Kotlin Spring Boot + Angular 6 CRUD + PostgreSQL example | Spring Data JPA + REST APIs example

In this tutorial, we show you Angular 6 Http Client & Spring Boot Server example that uses Spring JPA to do CRUD with PostgreSQL and Angular 6 as a front-end technology to make request and receive response.

Related Posts:
– How to use Spring JPA with PostgreSQL | Spring Boot
– Spring JPA + PostgreSQL + AngularJS example | Spring Boot
– Kotlin Spring JPA + Postgresql | Spring Boot Example
– Kotlin RequestMapping RESTful APIs with @GetMapping, @PostMapping, @PutMapping, @DeleteMapping
– Kotlin SpringJPA Hibernate One-To-Many relationship

Related Pages:

• Kotlin
• Angular
• SpringBoot

I. Technologies

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

II. Overview

1. Spring Boot Server

2. Angular 6 Client

III. Practice

1. Project Structure

1.1 Spring Boot Server

– 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 application.properties
– Dependencies for Spring Boot and PostgreSQL in pom.xml

1.2 Angular 6 Client

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 Kotlin Spring Boot Server

2.1.1 Dependency

<dependency>
	<groupId>org.jetbrains.kotlin</groupId>
	<artifactId>kotlin-stdlib-jdk8</artifactId>
</dependency>
<dependency>
	<groupId>org.jetbrains.kotlin</groupId>
	<artifactId>kotlin-reflect</artifactId>
</dependency>
<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
 
<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-web</artifactId>
</dependency>
 
<dependency>
	<groupId>org.postgresql</groupId>
	<artifactId>postgresql</artifactId>
	<scope>runtime</scope>
</dependency>

2.1.2 Customer – Data Model

model/Customer.java

package com.ozenero.springrest.postgresql.model

import javax.persistence.Entity
import javax.persistence.Id
import javax.persistence.GeneratedValue
import javax.persistence.GenerationType
 
@Entity
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= + ${this.id} + , name= + ${this.name} + , age= + ${this.age} + , active= + ${this.active} + ]";
	}
}

2.1.3 JPA Repository

repo/CustomerRepository.java

package com.ozenero.springrest.postgresql.repo;

import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;

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

@Repository
interface CustomerRepository : CrudRepository {
	fun findByAge(age: Int): Iterable
}

2.1.4 REST Controller

controller/CustomerController.java

package com.ozenero.springrest.postgresql.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.postgresql.repo.CustomerRepository
import com.ozenero.springrest.postgresql.model.Customer

@CrossOrigin(origins = arrayOf("http://localhost:4200"))
@RestController
@RequestMapping("/api")
class CustomerController {
	@Autowired
	lateinit var repository: CustomerRepository
	
	@GetMapping("/customers")
	fun findAll() = repository.findAll()
	
	@PostMapping("/customers/create")
	fun postCustomer(@RequestBody customer: Customer): Customer{
		return repository.save( Customer(customer.name, customer.age));
	}
	
	@DeleteMapping("/customers/{id}")
	fun deleteCustomer(@PathVariable("id") id: Long): ResponseEntity{
		println("Delete Customer with ID = " + id + "...");
		repository.deleteById(id);
		return ResponseEntity("Customer has been deleted!", HttpStatus.OK);
	}
	
	@DeleteMapping("/customers/delete")
	fun deleteAllCustomers(): ResponseEntity{
		println("Delete All Customers...");
		repository.deleteAll();
		return ResponseEntity("All customers have been deleted!", HttpStatus.OK);
	}
	
	@GetMapping("customers/age/{age}")
	fun findByAge(@PathVariable age: Int) = repository.findByAge(age);
 
	@PutMapping("/customers/{id}")
	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.name = customer.name;
			_customer.age = customer.age;
			_customer.active = customer.active;
			return ResponseEntity(repository.save(_customer), HttpStatus.OK);
		} else {
			return ResponseEntity(HttpStatus.NOT_FOUND);
		}
	}
}

2.1.5 Configuration for Spring Datasource & JPA properties

application.properties

spring.datasource.url=jdbc:postgresql://localhost/testdb
spring.datasource.username=postgres
spring.datasource.password=123
spring.jpa.generate-ddl=true

2.2 Angular 6 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

customer.ts

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

2.2.2 CustomerService

customer.service.ts

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

@Injectable({
  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.http.post(`${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:
customer-details/customer-details.component.ts

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

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

@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) {
    this.customerService.updateCustomer(this.customer.id,
      { name: this.customer.name, age: this.customer.age, active: isActive })
      .subscribe(
        data => {
          console.log(data);
          this.customer = data as Customer;
        },
        error => console.log(error));
  }

  deleteCustomer() {
    this.customerService.deleteCustomer(this.customer.id)
      .subscribe(
        data => {
          console.log(data);
          this.listComponent.reloadData();
        },
        error => console.log(error));
  }
}

customer-details/customer-details.component.html

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

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

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

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

  <hr/>
</div>

– CustomersListComponent:
customers-list/customers-list.component.ts

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

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

@Component({
  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() {
    this.reloadData();
  }

  deleteCustomers() {
    this.customerService.deleteAll()
      .subscribe(
        data => {
          console.log(data);
          this.reloadData();
        },
        error => console.log('ERROR: ' + error));
  }

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

customers-list/customers-list.component.html

<h1>Customers</h1>

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

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

– CreateCustomerComponent:
create-customer/create-customer.component.ts

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

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

@Component({
  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() {
    this.customerService.createCustomer(this.customer)
      .subscribe(data => console.log(data), error => console.log(error));
    this.customer = new Customer();
  }

  onSubmit() {
    this.submitted = true;
    this.save();
  }
}

create-customer/create-customer.component.html

<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)]="customer.name" name="name">
    </div>

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

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

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

– SearchCustomersComponent:
search-customers/search-customers.component.ts

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

@Component({
  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() {
    this.dataService.getCustomersByAge(this.age)
      .subscribe(customers => this.customers = customers);
  }

  onSubmit() {
    this.searchCustomers();
  }
}

search-customers/search-customers.component.html

<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>

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

2.2.4 AppRoutingModule

app-routing.module.ts

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 },
];

@NgModule({
    imports: [RouterModule.forRoot(routes)],
    exports: [RouterModule]
})

export class AppRoutingModule { }

And AppComponent HTML for routing:
app.component.html

<div style="padding: 20px;">
  <h1 style="color: blue">{{title}}</h1>
  <h3>{{description}}</h3>
  <nav>
    <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>
  </nav>
  <router-outlet></router-outlet>
</div>

2.2.5 AppModule

app.module.ts

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';

@NgModule({
  declarations: [
    AppComponent,
    CreateCustomerComponent,
    CustomerDetailsComponent,
    CustomersListComponent,
    SearchCustomersComponent
  ],
  imports: [
    BrowserModule,
    FormsModule,
    AppRoutingModule,
    HttpClientModule
  ],
  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:

Click on Active button to update Customer status:

Search Customers by Age:

Delete a Customer:

Delete All Customers:

IV. Source Code

– SpringKotlinRestAPIsPostgreSQL
– Angular6SpringBoot-Client