Hello All
This post is about various usage of view link accessor , when we create viewLink between two viewObjects , destination accessor is created by default in master viewObject, there is check box to create source accessor also at same time
We can use this view link accessor for calculating attribute's sum, setting value of attributes etc
here Departments is master viewObject and Employees is it's detail, after creating viewLink you can see in viewObject xml source there accessor is present
In Departments ViewObject-
<ViewLinkAccessor
Name="Employees"
ViewLink="sample.model.view.link.DeptTOEmpVL"
Type="oracle.jbo.RowIterator"
IsUpdateable="false"/>
In EmployeesViewObject-
<ViewLinkAccessor
Name="Departments"
ViewLink="sample.model.view.link.DeptTOEmpVL"
Type="oracle.jbo.Row"
Reversed="true"
IsUpdateable="false"/>
So what is the use of these view link accessors ?
Master accessor in detail viewObject returns current Row of master viewObject, when you generate RowImpl class for detail viewObject , it also has a method for this accessor
/**
* Gets the associated <code>Row</code> using master-detail link Departments.
*/
public Row getDepartments() {
return (Row) getAttributeInternal(DEPARTMENTS);
}
/**
* Sets the master-detail link Departments between this object and <code>value</code>.
*/
public void setDepartments(Row value) {
setAttributeInternal(DEPARTMENTS, value);
}
Detail accessor in master viewObject returns a row set of all row of details viewObject that are currently referenced by master record
/**
* Gets the associated <code>RowIterator</code> using master-detail link Employees.
*/
public RowIterator getEmployees() {
return (RowIterator) getAttributeInternal(EMPLOYEES);
}
Now see what we can do with viewLink Accessor
1. Get master attribute value in detail viewObject
suppose i have to get a attribute's value from Master viewObject (Departments) in a attribute of detail viewObject (Employee)
in this example i am getting managerId from Departments ViewObject so for this just write in expression of Employee's ManagerId field
viewLinkAccesorName.AttributeName
now run BC4J tester and check - create new record in Employee and see managerId from Departments is auto populated
on creating new record-
2. Call aggregate function to calculate sum of an attribute of detail viewObject
suppose now i have to calculate total salary of a Department (sum of Employees salary of that department)
for this purpose just call sum function to calculate sum of all rows of detail RowSet
take a transient attribute in Departments ViewObject and write in it's expression
viewLinkAccesorName.sum("AttributeName")
Run ApplicationModule and see-
3. Set bind variable value as per master viewObject's attribute (pass value from master viewObject)
This is tricky part as we can not set bind variable value through expression as it doesn't recognize view link accessor name.
created a viewCriteria and bind variable for managerId in Employee viewObject
applied this criteria to Employees viewObject instance in Application Module (Just Shuttle criteria to selected side)
now to set bind variable's value we have to override
prepareRowSetForQuery method in Employees VOImpl class
this method gets the value of managerId from currentRow of master ViewObject (Departments)and sets in bind variable of Employees viewObject
@Override
public void prepareRowSetForQuery(ViewRowSetImpl viewRowSetImpl) {
RowSetIterator[] masterRows = viewRowSetImpl.getMasterRowSetIterators();
if (masterRows != null && masterRows.length > 0 && masterRows[0].getCurrentRow() != null &&
masterRows[0].getCurrentRow().getAttribute("ManagerId") != null) {
Integer managerId = (Integer) masterRows[0].getCurrentRow().getAttribute("ManagerId");
viewRowSetImpl.ensureVariableManager().setVariableValue("BindManagerId", managerId);
System.out.println("ManagerID in bind Var-" + managerId);
}
super.prepareRowSetForQuery(viewRowSetImpl);
}
now run AM and check it-
Happy Learning :)
Output-
