Hibernate 分组和结果集转换

Question

假设我有以下结果集：

所以，我们这里是一对多对多的关系。 问题是在 Hibernate 中对它进行分组并将此数据结构转换为具有以下字段的 DTO 的最佳方法是：

String countryName String companyName List invoiceNumbers

谢谢！

Answer 1

对于Country 和Company ---- Many-to-Many 对于公司和发票 --- One-to-Many

@Entity
public class Country {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private Long id;

@ManyToMany(mappedBy="countries")
private Collection<Country> countries;
...
getters and setters

}

@Entity
public class Company {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private Long id;

@ManyToMany
private Collection<Country> countries;

@OneToMany
private Collection<Invoice> invoices; 
...
getters and setters

}

@Entity
public class Invoice {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private Long id;

private int invoice_number;
...
getters and setters

}