Hibernate OnetoMany Mapping (original) (raw)

Hibernate - One-to-Many Mapping

Last Updated : 9 Apr, 2026

Hibernate One-to-Many mapping defines a relationship where one entity is associated with multiple instances of another entity. It is commonly used to model parent-child relationships in database-driven applications. Hibernate simplifies this by managing the association and underlying database operations.

Supports bidirectional mapping for navigation from both parent and child
Provides cascade options to propagate operations like save and delete
Uses collections (List/Set) to store multiple child entities

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

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.

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

Project Bootstrap

Step 3. Importing the Project

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

Options to open 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

Directory view

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 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);
```
}

}

**Run the main application:

Console log of project running.

Console logs

**Step 9. Verify the DB content

Database view of _manufactures table:

SELECT * FROM manufactures;

Tabular view of database

**Model Table

Database view of _model table:

SELECT * FROM model;

Tablur view of model table

The below image depicts rows in manufactures and model. model will contain manufacture_id values linking to manufactures.

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