$, %, #, {}, ^, And $ tags in OGNL

Use of $ in OGNL 1 .. in the international resource file, reference OGNL expression 2 .. in struts. in the xml file, reference the use of the "%" sign in the OGNL expression OGNL 1 .. you can use % {} to retrieve the Action object stored in the value stack and directly call its method 2 .. if Action inherits ActionSupport, you can use % {getText ('key')} In the page tag ')} get International Information # In OGNL use # In OGNL to retrieve the name of the object stored in the stack context. Example: attr is used to access its attributes in the order of request> session> application # attr. userName is equivalent to reading the userName attribute from three ranges until the request contains the Map # request of the attribute of the current HttpServletRequest. userName is equivalent to request. getAttribute ("userName") sessio N Map # session that contains the attributes of the current HttpSession. userName is equivalent to session. getAttribute ("userName") application contains the Map of the attributes of the current application's ServletContext # application. userName is equivalent to application. getAttribute ("userName") parameters contains the Map # parameters of the current HTTP request parameter. id [0] is equivalent to request. when getParameter ("id") uses projection to obtain attributes and uses projection to obtain the username attribute of objects in the List, {} indicates a collection of stus. {username} indicates that it is flexible to retrieve all the username attributes of suts and form a new list using the OGNL expression to obtain the attributes selected, you can use both the selection technology and projection technology to obtain attributes. When you use the selection technology, # t His indicates the current element. question mark? All elements that meet the conditions are obtained. The up arrow ^ indicates the beginning, that is, the first data in the Qualified Data Index, so stus. {^ # this. grade> = 60 }. {username} outputs [zhangsan] note that the output text contains brackets, which indicates that it is a list. And stus .{? # This. grade> = 60}. {username} [0] output is a string, which is different. The dollar sign $ indicates the end, that is, take the last row of data in the Qualified Data Index, so stus. {$ # this. grade> = 60 }. {username} outputs the [Wang Wu] symbols: Question mark, top arrow, and dollar sign all return List