The ActionSupport class implements the Validatable and ValidationAware interface and some other interface then inherit the functionality of these interface.

 
The application developer extends ActionSupport class then inherits the all functionality of Validatable ,ValidationAware ,Action and TextProvider interface.
 
TextProvider:- The TextProvider interface provides methods for obtaining values of properties file as well as methods of loading locale specific properties file.It is used in I18N
 
Action:-The Action interface doesn’t contain any method. It defines only some static final String constants name as
 SUCCESS
 FAILURE
 INPUT
 ERROR
Which can be used in action for standard coding.