Personally, I have a bit of trouble with Rawls's idea because the whole idea of social justice seems really difficult to me. I think that the first part of his two part test is fine. To me, that really is what justice is about -- making sure that everyone is treated equally in the eyes of the law.
But when you start getting into ideas of making sure that the social and economic inequalities are arranged right, I think justice becomes impossible to define.
For example, what level of economic equality does each member of our society deserve to have? How do you determine how much economic inequality is enough and how much is too much? I don't see any way to actually answer that.
So my answer is that justice is making sure people are treated equally in the eyes of the law.