Use ognl expressions

<Li> common attribute of the action in the Access value Stack: username = <s: property value = "username"/> </LI> <li> access the common attributes of objects in the value stack (Get Set Method): <s: property value = "user. age "/> | <s: property value =" User ['age'] "/> | <s: property value = "User [\" Age \ "]"/> | wrong: <% -- <s: property value = "User [age]"/> -- %> </LI> <li> access the common attributes of objects in the value stack (Get Set Method): <s: property value = "cat. friend. name "/> </LI> <li> common method for accessing objects in the value Stack: <s: property value =" password. length () "/> </LI> <li> Usage: <s: property value = "cat. miaomiao () "/> </LI> <li> common method for accessing action in the value Stack: <s: property value =" m () "/> </LI> <HR/> <li> static access method: <s: property value =" @ COM. bjsxt. struts2.ognl. s @ s () "/> </LI> <li> access static properties: <s: property value =" @ COM. bjsxt. struts2.ognl. s @ Str "/> </LI> <li> static method for accessing the math class: <s: property value =" @ max) "/> </LI> <HR/> <li> constructor for accessing common classes: <s: property value =" new COM. bjsxt. struts2.ognl. user (8) "/> </LI> <HR/> <li> access list: <s: Prope Rty value = "users"/> </LI> <li> access an element in the list: <s: property value = "users [1]"/> </LI> <li> access the set of an attribute in the list element: <s: property value = "users. {age} "/> </LI> <li> access the specific value of an attribute set in the list element: <s: property value =" users. {age} [0] "/> | <s: property value =" users [0]. age "/> </LI> <li> access set: <s: property value =" dogs "/> </LI> <li> access an element in the Set: <s: property value = "Dogs [1]"/> </LI> the set cannot be obtained. <li> Access Map: <s: property value = "dogmap"/> </LI> <li> access an element in map: <s: Pr Operty value = "dogmap. dog101 "/> | <s: property value =" dogmap ['dog101 '] "/> | <s: property value = "dogmap [\" dog101 \ "]"/> </LI> <li> access all keys in map: <s: property value = "dogmap. keys "/> </LI> <li> access all values in map: <s: property value =" dogmap. values "/> </LI> <li> access container size: <s: property value =" dogmap. size () "/> | <s: property value =" users. size "/> </LI> <HR/> <li> projection (filter): <s: property value =" users. {? # This. age = 1} [0] "/> </LI> <li> projection: <s: property value =" users. {^ # This. age> 1 }. {age} "/> </LI> <li> projection: <s: property value =" users. {$ # This. age> 1 }. {age} "/> </LI> <li> projection: <s: property value =" users. {$ # This. age> 1 }. {age }== null "/> </LI> <HR/> <li> []: <s: property value =" [0]. username "/> </LI>