EJB3.0 entities and relationships
Hello all!
I'm developing a timesheet application. It consists of charges and employees. Charges can be either work charges or expense charges. Employee can have many work charges and/or expense charges but each charge belongs only to a single employee.
I have developed EJB3.0 entities for employee, charge, work charge and expense charge. Charge is a superclass for both WorkCharge and ExpenseCharge. When I deploy these entities to the container new tables are created in the database. However, when I inspect these tables I find that both WORK_CHARGE and EXPENSE_CHARGE tables have a foreign key column for employee although I expect only the CHARGE table to have a foreign key column to EMPLOYEE table.
Below is a code for entities. I would be grateful if someone could help me determine where I'm making mistake. Thank you in advance.
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/* Charge entity is superclass for both WorkCharge and ExpenseCharge
entities. It must be abstract as charges can be either work or expense
*/
package hr.ursic.timesheetEJB;
import java.util.*;
import javax.persistence.*;
@Entity
@Table(name="CHARGE")
@Inheritance(strategy=InheritanceType.JOINED)
public abstract class Charge {
protected Long id;
protected Date date;
protected Employee employee;
// accessor methods for work charge id
@Id (generate=GeneratorType.AUTO)
@Column (name="ID")
public Long getId(){
return id;
}
public void setId(Long id){
this.id = id;
}
// accessor methods for work charge date
@Column (name="CHARGE_DATE")
public Date getDate(){
return this.date;
}
public void setDate(Date date){
this.date = date;
}
// accessor methods for employee
@ManyToOne
@JoinColumn (name="EMPLOYEE")
public Employee getEmployee(){
return employee;
}
public void setEmployee(Employee employee){
this.employee = employee;
}
}
/* WorkCharge entity represents work charges */
package hr.ursic.timesheetEJB;
import javax.persistence.*;
@Entity
@Table(name="WORK_CHARGE")
public class WorkCharge extends Charge {
private Double time;
// accessor methods for work charge time
@Column (name="CHARGE_TIME")
public Double getTime(){
return time;
}
public void setTime(Double time){
this.time = time;
}
// retrieve work charge details
@Transient
public WorkChargeDetail getDetails(){
WorkChargeDetail workChargeDetail = new WorkChargeDetail();
workChargeDetail.setEmployeeId(getEmployee().getId());
workChargeDetail.setDate(this.getDate());
return workChargeDetail;
}
}
/* Employee entity represents employees */
package hr.ursic.timesheetEJB;
import java.util.*;
import javax.persistence.*;
@Entity
@Table(name = "EMPLOYEE")
public class Employee {
private Long id;
private Collection workCharges;
private Collection expenseCharges;
// accessor methods for employee id
@Id (generate = GeneratorType.AUTO)
@Column (name = "ID")
public Long getId(){
return id;
}
public void setId(Long id){
this.id = id;
}
// accessor methods for work charges
@OneToMany (cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy = "employee")
public Collection getWorkCharges(){
return workCharges;
}
public void setWorkCharges(Collection workCharges){
this.workCharges = workCharges;
}
// accessor methods for expense charges
@OneToMany (cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy = "employee")
public Collection getExpenseCharges(){
return expenseCharges;
}
public void setExpenseCharges(Collection expenseCharges){
this.expenseCharges = expenseCharges;
}
}