ONE - ONE Bidirectional ? < ------ >
ONE - ONE Unidirectional ? --------->
Here is my understanding:
Suppose there are two beans A and B.
Bidirectional means: A can get B, and B can get A too;
In A: getB();
In B: getA();
Unidirectional means: A can get B, but B can't get A.
In A: getB();
In B: no method to get A.