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Spring BootBeginner10 min read2026-03-01

Spring Boot REST API Tutorial

Build a production-grade, secure REST API with Spring Boot 3, Java 21, and Spring Data JPA from scratch.

Prerequisites

  • Java Development Kit (JDK 17 or 21) installed
  • Basic understanding of object-oriented Java programming
  • Maven or Gradle installed

1. Project Initialization

Generate a new Spring Boot project via start.spring.io with dependencies: Spring Web, Spring Data JPA, and H2 Database.

xml
// pom.xml dependencies
<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>
    <dependency>
        <groupId>com.h2database</groupId>
        <artifactId>h2</artifactId>
        <scope>runtime</scope>
    </dependency>
</dependencies>

2. Creating the Domain Entity

Define a clean JPA entity with auto-generated ID, validation constraints, and getters/setters.

java
@Entity
@Table(name = "articles")
public class Article {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(nullable = false)
    private String title;

    @Column(columnDefinition = "TEXT")
    private String content;

    public Article() {}
    public Article(String title, String content) {
        this.title = title;
        this.content = content;
    }
    // Getters and Setters
}

3. Spring Data JPA Repository

Extend JpaRepository to automatically inherit full CRUD operations without writing raw SQL.

java
@Repository
public interface ArticleRepository extends JpaRepository<Article, Long> {
    List<Article> findByTitleContainingIgnoreCase(String keyword);
}

4. Building the REST Controller

Expose standard RESTful endpoints (@GetMapping, @PostMapping, @PutMapping, @DeleteMapping) returning ResponseEntity.

java
@RestController
@RequestMapping("/api/v1/articles")
public class ArticleController {
    private final ArticleRepository repository;

    public ArticleController(ArticleRepository repository) {
        this.repository = repository;
    }

    @GetMapping
    public ResponseEntity<List<Article>> getAll() {
        return ResponseEntity.ok(repository.findAll());
    }

    @PostMapping
    public ResponseEntity<Article> create(@RequestBody Article article) {
        Article saved = repository.save(article);
        return ResponseEntity.status(HttpStatus.CREATED).body(saved);
    }
}

Best Practices & Architecture Advice

  • Always use constructor injection rather than @Autowired field injection.
  • Wrap responses in ResponseEntity with appropriate HTTP status codes (201 Created, 204 No Content).
  • Use DTOs (Data Transfer Objects) instead of exposing database entities directly to API consumers.

Common Mistakes to Watch Out For

  • •Returning null from controller methods instead of throwing a NotFoundException.
  • •Mutating entities in-place without transaction boundaries.

Frequently Asked Questions

How do I test these endpoints from the terminal?

Run curl -X GET http://localhost:8080/api/v1/articles or import the endpoints into Postman.

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