Angular 12 Kotlin SpringBoot MySQL CRUD Example

In this tutorial, we show you Angular 12 Http Client & Spring Boot Server example that uses Spring JPA to do CRUD with MySQL and Angular 12 as a front-end technology to make request and receive response.

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Related pages:

I. Technologies

– Java 1.8
– Maven 3.3.9
– Spring Tool Suite – Version 3.8.4.RELEASE
– Spring Boot: 2.0.3.RELEASE
– Angular 12
– RxJS 6

II. Overview

kotlin-spring-boot-angular-6-crud-httpclient-spring-rest-api-data-mysql-crud-spring-jpa + angular-http-service-architecture

1. Spring Boot Server

kotlin-spring-boot-angular-6-crud-httpclient-spring-rest-api-data-mysql-crud-spring-jpa + spring-server-architecture

2. Angular 12 Client

kotlin-spring-boot-angular-6-crud-httpclient-spring-rest-api-data-mysql-crud-spring-jpa + angular-client-architecture

III. Practice

1. Project Structure

1.1 Spring Boot Server

Angular-6-Crud-HttpClient-Kotlin-SpringBoot-MySQL-CRUD-Spring-JPA +Kotlin-SpringBoot-project

Customer class corresponds to entity and table customer.
CustomerRepository is an interface extends CrudRepository, will be autowired in CustomerController for implementing repository methods and custom finder methods.
CustomerController is a REST Controller which has request mapping methods for RESTful requests such as: getAllCustomers, postCustomer, deleteCustomer, deleteAllCustomers, findByAge, updateCustomer.
– Configuration for Spring Datasource and Spring JPA properties in
Dependencies for Spring Boot and MySQL in pom.xml

1.2 Angular 12 Client

kotlin-spring-boot-angular-6-crud-httpclient-spring-rest-api-data-mysql-crud-spring-jpa + angular-client-structure

In this example, we focus on:
– 4 components: customers-list, customer-details, create-customer, search-customer.
– 3 modules: FormsModule, HttpClientModule, AppRoutingModule.
customer.ts: class Customer (id, firstName, lastName)
customer.service.ts: Service for Http Client methods

2. How to do

2.1 Spring Boot Server

2.1.1 Dependency


2.1.2 Customer – Data Model


package com.ozenero.springrest.mysql.model

import javax.persistence.Entity
import javax.persistence.Id
import javax.persistence.GeneratedValue
import javax.persistence.GenerationType
class Customer(
		var name: String,
		var age: Int,
		var active: Boolean = false,
		@Id @GeneratedValue(strategy = GenerationType.AUTO)
		val id: Long = -1) {
	private constructor() : this("", -1)
	override fun toString(): String{
		return "Customer [id= + ${} + , name= + ${} + , age= + ${this.age} + , active= + ${} + ]";
2.1.3 JPA Repository


package com.ozenero.springrest.mysql.repo

import org.springframework.stereotype.Repository;

import com.ozenero.springrest.mysql.model.Customer;

interface CustomerRepository : CrudRepository {
	fun findByAge(age: Int): Iterable
2.1.4 REST Controller


package com.ozenero.springrest.mysql.controller

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.CrossOrigin;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import com.ozenero.springrest.mysql.repo.CustomerRepository
import com.ozenero.springrest.mysql.model.Customer

@CrossOrigin(origins = arrayOf("http://localhost:4200"))
class CustomerController {
	lateinit var repository: CustomerRepository
	fun findAll() = repository.findAll()
	fun postCustomer(@RequestBody customer: Customer): Customer{
		return Customer(, customer.age));
	fun deleteCustomer(@PathVariable("id") id: Long): ResponseEntity{
		println("Delete Customer with ID = " + id + "...");
		return ResponseEntity("Customer has been deleted!", HttpStatus.OK);
	fun deleteAllCustomers(): ResponseEntity{
		println("Delete All Customers...");
		return ResponseEntity("All customers have been deleted!", HttpStatus.OK);
	fun findByAge(@PathVariable age: Int) = repository.findByAge(age);
	fun updateCustomer(@PathVariable("id") id: Long, @RequestBody customer: Customer):  ResponseEntity {
		println("Update Customer with ID = " + id + "...");
		var customerData = repository.findById(id);
		if (customerData.isPresent()) {
			var _customer = customerData.get(); =;
			_customer.age = customer.age; =;
			return ResponseEntity(, HttpStatus.OK);
		} else {
			return ResponseEntity(HttpStatus.NOT_FOUND);
2.1.5 Configuration for Spring Datasource & JPA properties


2.2 Angular 12 Client

2.2.0 Create Service & Components

Run commands below:
ng g s Customer
ng g c CreateCustomer
ng g c CustomerDetails
ng g c CustomersList
ng g c SearchCustomers
On each Component selector, delete app- prefix, then change tslint.json rules"component-selector" to false.

2.2.1 Model


export class Customer {
    id: number;
    name: string;
    age: number;
    active: boolean;
2.2.2 CustomerService


import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';

  providedIn: 'root'
export class CustomerService {

  private baseUrl = 'http://localhost:8080/api/customers';

  constructor(private http: HttpClient) { }

  getCustomer(id: number): Observable<Object> {
    return this.http.get(`${this.baseUrl}/${id}`);

  createCustomer(customer: Object): Observable<Object> {
    return`${this.baseUrl}` + `/create`, customer);

  updateCustomer(id: number, value: any): Observable<Object> {
    return this.http.put(`${this.baseUrl}/${id}`, value);

  deleteCustomer(id: number): Observable<any> {
    return this.http.delete(`${this.baseUrl}/${id}`, { responseType: 'text' });

  getCustomersList(): Observable<any> {
    return this.http.get(`${this.baseUrl}`);

  getCustomersByAge(age: number): Observable<any> {
    return this.http.get(`${this.baseUrl}/age/${age}`);

  deleteAll(): Observable<any> {
    return this.http.delete(`${this.baseUrl}` + `/delete`, { responseType: 'text' });
2.2.3 Components

– CustomerDetailsComponent:

import { Component, OnInit, Input } from '@angular/core';
import { CustomerService } from '../customer.service';
import { Customer } from '../customer';

import { CustomersListComponent } from '../customers-list/customers-list.component';

  selector: 'customer-details',
  templateUrl: './customer-details.component.html',
  styleUrls: ['./customer-details.component.css']
export class CustomerDetailsComponent implements OnInit {

  @Input() customer: Customer;

  constructor(private customerService: CustomerService, private listComponent: CustomersListComponent) { }

  ngOnInit() {

  updateActive(isActive: boolean) {
      { name:, age: this.customer.age, active: isActive })
        data => {
          this.customer = data as Customer;
        error => console.log(error));

  deleteCustomer() {
        data => {
        error => console.log(error));


<div *ngIf="customer">
    <label>Name: </label> {{}}
    <label>Age: </label> {{customer.age}}
    <label>Active: </label> {{}}

  <span class="button is-small btn-primary" *ngIf='' (click)='updateActive(false)'>Inactive</span>

  <span class="button is-small btn-primary" *ngIf='!' (click)='updateActive(true)'>Active</span>

  <span class="button is-small btn-danger" (click)='deleteCustomer()'>Delete</span>


– CustomersListComponent:

import { Component, OnInit } from '@angular/core';
import { Observable } from 'rxjs';

import { CustomerService } from '../customer.service';
import { Customer } from '../customer';

  selector: 'customers-list',
  templateUrl: './customers-list.component.html',
  styleUrls: ['./customers-list.component.css']
export class CustomersListComponent implements OnInit {

  customers: Observable;

  constructor(private customerService: CustomerService) { }

  ngOnInit() {

  deleteCustomers() {
        data => {
        error => console.log('ERROR: ' + error));

  reloadData() {
    this.customers = this.customerService.getCustomersList();



<div *ngFor="let customer of customers | async" style="width: 300px;">
  <customer-details [customer]='customer'></customer-details>

  <button type="button" class="button btn-danger" (click)='deleteCustomers()'>Delete All</button>

– CreateCustomerComponent:

import { Component, OnInit } from '@angular/core';

import { Customer } from '../customer';
import { CustomerService } from '../customer.service';

  selector: 'create-customer',
  templateUrl: './create-customer.component.html',
  styleUrls: ['./create-customer.component.css']
export class CreateCustomerComponent implements OnInit {

  customer: Customer = new Customer();
  submitted = false;

  constructor(private customerService: CustomerService) { }

  ngOnInit() {

  newCustomer(): void {
    this.submitted = false;
    this.customer = new Customer();

  save() {
      .subscribe(data => console.log(data), error => console.log(error));
    this.customer = new Customer();

  onSubmit() {
    this.submitted = true;;


<h3>Create Customer</h3>
<div [hidden]="submitted" style="width: 300px;">
  <form (ngSubmit)="onSubmit()">
    <div class="form-group">
      <label for="name">Name</label>
      <input type="text" class="form-control" id="name" required [(ngModel)]="" name="name">

    <div class="form-group">
      <label for="age">Age</label>
      <input type="text" class="form-control" id="age" required [(ngModel)]="customer.age" name="age">

    <button type="submit" class="btn btn-success">Submit</button>

<div [hidden]="!submitted">
  <h4>You submitted successfully!</h4>
  <button class="btn btn-success" (click)="newCustomer()">Add</button>

– SearchCustomersComponent:

import { Component, OnInit } from '@angular/core';
import { Customer } from '../customer';
import { CustomerService } from '../customer.service';

  selector: 'search-customers',
  templateUrl: './search-customers.component.html',
  styleUrls: ['./search-customers.component.css']
export class SearchCustomersComponent implements OnInit {

  age: number;
  customers: Customer[];

  constructor(private dataService: CustomerService) { }

  ngOnInit() {
    this.age = 0;

  private searchCustomers() {
      .subscribe(customers => this.customers = customers);

  onSubmit() {


<h3>Find By Age</h3>
<div style="width: 300px;">
  <form (ngSubmit)="onSubmit()">
    <div class="form-group">
      <label for="lastname">Age</label>
      <input type="text" class="form-control" id="age" required [(ngModel)]="age" name="age">

    <div class="btn-group">
      <button type="submit" class="btn btn-success">Submit</button>
  <li *ngFor="let customer of customers">
    <h4>{{}} - {{}} {{customer.age}}</h4>
2.2.4 AppRoutingModule


import { NgModule } from '@angular/core';
import { RouterModule, Routes } from '@angular/router';
import { CustomersListComponent } from './customers-list/customers-list.component';
import { CreateCustomerComponent } from './create-customer/create-customer.component';
import { SearchCustomersComponent } from './search-customers/search-customers.component';

const routes: Routes = [
    { path: '', redirectTo: 'customer', pathMatch: 'full' },
    { path: 'customer', component: CustomersListComponent },
    { path: 'add', component: CreateCustomerComponent },
    { path: 'findbyage', component: SearchCustomersComponent },

    imports: [RouterModule.forRoot(routes)],
    exports: [RouterModule]

export class AppRoutingModule { }

And AppComponent HTML for routing:

<div style="padding: 20px;">
  <h1 style="color: blue">{{title}}</h1>
    <a routerLink="customer" class="btn btn-primary active" role="button" routerLinkActive="active">Customers</a>
    <a routerLink="add" class="btn btn-primary active" role="button" routerLinkActive="active">Add</a>
    <a routerLink="findbyage" class="btn btn-primary active" role="button" routerLinkActive="active">Search</a>
2.2.5 AppModule


import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { FormsModule } from '@angular/forms';

import { AppComponent } from './app.component';
import { CreateCustomerComponent } from './create-customer/create-customer.component';
import { CustomerDetailsComponent } from './customer-details/customer-details.component';
import { CustomersListComponent } from './customers-list/customers-list.component';
import { SearchCustomersComponent } from './search-customers/search-customers.component';
import { AppRoutingModule } from './app-routing.module';
import { HttpClientModule } from '@angular/common/http';

  declarations: [
  imports: [
  providers: [],
  bootstrap: [AppComponent]
export class AppModule { }

3. Run & Check Result

Build and Run Spring Boot project with commandlines: mvn clean install and mvn spring-boot:run.
– Run the Angular App with command: ng serve.

– Open browser for url http://localhost:4200/:
Add Customer:


Show Customers:

kotlin-spring-boot-angular-6-crud-httpclient-spring-rest-api-data-mysql-crud-spring-jpa + show-customers

Click on Active button to update Customer status:

kotlin-spring-boot-angular-6-crud-httpclient-spring-rest-api-data-mysql-crud-spring-jpa +update-customers

Search Customers by Age:

kotlin-spring-boot-angular-6-crud-httpclient-spring-rest-api-data-mysql-crud-spring-jpa + search-customers

Delete a Customer:

kotlin-spring-boot-angular-6-crud-httpclient-spring-rest-api-data-mysql-crud-spring-jpa + delete-customer

Delete All Customers:

kotlin-spring-boot-angular-6-crud-httpclient-spring-rest-api-data-mysql-crud-spring-jpa + delete-all-customers

IV. Source Code


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