Hibernate - One-to-Many Mapping

Last Updated : 26 Aug, 2025

Hibernate is an ORM (Object-Relational Mapping) framework in Java that allows developers to map Java objects to database tables. One of the common relationships in databases is One-to-Many, where one record in a parent table can be associated with multiple records in a child table. Hibernate makes it easy to implement this relationship in Java.

Real-Life Example

Consider bike manufacturers:

A manufacturer can produce multiple bike models.
The same bike model cannot be produced by multiple manufacturers.

This is a classic one-to-many relationship, where one manufacturer>many models.

Syntax:

This mapped variable of the other tables is responsible for mapping between two tables.

@oneToMany(mappedby=”nameofmappedvariable”)

For this example, we will map the id field of m to the manufacture_id of the model entity.

Link between the table

Step by Step Implementation

Step 1. Create the MySQL database

CREATE DATABASE mapping;

Step 2. Generate the starter project (spring Initializr)

Project: Maven
Language: Java
Spring Boot: 2.5.7
Packaging: JAR
Java: 11
Dependencies:

Spring Web
Spring Data JPA
MySql Driver

Click Generate

Step 3. Importing the Project

Open your IDE.
File > New > Project from Existing Sources.
Select pom.xml and import the project.

Step 4: Database configuration

Database configuration required for connection of Mysql database to the Spring Boot Application.

application.properties

spring.datasource.username=root
spring.datasource.password=Aayush
spring.datasource.url=jdbc:mysql://localhost:3306/mapping
spring.jpa.hibernate.ddl-auto=update

Step 5: Create folder structure

Go to src-> main -> java -> com -> example -> Mapping and create two files in the models folder i.e Manufactures.java and Model.java

Step 6: Add entity

1. Create Manufactures.java class : This contains the entity Manufactures, which contains the required associated fields.

Manufactures.java class

Java

package com.example.Mapping.Models;

import javax.persistence.*;
import java.util.List;

@Entity
@Table(name = "manufactures")
public class Manufactures {

    // Unique identifier for the manufacturer
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    // Name of the manufacturer
    private String manufactures_name;

    // A manufacturer can have many models
    @OneToMany(mappedBy = "manufacturer", cascade = CascadeType.ALL)
private List<Model> models;

    // Constructor with both id and name
    public Manufactures(String manufactures_name) {
    this.manufactures_name = manufactures_name;
}

    // Default constructor
    public Manufactures() {
    }

    // Getters and setters for id and name

    public int getId() {
        return id;
    }

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

    public String getManufactures_name() {
        return manufactures_name;
    }

    public void setManufactures_name(String manufactures_name) {
        this.manufactures_name = manufactures_name;
    }

    // Getter for models
    public List<Model> getModels() {
        return models;
    }

    // Setter for models
    public void setModels(List<Model> models) {
        this.models = models;
    }
}

2. Create Model.java

This contains the entity Model with various fields and methods-

Java

package com.example.Mapping.Models;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;

@Entity
@Table(name = "models")
public class Model {

    // Unique identifier for the model
    @Id
    private int model_id;

    // Name of the model
    private String name;

    // A model belongs to one manufacturer Foreign key referencing the manufacturer table
    @ManyToOne
    @JoinColumn(name = "manufacture_id")
    private Manufactures manufacturer;

    // Constructor with all fields
    public Model(int model_id, String name, Manufactures manufacturer) {
        this.model_id = model_id;
        this.name = name;
        this.manufacturer = manufacturer;
    }

    // Default constructor
    public Model() {
    }

    // Getters and setters

    public int getModel_id() {
        return model_id;
    }

    public void setModel_id(int model_id) {
        this.model_id = model_id;
    }

    public String getName() {
        return name;
    }

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

    public Manufactures getManufacturer() {
        return manufacturer;
    }

    public void setManufacturer(Manufactures manufacturer) {
        this.manufacturer = manufacturer;
    }
}

Step 7. Add repositories

1. Create ManufactureRepo Class: This Interface contains the forms the bridge of entity Manufactures to the Database

ManufacturesRepo.java

Java

package com.example.Mapping.Repositories;

import com.example.Mapping.Models.Manufactures;
import org.springframework.data.jpa.repository.JpaRepository;

public interface ManufacturesRepo extends JpaRepository<Manufactures, Integer> {
}

2. Create ModelRepo.java class: This Interface contains the forms the bridge of entity Model to the Database

ModelRepo.java

Java

package com.example.Mapping.Repositories;

import com.example.Mapping.Models.Model;
import org.springframework.data.jpa.repository.JpaRepository;

public interface ModelRepo extends JpaRepository<Model, Integer> {
}

Step 8. Application drive

Driver class for Spring Boot application to test the One-to-Many Mapping of Hibernate.

This Spring Boot application initializes and saves data using JPA repositories.
It creates a Manufacturer("Honda") entity and two associated Model ("AYZ" and "ZET") entities with a one-to-many relationship.
The data is then stored in corresponding repositories during the application's run.

MappingApplication.java

Java

package com.example.Mapping;

import com.example.Mapping.Models.Manufactures;
import com.example.Mapping.Models.Model;
import com.example.Mapping.Repositories.ManufacturesRepo;
import com.example.Mapping.Repositories.ModelRepo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

/**
 * Spring Boot application for mapping relationships between Manufactures and Models.
 */
@SpringBootApplication
public class MappingApplication implements CommandLineRunner {

    // Injecting Manufactures and Model repositories using autowiring
    @Autowired
    private ManufacturesRepo manufacturesRepo;
    @Autowired
    private ModelRepo modelRepo;

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

    @Override
    public void run(String... args) throws Exception {

        // Creating a new Manufactures object with ID 1 and name "Honda"
        Manufactures data = new Manufactures("Honda");

        // Saving the Manufactures record
        manufacturesRepo.save(data);

        // Creating two new Model objects associated with the "Honda" manufacturer
        Model model1 = new Model(1, "AYZ", data);
        Model model2 = new Model(2, "ZET", data);

        // Saving the Model records
        modelRepo.save(model1);
        modelRepo.save(model2);
    }
}