Spring Boot REST API One-to-Many CRUD Operations Example

Author:
In this tutorial, we will demonstrate how to set up a one-to-many relationship between Author and Book entities using Spring Boot and Hibernate, and expose CRUD operations through a REST API.

Prerequisites

  1. Java Development Kit (JDK) 11 or higher: Ensure JDK is installed and configured on your system.
  2. Integrated Development Environment (IDE): IntelliJ IDEA, Eclipse, or any other IDE.
  3. Maven: Ensure Maven is installed and configured on your system.

Step 1: Create a Spring Boot Project

  1. Open your IDE and create a new Spring Boot project.
  2. Use Spring Initializr or manually create the pom.xml file to include Spring Boot and other required dependencies.
<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.example</groupId>
    <artifactId>spring-boot-onetomany-example</artifactId>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.1.0</version>
        <relativePath/>
    </parent>

    <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-web</artifactId>
        </dependency>
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <scope>runtime</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

Explanation

  • spring-boot-starter-data-jpa: Includes Spring Data JPA with Hibernate.
  • spring-boot-starter-web: Includes Spring MVC for building web applications.
  • h2: An in-memory database for testing purposes.

Step 2: Configure the Application Properties

Configure the application.properties file to set up the H2 database.

spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
spring.h2.console.enabled=true
spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true
spring.jpa.properties.hibernate.format_sql=true

Step 3: Create the Author Entity Class

Create a package named com.example.entity and a class named Author.

package com.example.entity;

import jakarta.persistence.*;
import java.util.HashSet;
import java.util.Set;

@Entity
public class Author {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;

    @OneToMany(mappedBy = "author", cascade = CascadeType.ALL, orphanRemoval = true)
    private Set<Book> books = new HashSet<>();

    public Author() {}

    public Author(String name) {
        this.name = name;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Set<Book> getBooks() {
        return books;
    }

    public void setBooks(Set<Book> books) {
        this.books = books;
    }

    public void addBook(Book book) {
        books.add(book);
        book.setAuthor(this);
    }

    public void removeBook(Book book) {
        books.remove(book);
        book.setAuthor(null);
    }

    @Override
    public String toString() {
        return "Author{id=" + id + ", name='" + name + '\'' + '}';
    }
}

Explanation

  • @Entity: Marks the class as an entity.
  • @Id: Marks the field as the primary key.
  • @GeneratedValue: Specifies the strategy for generating values for the primary key.
  • @OneToMany: Defines a one-to-many relationship with the Book entity.
  • mappedBy: Specifies the field in the Book entity that owns the relationship.
  • cascade: Specifies the cascade operations.
  • orphanRemoval: Specifies whether to remove orphaned entities.

Step 4: Create the Book Entity Class

Create a class named Book in the same package.

package com.example.entity;

import jakarta.persistence.*;

@Entity
public class Book {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String title;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "author_id")
    private Author author;

    public Book() {}

    public Book(String title) {
        this.title = title;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

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

    public Author getAuthor() {
        return author;
    }

    public void setAuthor(Author author) {
        this.author = author;
    }

    @Override
    public String toString() {
        return "Book{id=" + id + ", title='" + title + '\'' + '}';
    }
}

Explanation

  • @Entity: Marks the class as an entity.
  • @Id: Marks the field as the primary key.
  • @GeneratedValue: Specifies the strategy for generating values for the primary key.
  • @ManyToOne: Defines a many-to-one relationship with the Author entity.
  • @JoinColumn: Specifies the foreign key column.

Step 5: Create Repository Interfaces

Create a package named com.example.repository and interfaces for Author and Book.

package com.example.repository;

import com.example.entity.Author;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface AuthorRepository extends JpaRepository<Author, Long> {}

package com.example.repository;

import com.example.entity.Book;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface BookRepository extends JpaRepository<Book, Long> {}

Step 6: Create Service Classes

Create a package named com.example.service and service classes for Author and Book.

package com.example.service;

import com.example.entity.Author;
import com.example.entity.Book;
import com.example.repository.AuthorRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class AuthorService {
    @Autowired
    private AuthorRepository authorRepository;

    public Author save(Author author) {
        return authorRepository.save(author);
    }

    public List<Author> findAll() {
        return authorRepository.findAll();
    }

    public Author findById(Long id) {
        return authorRepository.findById(id).orElse(null);
    }

    public void deleteById(Long id) {
        authorRepository.deleteById(id);
    }

    public Author addBook(Long authorId, Book book) {
        Author author = findById(authorId);
        if (author != null) {
            author.addBook(book);
            return save(author);
        }
        return null;
    }

    public Author removeBook(Long authorId, Long bookId) {
        Author author = findById(authorId);
        if (author != null) {
            Book book = author.getBooks().stream().filter(b -> b.getId().equals(bookId)).findFirst().orElse(null);
            if (book != null) {
                author.removeBook(book);
                return save(author);
            }
        }
        return null;
    }
}

package com.example.service;

import com.example.entity.Book;
import com.example.repository.BookRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class BookService {
    @Autowired
    private BookRepository bookRepository;

    public Book save(Book book) {
        return bookRepository.save(book);
    }

    public List<Book> findAll() {
        return bookRepository.findAll();
    }

    public Book findById(Long id) {
        return bookRepository.findById(id).orElse(null);
    }

    public void deleteById(Long id) {
        bookRepository.deleteById(id);
    }
}

Step 7: Create Controller Classes

Create a package named com.example.controller and controller classes for Author and Book.

package com.example.controller;

import com.example.entity.Author;
import com.example.entity.Book;
import com.example.service.AuthorService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/authors")
public class AuthorController {
    @Autowired
    private AuthorService authorService;

    @PostMapping
    public Author createAuthor(@RequestBody Author author) {
        return authorService.save(author);
    }

    @GetMapping
    public List<Author> getAllAuthors() {
        return authorService.findAll();
    }

    @GetMapping("/{id}")
    public Author getAuthorById(@PathVariable Long id) {
        return authorService.findById(id);
    }

    @DeleteMapping("/{id}")
    public void deleteAuthor(@PathVariable Long id) {
        authorService.deleteById(id);
    }

    @PostMapping("/{authorId}/books")
    public Author addBook(@PathVariable Long authorId, @RequestBody Book book) {
        return authorService.addBook(authorId, book);
    }

    @DeleteMapping("/{authorId}/books/{bookId}")
    public Author removeBook(@PathVariable Long authorId, @PathVariable Long bookId) {
        return authorService.removeBook(authorId, bookId);
    }
}

package com.example.controller;

import com.example.entity.Book;
import com.example.service.BookService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/books")
public class BookController {
    @Autowired
    private BookService bookService;

    @PostMapping
    public Book createBook(@RequestBody Book book) {
        return bookService.save(book);
    }

    @GetMapping
    public List<Book> getAllBooks() {
        return bookService.findAll();
    }

    @GetMapping("/{id}")
    public Book getBookById(@PathVariable Long id) {
        return bookService.findById(id);
    }

    @DeleteMapping("/{id}")
    public void deleteBook(@PathVariable Long id) {
        bookService.deleteById(id);
    }
}

Step 8: Create Main Application Class

Create a package named com.example and a class named SpringBootOneToManyExampleApplication.

package com.example;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringBootOneToManyExampleApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringBootOneToManyExampleApplication.class, args);
    }
}

Step 9: Run the Application

  1. Run the SpringBootOneToManyExampleApplication class.
  2. Use an API client (e.g., Postman) or a web browser to test the endpoints.

Testing the Endpoints

  1. Create an Author:

    • URL: POST /authors
    • Body: 
      {
  "name": "George Orwell"
}

  2. Create Books:

    • URL: POST /books
    • Body: 
      {
  "title": "1984"
}
    • Body: 
      {
  "title": "Animal Farm"
}

  3. Add Books to Author:

    • URL: POST /authors/{authorId}/books
    • Body: 
      {
  "title": "1984"
}
    • Body: 
      {
  "title": "Animal Farm"
}

  4. Get All Authors:

    • URL: GET /authors

  5. Get Author by ID:

    • URL: GET /authors/{id}

  6. Get All Books:

    • URL: GET /books

  7. Get Book by ID:

    • URL: GET /books/{id}

  8. Delete Author by ID:

    • URL: DELETE /authors/{id}

  9. Delete Book by ID:

    • URL: DELETE /books/{id}

Conclusion

You have successfully created an example using Spring Boot and Hibernate to demonstrate a one-to-many relationship in an e-commerce context. This tutorial covered setting up a Spring Boot project, configuring Hibernate, creating entity classes with a one-to-many relationship, and performing CRUD operations through RESTful endpoints.

Related Spring and Spring Boot Tutorials/Guides:

Spring Boot Tutorials [500+] Spring Boot Testing Tutorial Spring Boot Microservice Tutorial Spring Boot Kafka Microservices Spring Boot + Apache Kafka Tutorial Spring Core Tutorial Spring MVC Tutorial Spring Data JPA Tutorial Spring Framework for Beginners Spring AOP Tutorial Spring Security Tutorial Spring Exceptions Tutorial Spring Boot Interview Questions Spring Boot Microservices Interview Questions Apache Kafka Tutorials Docker Tutorials and Guides Spring Boot RabbitMQ Tutorials Angular CRUD Example with Spring Boot Spring Boot + Angular 12 CRUD Full Stack Spring Boot + Angular 8 CRUD Full Stack Spring Boot + Angular 10 CRUD Full Stack Spring Boot + React JS CRUD Full Stack React JS ( React Hooks) + Spring Boot Spring Boot Thymeleaf CRUD Full Stack Spring Boot User Registration and Login Node Js + Express + MongoDB CRUD Vue JS + Spring Boot REST API Tutorial

Comments

Post a Comment

Leave Comment