JSP-09-use EL to display data, jsp-09-el data

JSP-09-use EL to display data, jsp-09-el data
Objective: To make JSP writing easier. 9.1 EL expression

$ {EL expression }:: {unsername}

Operator: "." OPERATOR: attribute used to access objects $ {news. title}

"[]" OPERATOR: attribute used to access objects $ {news ["title"]}

Used to access arrays or collections $ {newslist [0]}

Note: 1. EL is case sensitive.

2. Before using EL, you must first store the object in the scope. Storing an object in the scope does not copy the object. The scope only saves the reference of the object, so it has almost no impact on the server performance.

 

9.2 EL usage

Obtain attributes of a javaBean object	$ {News. title}
Obtains elements of an array, List, or Map object.	$ {List [0]}
Simple processing of raw data using various operators	$ {TotalRecordCount/pageSize} can be computed.
Block Common exceptions	$ {Username} the username does not exist and no exception occurs.
Easy Automatic type conversion	$ {News} is equivalent to (News) request. getAttribute ("news ")

 

9.3 jsp el-defined implicit objects

PageContext	Provide access to page properties
Request	Accept the JSP page request from the client	$ {PageContext. request. contextPath}
Param	The value of a single string should be set for the return request parameter name
ParamValues	Returns the Request Parameters mapped to the client.
ParamScope	Return the variable name of the page range.
RequestScope
SessionScope
Applicationscope

 

7.4 applicable Operators

 

 

1.5 EL access scope