ManyToMany inverseJoinColumns side null fields

[Sharmila Punde]

Dear All,
Database table structure is as -

create table office_branch(branch_id integer PRIMARY KEY, branch_name varchar(20));
create table employee(employee_id integer PRIMARY KEY, employee_name varchar(20));

create table office_branch_employee(obe_branch_id integer, obe_employee_id integer, 
constraint branchIdFk FOREIGN KEY(obe_branch_id) references office_branch(branch_id), 
constraint employeeIdFk FOREIGN KEY(obe_employee_id) references employee(employee_id));

Please take a look at code which works fine -

@Entity
@Table(name="office_branch")
public class OfficeBranch implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @Column(name="branch_id")
    private int branchId;

    @Column(name="branch_name")
    private String branchName;

	//get and set methods for branchId , branchName

    @ManyToMany(cascade=CascadeType.ALL)
    @JoinTable(name="office_branch_employee",
        joinColumns=
            @JoinColumn(name="obe_branch_id", referencedColumnName="branch_id"),
        inverseJoinColumns=
            @JoinColumn(name="obe_employee_id", referencedColumnName="employee_id"))
    private Vector<Employee> employees;

	//get and set methods for employees
	//hashCode, equals, to String methods
}

@Entity
@Table(name="employee")
public class Employee implements Serializable {
    
    private static final long serialVersionUID = 1L;

    @Id
    @Column(name="employee_id")
    protected int employeeId;

    @Column(name="employee_name")
    protected String employeeName;

    //get and set methods for employeeId, employeeName

    @ManyToMany(mappedBy="employees", cascade=CascadeType.ALL)
    private Vector<OfficeBranch> officeBranches;
    //get and set methods for officeBranches
    //hashCode, equals, to String methods
}

Piece of code to persist entity OffficeBranch as -
OfficeBranch ob = new OfficeBranch();
ob.setBranchId(new Integer(branchId));
ob.setBranchName(branchName);

Vector<Employee> emps = new Vector<Employee>();
Employee e1 = new Employee();
e1.setEmployeeId(new Integer(employeeId1));
e1.setEmployeeName(employeeName1);
emps.add(e1);
            
Employee e2 = new Employee();
e2.setEmployeeId(new Integer(employeeId2));
e2.setEmployeeName(employeeName2);
emps.add(e2);

ob.setEmployees(emps);

en.persist(ob); // where en is entity manager
en.flush();
en.refresh(ob); //#0

OfficeBranch retrievedBranch = ob;

Vector allEmployees = retrievedBranch.getEmployees();
System.out.println("OfficeBranch to Employees "+allEmployees+"<br>"); //#1
Iterator<Employee> ite = allEmployees.iterator();
while(ite.hasNext()) {
        Employee empNest = ite.next();
        Vector<OfficeBranch> empsOfficeBranches = empNest.getOfficeBranches(); //#2
        for(int i = 0; i < empsOfficeBranches.size(); i++) {
             OfficeBranch b = empsOfficeBranches.get(i);
             System.out.println("Employee to Office "+b.getBranchId()+"="+b.getBranchName()+"<br>");
         }
}

I can see output of line #1 with list of 2 employees,
But somehow persistence provider do not initialize Employee.officeBranches , so the 'empsOfficeBranches'
on line #2 get initialized to null.
What is the problem with the above code? Why Employee.officeBranches does not get initialized
with list of OfficeBranch after en.refresh(ob) method call on line #0.

Thanks

[Will Myers]

Try adding fetch=FetchType.EAGER to the @ManyToMany annotations, the default is Lazy I think