Using the expression language, you can directly obtain the request parameter value, obtain the specified attribute value of the JavaBean in the page, obtain the request header and obtain the attribute value of the page, request, session and application scope, etc., all of which benefit from the built-in object of the expression language. .
The Expression Language contains 11 built-in objects as follows.
- pageContext: The pageContext object representing the page, which is the same as the JSP's pageContext built-in object.
- pageScope: The property value used to get the page scope.
- requestScope: The attribute value used to obtain the request scope.
- sessionScope: The attribute value used to obtain the session scope.
- applicationScope: used to get the property value of the application scope.
- param: The parameter value used to get the request.
- paramValues: used to obtain the parameter values of the request. The difference from param is that this object is used to obtain the attribute value of the attribute value of the array.
- header: The attribute value used to get the request header.
- headerValues: used to get the property value of the request header. The difference from the header is that this object is used to get the property value of the property value as an array.
- initParam: used to obtain the initialization parameters of the requesting web application.
- cookie: used to get the specified cookie value.