In the use of struts2 tags, when to use # and when not to use #

The objects in the value stack are not used#, the objects in the non-value stack are used# 
If you don't understand the function of the value stack, simply understand: the current action, or the attribute of the action in the action chain, and it is the attribute Provide getter and setter methods, then you don't need to use # in jsp, and you need to use #, then from here you can know the properties of action If you provide getter and setter methods, then these property values ​​will be placed to the value stack