java JPA/toplink异构实体列表

Question

各位同事:， 使用JPA，我需要解决以下问题：在数据库级别存在3个实体（表示SuperEntity、DetailsAgentity和DetailsByEntity）。SuperEntity包含DetailsAgentity和DetailsAgentity字段的公共部分

所以问题是：是否有可能从JPA中解决混合元素detailsAgentity和detailsEntity的集合？是否可以在toplink中退出某些扩展以指定实体的类

Answer 1

在标准JPA中，查询是多态的。以下是JPA 1.0规范中的相关章节：

3.6.5 Polymorphic Queries

By default, all queries are polymorphic. That is, the FROM clause of a query designates not only instances of the specific entity class(es) to which it explicitly refers, but subclasses as well. The instances returned by a query include instances of the subclasses that satisfy the query conditions.

For example, the query

select avg(e.salary) from Employee e where e.salary > 80000

returns the average salary of all employees, including subtypes of Employee, such as Manager and Exempt.

及

4.4.8 Polymorphism

Java Persistence queries are automatically polymorphic. The FROM clause of a query designates not only instances of the specific entity class(es) to which explicitly refers but of subclasses as well. The instances returned by a query include instances of the subclasses that satisfy the query criteria.

因此，默认情况下，对超类型的任何查询都会在结果中包含子类型

Answer 2

假设SuperEntity被映射为继承树的根，那么该类型的查询结果可以返回其具体子类的异构集合