Another parent/child problem ...

gubrak · **Joined:** Tue Mar 20, 2007 5:13 am **Posts:** 9

Hi, I just started to learn hibernate and I found problem regarding parent/child with hibernate.

I have 2 tables, Employee & Department where [Department] has one to many [Employee]

Department.hbm.xml

Code:

<class name="Department" table="DEPARTMENT">
   
        <id name="departmentId" column="DEPARTMENT_ID" type="integer" unsaved-value="0">
            <generator class="identity"/>
        </id>
        
        <property name="departmentName"   column="DEPARTMENT_NAME" 
                    type="string"
                    length="30"
                    not-null="true"/>

        <set name="employee" cascade="all">
           <key column="DEPARTMENT_ID"/>
           <one-to-many class="Employee" />
        </set>

</class>

Employee.hbm.xml

Code:

<class name="Employee" table="EMPLOYEE">
   
        <id name="employeeUserName" column="EMPLOYEE_USERNAME" type="string" length = "50">
            <generator class="assigned"/>
        </id>
        
        <property name="employeeFName"    column="EMPLOYEE_FIRSTNAME" 
                    type="string"
                    length="50"/>
        
        <property name="employeeLName"    column="EMPLOYEE_LASTNAME" 
                    type="string"
                    length="50"
                    not-null="true"/>
        
        <property name="employeePassword" column="EMPLOYEE_PASSWORD" 
                    type="string"
                    length="10"
                    not-null="true"/>
             
</class>

I have an object class for both [Department] and [Employee] and I have no problem adding department and employee to table together by using this following code:

Code:

Employee emp = new Employee("John", "Doe", bla bla);
Department dept = new Department("DeptName");
dept.addEmployee(emp);

session.save(dept);

But later in my program i want to have some ability to let me add employee without accessing Department class. Maybe by doing something like below..

Code:

Employee emp = new Employee("John", "Doe", bla bla);
emp.setDepartmentId(4);

session.save(emp);

If I want to do something like that, How should I update my hibernate xml file?

of if I can't do like what i wish to do, How is the best way to handle this problem without pulling out the Department Object again?

Thanks a lot for any help.

Jikes2005 · **Posted:** Tue Mar 20, 2007 6:26 am

Hi,

You need to have access to the department object to set the employee object. So, the code for inserting an Employee will be as follows:

Code:

Employee emp = new Employee("John", "Doe", bla bla); 
emp.setDepartment(departmentObject); 
session.save(emp); 

Hibernate will pick up the foreign key ID from the department object set on the employee object.

Jikes2005 · **Posted:** Tue Mar 20, 2007 6:29 am

Hi,

You can set the employee by using the parent Department object. Following code can be of help.

Code:

Employee emp = new Employee("John", "Doe", bla bla); 
emp.setDepartment(departmentObject); 
session.save(emp); 

As you can see, we're providing the departmentObject for hibernate to resolve the foreign key relation from employee to department.

gubrak · **Joined:** Tue Mar 20, 2007 5:13 am **Posts:** 9

Jikes2005 wrote:

Hi,

You can set the employee by using the parent Department object. Following code can be of help.

Code:

Employee emp = new Employee("John", "Doe", bla bla); 
emp.setDepartment(departmentObject); 
session.save(emp); 

As you can see, we're providing the departmentObject for hibernate to resolve the foreign key relation from employee to department.

Hi Jikes,

That is what I want from my code, but I don't really know what I need to add to my Employee.hbm.xml code to achieve that.

I assume I only need to add these following line to my Employee POJO

Code:

private Set Department = new HashSet()

public Set getDepartment(){ ... }
public void setDepartment(Set dept){ ... }

could anyone please help me on what should I add to my Employee.hbm.xml?

Thanks for any reply.

Jikes2005 · **Posted:** Wed Mar 21, 2007 8:54 am

Hi,

You need to modify your Employee mapping as below:

Code:

<class name="Employee" table="EMPLOYEE"> 
    
        <id name="employeeUserName" column="EMPLOYEE_USERNAME" type="string" length = "50"> 
            <generator class="assigned"/> 
        </id> 
        
        <property name="employeeFName"    column="EMPLOYEE_FIRSTNAME" 
                    type="string" 
                    length="50"/> 
        
        <property name="employeeLName"    column="EMPLOYEE_LASTNAME" 
                    type="string" 
                    length="50" 
                    not-null="true"/> 
        
        <property name="employeePassword" column="EMPLOYEE_PASSWORD" 
                    type="string" 
                    length="10" 
                    not-null="true"/>               

        <many-to-one name="department" column="DEPARTMENT_ID" not-null="true" />
</class> 

This tells that employee has a many-to-one relationsgip with Department. Your POJO isn't entirely correct. You'r Employee pojo should look like:

Code:

private Department department;
public Department getDepartment(){ return department; } 
public void setDepartment(Department dept){ this.department = dept; } 

This is so that an employee belongs to one department, while a department will have an HashSet of employees.

gubrak · **Joined:** Tue Mar 20, 2007 5:13 am **Posts:** 9

thanks for your help. It works perfectly!

just another note for whoever might face a same problem...

My many-to-one is as follow:

Code:

<many-to-one name="departmentId" column="DEPARTMENT_ID"
                                        class="Department"
                                        not-null="true" />