About the JpetStore of Spring where

amy

While i hadn't sign-in the JpetStore.But   i bought a cat,I clicked the quot;continuequot; button  on the quot;checkout.jspquot;,so told me input the userid and password.
While i sign-in the JpetStore,If i cliecked the  quot;continuequot; button on the quot;checkout.jsp quot; i can look the order information.   
   My question is i don't know the code how control quot;continuequot; button open the quot;viewOrder.jspquot; and quot;signonForm.jspquot;? And i don't know where is the code ?          Thank you!