Spring Boot 3 Rest API example: CRUD Application

In this tutorial, we’re gonna build a Spring Boot 3 Rest API example with Maven that implement CRUD operations. You’ll know:

Way to define Spring Rest Controller
Way to handle HTTP GET, POST, PUT, DELETE requests for CRUD Operations
How to define Data Model and Service Component

Using databases:
– Spring Data JPA + H2
– Spring Data JPA + MySQL
– Spring Data JPA + PostgreSQL
– Spring Data JPA + SQL Server
– Spring Data + MongoDB

More Practice:
– Validate Request Body in Spring Boot
– Spring Boot WebFlux Rest API example
– Spring Boot @ControllerAdvice & @ExceptionHandler example
– @RestControllerAdvice example in Spring Boot
– Spring Boot Unit Test for Rest Controller
– Documentation: Spring Boot + Swagger 3 example (with OpenAPI 3)
– Caching: Spring Boot Redis Cache example

Fullstack:
– Spring Boot Thymeleaf example
– Vue + Spring Boot example
– Angular 8 + Spring Boot example
– Angular 10 + Spring Boot example
– Angular 11 + Spring Boot example
– Angular 12 + Spring Boot example
– Angular 13 + Spring Boot example
– Angular 14 + Spring Boot example
– Angular 15 + Spring Boot example
– Angular 16 + Spring Boot example
– React + Spring Boot example

Contents

Overview
Technology
Project Structure
Create & Setup Spring Boot project
Define Data Model
Create Data Service
Create Spring Rest APIs Controller
Run & Check
Conclusion
Source Code
Further Reading

Overview of Spring Boot Rest API example

We will build a Spring Boot 3 Rest Api using Spring Web MVC for a Tutorial application in that:

Each Tutorial has id, title, description, published status.
Apis help to create, retrieve, update, delete Tutorials.
Apis also support custom finder methods such as find by published status or by title.

These are APIs that we need to provide:

Methods	Urls	Actions
POST	/api/tutorials	create new Tutorial
GET	/api/tutorials	retrieve all Tutorials
GET	/api/tutorials/:id	retrieve a Tutorial by `:id`
PUT	/api/tutorials/:id	update a Tutorial by `:id`
DELETE	/api/tutorials/:id	delete a Tutorial by `:id`
DELETE	/api/tutorials	delete all Tutorials
GET	/api/tutorials/published	find all published Tutorials
GET	/api/tutorials?title=[keyword]	find all Tutorials which title contains `keyword`

Technology

Java 11
Spring Boot 3 (with Spring Web MVC)
Maven 3.6.1

Project Structure

Let me explain it briefly.

– Tutorial data model class.
– TutorialService is a service component that implement CRUD methods and custom finder methods. It will be autowired in TutorialController.
– TutorialController is a RestController which has request mapping methods for RESTful requests such as: getAllTutorials, createTutorial, updateTutorial, deleteTutorial, findByPublished…

Create & Setup Spring Boot project

Use Spring web tool or your development tool (Spring Tool Suite, Eclipse, Intellij) to create a Spring Boot project.

Then open pom.xml and add these dependencies:

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-web</artifactId>
</dependency>

Define Data Model

Our Data model is Tutorial with four fields: id, title, description, published.
In model package, we define Tutorial class.

model/Tutorial.java

package com.bezkoder.spring.restapi.model;

public class Tutorial {
  private long id = 0;

  private String title;

  private String description;

  private boolean published;

  public Tutorial() {

  }

  public Tutorial(String title, String description, boolean published) {
    this.title = title;
    this.description = description;
    this.published = published;
  }

  public void setId(long id) {
    this.id = id;
  }
  
  public long getId() {
    return id;
  }

  public String getTitle() {
    return title;
  }

  public void setTitle(String title) {
    this.title = title;
  }

  public String getDescription() {
    return description;
  }

  public void setDescription(String description) {
    this.description = description;
  }

  public boolean isPublished() {
    return published;
  }

  public void setPublished(boolean isPublished) {
    this.published = isPublished;
  }

  @Override
  public String toString() {
    return "Tutorial [id=" + id + ", title=" + title + ", desc=" + description + ", published=" + published + "]";
  }

}

Create Data Service

Let’s create a service to implement CRUD Operations on the Tutorial model.
In service package, create TutorialService.

service/TutorialService.java

package com.bezkoder.spring.restapi.service;

import java.util.ArrayList;
import java.util.List;

import org.springframework.stereotype.Service;

import com.bezkoder.spring.restapi.model.Tutorial;

@Service
public class TutorialService {

  static List<Tutorial> tutorials = new ArrayList<Tutorial>();
  static long id = 0;

  public List<Tutorial> findAll() {
    return tutorials;
  }

  public List<Tutorial> findByTitleContaining(String title) {
    return tutorials.stream().filter(tutorial -> tutorial.getTitle().contains(title)).toList();
  }

  public Tutorial findById(long id) {
    return tutorials.stream().filter(tutorial -> id == tutorial.getId()).findAny().orElse(null);
  }

  public Tutorial save(Tutorial tutorial) {
    // update Tutorial
    if (tutorial.getId() != 0) {
      long _id = tutorial.getId();

      for (int idx = 0; idx < tutorials.size(); idx++)
        if (_id == tutorials.get(idx).getId()) {
          tutorials.set(idx, tutorial);
          break;
        }

      return tutorial;
    }

    // create new Tutorial
    tutorial.setId(++id);
    tutorials.add(tutorial);
    return tutorial;
  }

  public void deleteById(long id) {
    tutorials.removeIf(tutorial -> id == tutorial.getId());
  }

  public void deleteAll() {
    tutorials.removeAll(tutorials);
  }

  public List<Tutorial> findByPublished(boolean isPublished) {
    return tutorials.stream().filter(tutorial -> isPublished == tutorial.isPublished()).toList();
  }
}

Create Spring Rest APIs Controller

Finally, we create a controller that provides APIs for creating, retrieving, updating, deleting and finding Tutorials.

controller/TutorialController.java

package com.bezkoder.spring.restapi.controller;

import java.util.ArrayList;
import java.util.List;

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.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import com.bezkoder.spring.restapi.model.Tutorial;
import com.bezkoder.spring.restapi.service.TutorialService;

@CrossOrigin(origins = "http://localhost:8081")
@RestController
@RequestMapping("/api")
public class TutorialController {
  @Autowired
  TutorialService tutorialService;

  @GetMapping("/tutorials")
  public ResponseEntity<List<Tutorial>> getAllTutorials(@RequestParam(required = false) String title) {
    try {
      List<Tutorial> tutorials = new ArrayList<Tutorial>();

      if (title == null)
        tutorialService.findAll().forEach(tutorials::add);
      else
        tutorialService.findByTitleContaining(title).forEach(tutorials::add);

      if (tutorials.isEmpty()) {
        return new ResponseEntity<>(HttpStatus.NO_CONTENT);
      }

      return new ResponseEntity<>(tutorials, HttpStatus.OK);
    } catch (Exception e) {
      return new ResponseEntity<>(null, HttpStatus.INTERNAL_SERVER_ERROR);
    }
  }

  @GetMapping("/tutorials/{id}")
  public ResponseEntity<Tutorial> getTutorialById(@PathVariable("id") long id) {
    Tutorial tutorial = tutorialService.findById(id);

    if (tutorial != null) {
      return new ResponseEntity<>(tutorial, HttpStatus.OK);
    } else {
      return new ResponseEntity<>(HttpStatus.NOT_FOUND);
    }
  }

  @PostMapping("/tutorials")
  public ResponseEntity<Tutorial> createTutorial(@RequestBody Tutorial tutorial) {
    try {
      Tutorial _tutorial = tutorialService
          .save(new Tutorial(tutorial.getTitle(), tutorial.getDescription(), false));
      return new ResponseEntity<>(_tutorial, HttpStatus.CREATED);
    } catch (Exception e) {
      return new ResponseEntity<>(null, HttpStatus.INTERNAL_SERVER_ERROR);
    }
  }

  @PutMapping("/tutorials/{id}")
  public ResponseEntity<Tutorial> updateTutorial(@PathVariable("id") long id, @RequestBody Tutorial tutorial) {
    Tutorial _tutorial = tutorialService.findById(id);

    if (_tutorial != null) {
      _tutorial.setTitle(tutorial.getTitle());
      _tutorial.setDescription(tutorial.getDescription());
      _tutorial.setPublished(tutorial.isPublished());
      return new ResponseEntity<>( tutorialService.save(_tutorial), HttpStatus.OK);
    } else {
      return new ResponseEntity<>(HttpStatus.NOT_FOUND);
    }
  }

  @DeleteMapping("/tutorials/{id}")
  public ResponseEntity<HttpStatus> deleteTutorial(@PathVariable("id") long id) {
    try {
      tutorialService.deleteById(id);
      return new ResponseEntity<>(HttpStatus.NO_CONTENT);
    } catch (Exception e) {
      return new ResponseEntity<>(HttpStatus.INTERNAL_SERVER_ERROR);
    }
  }

  @DeleteMapping("/tutorials")
  public ResponseEntity<HttpStatus> deleteAllTutorials() {
    try {
      tutorialService.deleteAll();
      return new ResponseEntity<>(HttpStatus.NO_CONTENT);
    } catch (Exception e) {
      return new ResponseEntity<>(HttpStatus.INTERNAL_SERVER_ERROR);
    }

  }

  @GetMapping("/tutorials/published")
  public ResponseEntity<List<Tutorial>> findByPublished() {
    try {
      List<Tutorial> tutorials =  tutorialService.findByPublished(true);

      if (tutorials.isEmpty()) {
        return new ResponseEntity<>(HttpStatus.NO_CONTENT);
      }
      return new ResponseEntity<>(tutorials, HttpStatus.OK);
    } catch (Exception e) {
      return new ResponseEntity<>(HttpStatus.INTERNAL_SERVER_ERROR);
    }
  }
}

– @CrossOrigin is for configuring allowed origins.
– @RestController annotation is used to define a controller and to indicate that the return value of the methods should be be bound to the web response body.
– @RequestMapping("/api") declares that all Apis’ url in the controller will start with /api.
– We use @Autowired to inject TutorialService bean to local variable.

You can find way to write Unit test for this Controller at:
Spring Boot Unit Test for Rest Controller

Run & Check

Run Spring Boot application with command: mvn spring-boot:run.

Create some Tutorials:

Retrieve all Tutorials:

Update some Tutorials:

Retrieve a Tutorial by Id:

Find all published Tutorials:

Find all Tutorials which title contains string ‘new’:

Delete a Tutorial:

Check all current Tutorials:

Delete all Tutorials and check:

You can also test this Spring Boot App with Client in one of these posts:

Conclusion

Today we’ve built a Spring Boot 3 Rest API – CRUD example using Spring Web.

If you want to keep data after restarting the Application without using another complex database, you can use embedded database (H2):
Spring Boot JPA + H2 example: Build a CRUD Rest API

Happy learning! See you again.

Source Code

You can find the complete source code for this tutorial on Github.