Update a child class entity from parent class using OnetoMany relationship

Question

I have Employee class and Qualification class , I added qualifications of a employee successfully. But ,When i try to update the particular employees qualification by adding one more qualification. I don't have a idea to do.Kindly suggest some view

Employee class

@Entity
@Table(name = "Tbl_Employee")
public class Employee {

private int empId;
private String empName;
private Employee_Address addressDetail;
private List<Employee_Qualification> qualifications;

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name="EmployeeId", updatable = false, nullable = false)
public int getEmpId() {
    return empId;
}
public void setEmpId(int empId) {
    this.empId = empId;
}


@Column(name="EmployeeName")
public String getEmpName() {
    return empName;
}
public void setEmpName(String empName) {
    this.empName = empName;
}


@OneToOne(cascade=CascadeType.ALL, fetch=FetchType.EAGER)
@JoinColumn(name="EmpAdd_FK")
public Employee_Address getAddressDetail() {
    return addressDetail;
}
public void setAddressDetail(Employee_Address addressDetail) {
    this.addressDetail = addressDetail;
}


@OneToMany(targetEntity=Employee_Qualification.class, mappedBy="employee"
        ,cascade=CascadeType.ALL, fetch=FetchType.LAZY)
public List<Employee_Qualification> getQualifications() {
    return qualifications;
}
public void setQualifications(List<Employee_Qualification> qualifications) {
    this.qualifications = qualifications;
}
}

Qualification class

@Entity
@Table (name="Tbl_Employee_Qualification")
public class Employee_Qualification {

private int qualificationId;
private String qualification;
private Employee employee;

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name="QualificationId", updatable = false, nullable = false)
public int getQualificationId() {
    return qualificationId;
}
public void setQualificationId(int qualificationId) {
    this.qualificationId = qualificationId;
}

@Column(name="Qualifications")
public String getQualification() {
    return qualification;
}
public void setQualification(String qualification) {
    this.qualification = qualification;
}

@ManyToOne(cascade=CascadeType.ALL, fetch=FetchType.EAGER)
@JoinColumn(name="Emp_FK")
public Employee getEmployee() {
    return employee;
}
public void setEmployee(Employee employee) {
    this.employee = employee;
}
}

Implementation class

     //      Update Employee and Employee_Qualification from Employee entity class [OnetoManny and ManytoOne bidirectional]   
     Employee emp =(Employee) session.createQuery("from Employee where empId='10'").uniqueResult();
    Employee_Qualification  newQ1  = new Employee_Qualification();
    newQ1.setQualification("ECE");

    List<Employee_Qualification> q1 = emp.getQualifications(); 
    q1.add(newQ1);

    emp.setQualifications(q1);
    session.save(q1);
    session.getTransaction().commit();

Answer 1

When you have a bidirectional relation you need to wire up both sides. In your example you already have this:

q1.add(newQ1);

but you also need to do the reverse binding too:

newQ1.setEmployee(emp)

Just a note : You have Cascade.ALL to both relations (oneToMany and ManyToOne) between your employee and qualification. I haven' t run your code but i am pretty sure is going to create an issue. You have to decide which entity is responsible to update the other. (i,e if you choose to save the qualifications and the changes to be propagated to employee then remove the cascade from the @oneToMany in the Employee class