Consider a concrete parent class (Employee) and an inherited class (ContractEmployee) that roughly mirrors my specific issue (Ideally, Employee should be abstract, ..but using Employee as a concrete parent class mirrors my situation more closely).
The annotations follow (using a mixed inheritance strategy)
Code:
@Entity
@Table(name = "EMPLOYEE")
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
public class Employee {
@Id
@Column(name = "ID")
@GeneratedValue
private long id;
@Column(name = "NAME")
private String name;
@Column(name = "ADDRESS")
private String address;
...
}
Code:
@Entity
@DiscriminatorValue("CE")
@SecondaryTable(name = "CONTRACT_EMPLOYEE",
pkJoinColumns = @PrimaryKeyJoinColumn(name = "CONTRACT_EMPLOYEE_ID")
)
public class ContractEmployee extends Employee{
@Column(table = "CONTRACT_EMPLOYEE",
name = "CE_HOURLYRATE",
nullable = false
)
private int hourlyRate;
...
}
In the DB, this is what I see.
Code:
mysql> select * from employee;
+----------+----+------------------------+----------+
| DTYPE | ID | ADDRESS | NAME |
+----------+----+------------------------+----------+
| Employee | 1 | 11 wide open road | emp joe |
| CE | 2 | 1 some street | ctr jack |
+----------+----+------------------------+----------+
mysql> select * from contract_employee;
+---------------+----------------------+
| CE_HOURLYRATE | CONTRACT_EMPLOYEE_ID |
+---------------+----------------------+
| 100 | 2 |
+---------------+----------------------+
1 row in set (0.00 sec)
Id 1 = Employee
Id 2 = Contractor
Question: Consider the following driver code and the results:
Code:
//1
ContractEmployee cemp = EmployeeDAO.retrieveContractEmployee(2); //HQL: from ContractEmployee where id = :id
System.out.println(cemp);
System.out.println("********************");
//2
Employee emp = EmployeeDAO.retrieveEmployee(2); //HQL: from Employee where id = :id
System.out.println(emp);
System.out.println("********************");
//3
Employee emp1 = EmployeeDAO.retrieveEmployee(1);//HQL: from Employee where id = :id
System.out.println(emp1);
Code:
Hibernate: select contractem0_.ID as ID1_, contractem0_.ADDRESS as ADDRESS1_, contractem0_.NAME as NAME1_, contractem0_1_.CE_HOURLYRATE as CE1_2_ from EMPLOYEE contractem0_ left outer join CONTRACT_EMPLOYEE contractem0_1_ on contractem0_.ID=contractem0_1_.CONTRACT_EMPLOYEE_ID where contractem0_.DTYPE='CE' and contractem0_.ID=?
com.xyz.data.ContractEmployee@1329642[name=ctr jack,hourlyRate=100,address=1 some street,id=2]
********************
Hibernate: select employee0_.ID as ID1_, employee0_.ADDRESS as ADDRESS1_, employee0_.NAME as NAME1_, employee0_1_.CE_HOURLYRATE as CE1_2_, employee0_2_.FE_HOURLYRATE as FE1_3_, employee0_.DTYPE as DTYPE1_ from EMPLOYEE employee0_ left outer join CONTRACT_EMPLOYEE employee0_1_ on employee0_.ID=employee0_1_.CONTRACT_EMPLOYEE_ID left outer join FULLTIME_EMPLOYEE employee0_2_ on employee0_.ID=employee0_2_.FULLTIME_EMPLOYEE_ID where employee0_.ID=?
com.xyz.data.ContractEmployee@15575e0[name=ctr jack,hourlyRate=100,address=1 some street,id=2]
********************
Hibernate: select employee0_.ID as ID1_, employee0_.ADDRESS as ADDRESS1_, employee0_.NAME as NAME1_, employee0_1_.CE_HOURLYRATE as CE1_2_, employee0_2_.FE_HOURLYRATE as FE1_3_, employee0_.DTYPE as DTYPE1_ from EMPLOYEE employee0_ left outer join CONTRACT_EMPLOYEE employee0_1_ on employee0_.ID=employee0_1_.CONTRACT_EMPLOYEE_ID left outer join FULLTIME_EMPLOYEE employee0_2_ on employee0_.ID=employee0_2_.FULLTIME_EMPLOYEE_ID where employee0_.ID=?
com.xyz.data.Employee@81b1fb[name=emp joe,address=11 wide open road road,id=1]
Cases 1 and 2 are as expected. Is there any way to execute case 3 without invoking the JOINs on the FULLTIME_EMPLOYEE + CONTRACT_EMPLOYEE tables, assuming I already know that there are no children for a particular ID (from the DTYPE column)?
Thanks
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