I got into an interesting internet argument about getter and setter methods and encapsulation. Someone said that all they should do is an assignment (setters) or a variable access (getters) to keep them "pure" and ensure encapsulation.

• Am I right that this would completely defeat the purpose of having getters and setters in the first place and validation and other logic (without strange side-effects of course) should be allowed?
• When should validation happen?
  • When setting the value, inside the setter (to protect the object from ever entering an invalid state - my opinion)
  • Before setting the value, outside the setter
  • Inside the object, before each time the value is used
• Is a setter allowed to change the value (maybe convert a valid value to some canonical internal representation)?