JPA: Composite Primary Key with Foreign Keys

 
Entity for the ProductSales Table:

package com.example.model;

import javax.persistence.*;

@Entity
@IdClass(ProductSalesPK.class)
public class ProductSales {

 @Column(name = "QUANTITY")
 private int quantity_sold;

 @Id
 @ManyToOne
 @JoinColumn(name = "sales_id")
 private Sales sales;

 @Id
 @ManyToOne
 @JoinColumn(name = "product_id")
 private Product product;

 public ProductSales() {
 }

 public ProductSales(Sales sales, Product product, int quantity_sold) {
  this.sales = sales;
  this.product = product;
  this.quantity_sold = quantity_sold;
 }

 public Product getProduct() {
  return product;
 }

 public Sales getSales() {
  return sales;
 }

 public void setProduct(Product product) {
  this.product = product;
 }

 public void setSales(Sales sales) {
  this.sales = sales;
 }

 public int getQuantity_sold() {
  return quantity_sold;
 }

 public void setQuantity_sold(int quantity_sold) {
  this.quantity_sold = quantity_sold;
 }
}

ProductSalesPK Id class:

package com.example.model;

import java.util.Objects;

public class ProductSalesPK {
    private int sales;
    private String product;

 public ProductSalesPK(int sales_id, String product_id) {
  this.sales = sales_id;
  this.product = product_id;
 }

 @Override
 public int hashCode() {
  int hash = 5;
  hash = 83 * hash + this.sales;
  hash = 83 * hash + Objects.hashCode(this.product);
  return hash;
 }

 @Override
 public boolean equals(Object obj) {
  if (obj == null) {
   return false;
  }
  if (getClass() != obj.getClass()) {
   return false;
  }
  final ProductSalesPK other = (ProductSalesPK) obj;
  if (this.sales != other.sales) {
   return false;
  }
  if (!Objects.equals(this.product, other.product)) {
   return false;
  }
  return true;
 } 
}

Entity class fpor Product:

package com.example.model;
package com.example.model;

import java.util.Objects;
import javax.persistence.*;
import javax.validation.constraints.*;
@Entity
public class Product {
 @NotNull(message="product id not null") @Size (min = 1,message="product id not empty") 
 @Id
    private String product_id; 
 @NotNull(message="product name not null") @Size (min = 10,message="product name length at least 10")
    private String prod_name;
 @Min(value=5, message="price >= {value}")
    private double price;
    private String prod_desc;

 public Product() {
 }

  
    public Product(String id, String name, double price, String description) {
        this.product_id = id;
        this.prod_name = name;
        this.price = price;
        this.prod_desc = description;
    }

    public String getId() {
        return product_id;
    }

    public String getName() {
        return prod_name;
    }

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

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public String getDescription() {
        return prod_desc;
    }

    public void setDescription(String description) {
        this.prod_desc = description;
    }
    
    @Override
    public String toString() {
        String s = String.format("Product id: %s\n"
        + "Name: %s\n"
        + "Description: %s\n"
        + "Price: $%.2f", product_id, prod_name, prod_desc, price);
        return s;
    }

    @Override
    public int hashCode() {
        int hash = 3;
        hash = 97 * hash + Objects.hashCode(this.product_id);
        hash = 97 * hash + Objects.hashCode(this.prod_name);
        hash = 97 * hash + (int) (Double.doubleToLongBits(this.price) ^ (Double.doubleToLongBits(this.price) >>> 32));
        hash = 97 * hash + Objects.hashCode(this.prod_desc);
        return hash;
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null) {
            return false;
        }
        if (getClass() != obj.getClass()) {
            return false;
        }
        final Product other = (Product) obj;
        if (!Objects.equals(this.product_id, other.product_id)) {
            return false;
        }
        if (!Objects.equals(this.prod_name, other.prod_name)) {
            return false;
        }
        if (Double.doubleToLongBits(this.price) != Double.doubleToLongBits(other.price)) {
            return false;
        }
        if (!Objects.equals(this.prod_desc, other.prod_desc)) {
            return false;
        }
        return true;
    }
    
}