JPA Entity with hierachy relationship - sql

Question

I have the following Entity
#Entity
public class Project implements Serializable {
#Id
private Integer project_id;
private String project_name;
other attributes
#OneToOne
#JoinColumn(name = "lead_emp_no", referencedColumnName = "emp_no")
private Employee projectLead;
// but the following two relationships need to be a connect by:
#OneToOne
#JoinColumn(name = "lead_boss_emp_no", referencedColumnName = "emp_no")
private Employee projectLeadBoss;
#OneToOne
#JoinColumn(name = "lead_bosses_boss_emp_no", referencedColumnName = "emp_no")
private Employee projectLeadBossesBoss;
With this setup, we have to manually maintain the employee numbers for the Lead's boss and the Lead's Boss's boss. This relationship is [somewhat] already available knowing the projectLead employee:
The Employee Entity is as follows:
#Entity
public class Employee implements Serializable {
#Id
private Integer emp_no;
private Integer bosses_emp_no;
Is it possible to get my Project entity to connect to the boss and bosses Employee based on projectLead? In single query I'd like to get a table of all projects and their lead's hierarchy. I'm open to entity redesign.

Answer 1

You can replace the bosses_emp_no in Employee should with a more helpful boss:
#Entity
public class Employee implements Serializable {
#Id
private Integer emp_no;
#OneToOne
#JoinColumn(name = "boss_emp_no", referencedColumnName = "emp_no")
private Employee boss;
Then you simply add a couple of delegating methods to Project
public Employee getProjectLeadBoss() {
return this.projectLead.getBoss();
}
public Employee getProjectLeadBossesBoss() {
return this.getProjectLeadBoss().getBoss();
}