Hibernate Mysql映射关系

Question

I'm not sure if this is possible to do in Spring 3 framework using hibernate and mysql but I would appreciate any help. I have two classes - Employee and Examiner. The examiner is an employee and an employee is also an examiner. At the same time each Examiner can examine one or more employees and an employee can only have one Examiner.

Basically what I want to know is if it is possible to show the inheritance between the Employee and Examiner, and at the same time map a unidirectional one to many from Examiner to Employee?

What I have so far - the Examiner table with the inheritance constraint:

CREATE TABLE `examiner` (
`employee_id` varchar(255) NOT NULL,
`employee_name` varchar(255) NOT NULL,
 PRIMARY KEY (`enployee_id`),
 FOREIGN KEY (`employee_id`) REFERENCES `employee` (`employee_id`)): 

The employee table:

 CREATE TABLE `employee` (
`employee_id` varchar(255) NOT NULL,
`employee_name` varchar(255) DEFAULT NULL,
PRIMARY KEY (`employee_id`)):

I was thinking of a join table for showing the one to many behaviour but getting a compsite key for the table is not possible as I have a primarykeyjoin column.

I would appreciate any help in pulling this together as I have been stumped for days.

Answer 1

Java doesn't allow multiple inheritance, so unless you are using an interface I am not sure how you plan to make the two described classes instances of each other.

You could just make a class called EmployeeExaminer, and make it reference itself. With annotations it might look something like:

@Entity
public class EmployeeExaminer {
  @ManyToOne
  private EmployeeExaminer getExaminer() {/*...*/}

  @OneToMany
  private List<EmployeeExaminer> getEmployees() { /*...*/}
}

Documentation on the annotations can be found here .

Answer 2

Thanks @CodeChimp for your replies. I ended up following the first suggestion, and created a Self Reference class with the @onetomany and @manytoone annotations. The helper class for it works. I just have some problems implementing a controller and jsp page for adding the parent/child. But I will make a new question for that. Thanks again.