Question

If I have 3 tables, with the expected normal columns : Customer, CustomerProductLinker and Product.

And I want in my Java code to do this :

Customer customer =  myService.getCustomer(id); //calls hibernate session
List<Product> customerProducts = customer.getProducts();

What would my 3 entities look like and the respective collections within each, specifically the getProducts() method ? Or is it better to use HQL and a named query for this ?

I am creating the databse tables from the java code (using the create option in hibernate conf), so the table desgin can be altered if preferred.

Answer 1

Try @ManyToMany relationship using @JoinTable. A customer has a set (or a list) of products. A product has a set (or a list) of customers.

@Entity
public class Customer {
    @ManyToMany(cascade= CascadeType.ALL)
    @JoinTable(name="customer_product",
               joinColumns={@JoinColumn(name="customer_id")},
               inverseJoinColumns={@JoinColumn(name="product_id")})
    private Set<Product> products = new HashSet<Product>();
    ...

@Entity
public class Product {
    @ManyToMany
    @JoinTable(name="customer_product",
               joinColumns={@JoinColumn(name="product_id")},
               inverseJoinColumns={@JoinColumn(name="customer_id")})
    private Set<Customer> customers = new HashSet<Customer>();
    ...