JPA - CRUD example

Hello everyone, Today we will learn how to develop a Kotlin + Spring Boot CRUD web application, using Thymeleaf view, H2DB, and Spring Data JPA.


User Interface


Technologies used :

  • Spring Boot 2.3.7.RELEASE
  • Spring  5.2.12.RELEASE
  • Kotlin 2.11.3
  • Thymeleaf 5.3.0.11.RELEASE
  • Hibernate 5.4.25.Final
  • H2DB
  • Maven

After completing this tutorial what we will build? 

We will build a full-stack web application that is a basic User Management Application with CRUD features: 
  • Create User  
  • List User  
  • Update User  
  • Delete User

Project Structure



Maven[pom.xml]

A Project Object Model or POM is an XML file that contains information about the project and configuration details used by Maven to build the project.
<?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>2.3.7.RELEASE</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>
   <groupId>com.knf.dev</groupId>
   <artifactId>kotlin_springb_h2db_thymeleaf_crud</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <name>kotlin_springb_h2db_thymeleaf_crud</name>
   <description>Demo project for Spring Boot</description>

   <properties>
      <java.version>1.8</java.version>
      <kotlin.version>1.3.72</kotlin.version>
   </properties>

   <dependencies>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-data-jpa</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-thymeleaf</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-web</artifactId>
      </dependency>
      <dependency>
         <groupId>com.fasterxml.jackson.module</groupId>
         <artifactId>jackson-module-kotlin</artifactId>
      </dependency>
      <dependency>
         <groupId>org.jetbrains.kotlin</groupId>
         <artifactId>kotlin-reflect</artifactId>
      </dependency>
      <dependency>
         <groupId>org.jetbrains.kotlin</groupId>
         <artifactId>kotlin-stdlib-jdk8</artifactId>
      </dependency>
      <dependency>
         <groupId>com.h2database</groupId>
         <artifactId>h2</artifactId>
         <scope>runtime</scope>
      </dependency>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-test</artifactId>
         <scope>test</scope>
         <exclusions>
            <exclusion>
               <groupId>org.junit.vintage</groupId>
               <artifactId>junit-vintage-engine</artifactId>
            </exclusion>
         </exclusions>
      </dependency>
   </dependencies>
   <build>
      <sourceDirectory>${project.basedir}/src/main/kotlin</sourceDirectory>
<testSourceDirectory>${project.basedir}/src/test/kotlin</testSourceDirectory>
      <plugins>
         <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
         </plugin>
         <plugin>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-maven-plugin</artifactId>
            <configuration>
               <args>
                  <arg>-Xjsr305=strict</arg>
               </args>
               <compilerPlugins>
                  <plugin>spring</plugin>
                  <plugin>jpa</plugin>
               </compilerPlugins>
            </configuration>
            <dependencies>
               <dependency>
                  <groupId>org.jetbrains.kotlin</groupId>
                  <artifactId>kotlin-maven-allopen</artifactId>
                  <version>${kotlin.version}</version>
               </dependency>
               <dependency>
                  <groupId>org.jetbrains.kotlin</groupId>
                  <artifactId>kotlin-maven-noarg</artifactId>
                  <version>${kotlin.version}</version>
               </dependency>
            </dependencies>
         </plugin>
      </plugins>
   </build>
</project>



Create the User Entity

The @Entity annotation specifies that the class is an entity and is mapped to a database table. The @Id annotation specifies the primary key of an entity and the @GeneratedValue provides for the specification of generation strategies for the values of primary keys.
package com.knf.dev.entity

import javax.persistence.*

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

    @Id @GeneratedValue(strategy = GenerationType.AUTO)
    val id: Long = 0,
    val firstName: String,
    val lastName: String,
    val email: String
)



Create the User Repository

@Repository annotation is used to indicate that the class provides the mechanism for storage, retrieval, search, update and delete operation on objects.
package com.knf.dev.repository

import com.knf.dev.entity.User
import org.springframework.data.jpa.repository.JpaRepository
import org.springframework.stereotype.Repository

@Repository
interface UserRepository : JpaRepository<User, Long>



Create the User Controller 

The @RestController annotation was introduced in Spring 4.0 to simplify the engendering of RESTful web services. It's a convenience annotation that combines @Controller and @ResponseBody. @RequestMapping annotation maps HTTP requests to handler methods of MVC and REST controllers.
package com.knf.dev.controller

import com.knf.dev.entity.User
import com.knf.dev.repository.UserRepository
import org.springframework.http.HttpStatus
import org.springframework.http.MediaType
import org.springframework.http.ResponseEntity
import org.springframework.stereotype.Controller
import org.springframework.web.bind.annotation.*
import org.springframework.ui.Model
import org.springframework.web.bind.annotation.GetMapping
import java.util.*
import org.springframework.web.bind.annotation.PathVariable


@Controller
class UserController(private val userRepository: UserRepository) {

    @GetMapping("/")
    fun getAllUsers(model: Model): String? {
        val list: List<User> = userRepository.findAll()
        model.addAttribute("users", list)
        return "list-users"
    }

    @PostMapping(path = arrayOf("/createUser"))
    fun createNewUser(@ModelAttribute user: User): String {
        userRepository.save(user)
        return "redirect:/";
    }

    @GetMapping(path = ["/add"])
    fun addUserById(): String? {
        return "add-user"
    }

    @GetMapping(path = ["/edit/{id}"])
    fun editUserById(model: Model, @PathVariable("id") id: Long): String? {
        model.addAttribute("user", userRepository.findById(id))
        return "edit-user"
    }

    @PostMapping(path = ["/editUser"])
    fun editUser(@ModelAttribute user: User): String? {
        userRepository.save(user)
        return "redirect:/"
    }

    @GetMapping(path = ["/delete/{id}"])
    fun deleteUserById(@PathVariable("id") id: Long): String? {
        userRepository.deleteById(id)
        return "redirect:/"
    }
}



Spring Boot Main

The @SpringBootApplication annotation is a convenience annotation that combines the @EnableAutoConfiguration, @Configuration and the @ComponentScan annotations.
package com.knf.dev

import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication

@SpringBootApplication
class KotlinSpringbH2DBThymeleafApplication

fun main(args: Array<String>) {
    runApplication<KotlinSpringbH2DBThymeleafApplication>(*args)
}



add-user.html

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">

<head>
    <meta charset="utf-8">
    <meta http-equiv="x-ua-compatible" content="ie=edge">
    <title>Add User</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" type="text/css" media="all" href="../../
         bootstrap.min.css" th:href="@{/bootstrap.min.css}"/>
    <link rel="stylesheet" href="https://use.fontawesome.com
/releases/v5.4.1/css/all.css">
</head>

<body>
<div class="container my-5">
    <h3>Add User</h3>
    <div class="card">
        <div class="card-body">
            <div class="col-md-10">
              <form action="#" th:action="@{/createUser}" th:object="${user}"
                      method="post">
                    <div class="row">
                        <div class="form-group col-md-8">
                            <label for="firstName" class="col-form-label">
                          First Name</label>
                            <input type="text" name="firstName"
                                   class="form-control" id="firstName" 
                       placeholder="First Name"
                            />
                        </div>
                        <div class="form-group col-md-8">
                            <label for="lastName" class="col-form-label">
                           Last Name</label>
                            <input type="text" name="lastName"
                                   class="form-control" id="lastName" 
                          placeholder="Last Name"/>
                        </div>
                        <div class="form-group col-md-8">
                      <label for="email" class="col-form-label">Email</label>
                            <input type="text" name="email"
                                   class="form-control" id="email" 
                           placeholder="Email Id"/>
                        </div>
                        <div class="col-md-6">
                            <input type="submit" class="btn btn-success" 
                                  value=" Submit ">
                        </div>
                        <input type="hidden" id="id">
                    </div>
                </form>
            </div>
        </div>
    </div>
</div>
</body>
</html>



edit-user.html

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">

<head>
    <meta charset="utf-8">
    <meta http-equiv="x-ua-compatible" content="ie=edge">
    <title>Add User</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" type="text/css" media="all" href="../../
         bootstrap.min.css" th:href="@{/bootstrap.min.css}"/>
    <link rel="stylesheet" href="https://use.fontawesome.com/releases/
   v5.4.1/css/all.css">
</head>

<body>
<div class="container my-5">
    <h3>Update User</h3>
    <div class="card">
        <div class="card-body">
            <div class="col-md-10">
               <form action="#" th:action="@{/editUser}" th:object="${user}"
                      method="post">
                    <div class="row">
                        <div class="form-group col-md-8">
                            <label for="firstName" class="col-form-label">
                                    First Name</label>
                            <input type="text" th:field="*{firstName}"
                                   class="form-control" id="firstName" 
                           placeholder="First Name"
                            />
                        </div>
                        <div class="form-group col-md-8">
                            <label for="lastName" class="col-form-label">
                              Last Name</label>
                            <input type="text" th:field="*{lastName}"
                                   class="form-control" id="lastName" 
                               placeholder="Last Name"/>
                        </div>
                        <div class="form-group col-md-8">
                      <label for="email" class="col-form-label">Email</label>
                            <input type="text" th:field="*{email}"
                                   class="form-control" id="email" 
                          placeholder="Email Id"/>
                        </div>
                        <div class="col-md-6">
                            <input type="submit" class="btn btn-success" 
                       value=" Submit ">
                        </div>
                        <input type="hidden" th:field="*{id}" id="id">
                    </div>
                </form>
            </div>
        </div>
    </div>
</div>
</body>
</html>



list-users.html

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">

<head>
    <meta charset="utf-8">
    <meta http-equiv="x-ua-compatible" content="ie=edge">
    <title>All Users</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" type="text/css" media="all"
          href="../../bootstrap.min.css" th:href="@{/bootstrap.min.css}" />
    <link rel="stylesheet" href="https://use.fontawesome.com/releases
    /v5.4.1/css/all.css">
</head>

<body>
<div class="container my-2">
    <div class="card">
        <div class="card-body">
            <div th:switch="${users}" class="container my-5">
                <p class="my-5">
                    <a href="/add" class="btn btn-success">
                        <i class="fas fa-user-plus ml-2"> Add User </i></a>
                </p>
                <div class="col-md-10">
                    <h2 th:case="null">No record found !!</h2>
                    <div th:case="*">
                      <table class="table table-striped table-responsive-md">
                            <thead>
                            <tr>
                                <th>First Name</th>
                                <th>Last Name</th>
                                <th>Email</th>
                                <th>Edit</th>
                                <th>Delete</th>
                            </tr>
                            </thead>
                            <tbody>
                            <tr th:each="user : ${users}">
                                <td th:text="${user.firstName}"></td>
                                <td th:text="${user.lastName}"></td>
                                <td th:text="${user.email}"></td>
                                <td><a th:href="@{/edit/{id}(id=${user.id})}"
                                       class="btn btn-warning"> <i
                                        class="fas fa-user-edit ml-2"></i>
                                </a></td>
                              <td><a th:href="@{/delete/{id}(id=${user.id})}"
                                       class="btn btn-danger"> <i
                                        class="fas fa-user-times ml-2"></i>
                                </a></td>
                            </tr>
                            </tbody>
                        </table>
                    </div>
                </div>
            </div>
        </div>
    </div>
</div>
</body>
</html>

Download the complete source code - click here                                  

Local Setup and Run the application

Step1: Download or clone the source code from GitHub to a local machine - Click here


Step 2: mvn clean install


Step 3: Run the Spring Boot application - mvn spring-boot:run

Hit this URL in your local system, http://localhost:8080/


More ...

Kotlin + Spring Boot CRUD examples:

Kotlin + Spring Boot with Template Engines CRUD examples:

Build REST APIs with Kotlin + Spring Boot:

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