Spring JPA Hibernate One to Many Relationship - SpringBoot + MySQL

spring jpa

9

hibernate

7

springboot

136

Mysql

85

loveprogramming viết ngày 03/04/2021

I. Technologies

– Java 1.8
– Maven 3.3.9
– Spring Tool Suite – Version 3.8.1.RELEASE
– Spring Boot: 1.5.6.RELEASE
– MySql database

II. Practice - Spring JPA One to Many Relationship

Step to do

• Create SpringBoot project
• Create Models
• Create JPA Repositories
• Configure Datasource & Spring JPA
• Implement a test Client
• Run & Check results

  1. Create SpringBoot project

  – Using SpringToolSuite, create a SpringBoot project. Then add needed dependencies:

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

<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>

<dependency>
<groupId>org.json</groupId>
<artifactId>json</artifactId>
</dependency>

2. Create Models

2 Entities Company and Product that having One-to-Many relationship:

2.1 Company entity

package com.javasampleapproach.jpa.one2many.model;

import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

import org.json.JSONArray;
import org.json.JSONObject;

@Entity
@Table(name="company")
public class Company {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;
    private String name;
    
    @OneToMany(mappedBy = "company", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    private Set products;
    
    public Company(){
    }
    
    public Company(String name){
        this.name = name;
    }
    
    // name
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    
    // products
    public void setProducts(Set products){
        this.products = products;
    }
    
    public Set getProducts(){
        return this.products;
    }
    
    public String toString(){
        String info = "";
        JSONObject jsonInfo = new JSONObject();
        jsonInfo.put("name",this.name);
        
        JSONArray productArray = new JSONArray();
        if(this.products != null){
            this.products.forEach(product->{
                JSONObject subJson = new JSONObject();
                subJson.put("name", product.getName());
                productArray.put(subJson);
            });
        }
        jsonInfo.put("products", productArray);
        info = jsonInfo.toString();
        return info;
    }
}

More tutorial: https://grokonez.com/spring-framework/spring-data/configure-spring-jpa-one-to-many-relationship-springboot