how to check the call is from the which specific child controller? - spring

Question

I have two controller classes extending basecontroller. I have a common functionality to be implemented and implementation is in basecontroller.
public class BaseController{
protected void populateWidget(List li, int zipcode){
//implementation for child A
populate only 10 employee records
//implementation specific to child B
populate 100 student records
}
}
public class ChildA extends BaseController{
List<Employees> li = ...
populateWidget(li, 90034)
}
public class ChildB extends BaseController{
List<Students> li = ...
populateWidget(li, 90034)
}
I have written setChildB method and working on it. like below
public class BaseController{
protected boolean childB;
protected void setIsChildB(boolean childB){ this.childB = childB;}
protect boolean isChildB(){ return childB; }
protected void populateWidget(List li, int zipcode){
//implementation for child A
if(!isChildB())
populate only 10 employee records
else
//implementation specific to child B
populate 100 student records
}
}
public class ChildA extends BaseController{
List<Employees> li = ...
populateWidget(li, 90034)
}
public class ChildB extends BaseController{
List<Students> li = ...
setChildB(true); //setting as child B call
populateWidget(li, 90034)
}
Please advice the best way to do it.

Answer 1

I recommend implementing a Template Method Pattern. You could have your base controller like this:
public class BaseController {
protected abstract void getPeople(List li, int zipcode);
protected void populateWidget(List li, int zipcode) {
//Do generic logic here
//Refer to child
getPeople(List li, int zipcode)
//Do some more generic stuff
}
}
And then each of your children like this:
public class ChildA extends BaseController {
#Override
protected void getPeople(List li, int zipcode) {
//Specific Logic here
}
}
The children each override the getPeople() method to do their own thing.
That way if you need a ChildC, you can simply extend the parent without changing it.
Update: Based on the comments, here is an alternative way of doing this.
I would not do it as a setter, rather I would make a constructor argument on the base class that takes the type of child as an argument. This makes sure that the compiler enforces that you will always have a value set
You could use a boolean but I recommend strongly using an Enum, String constant or int constant.
The above two points are mostly because I always anticipate that I might have to do a ChildC when some requirements change comes along and at that point you won't have to do changes to the base class. It also falls into the set of patterns that other programmers I work with would expect and therefore makes the code easier readable and maintainable by others.
Sample base class:
public class BaseController {
private int childType;
protected static final int CHILD_A = 1;
protected static final int CHILD_B = 2;
public BaseController(int aChildType) {
childType = aChildType;
}
protected void populateWidget(List li, int zipcode) {
switch (childType) {
case CHILD_A:
//Handle Child A
case CHILD_B:
//Handle Child B
}
}
}
The child implementation would look like this:
public class ChildA extends BaseController {
public ChildA () {
super(CHILD_A);
}
//The rest of your code goes here...
}
Note, that in the above example I am using integer constants for the sake of brevity. In the 21s century Java creating an Enum would be the preferred way to go.