Difference between Struts 1 and Struts 2

Struts1 extends the abstract base class by its action class. The problem with struts1 is that it uses the abstract classes rather than interfaces. 

While in Struts 2, an Action class implements an Action interface, along with other interfaces use optional and custom services. Struts 2 provides a base ActionSupport class that implements commonly used interfaces. Although an Action interface is not necessary, any POJO object along with an execute signature can be used as an Struts 2 Action object.