JPA: Composite Primary Key with Foreign Keys

 
Entity for the ProductSales Table:

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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:

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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:

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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;     }       }