logic:notPresent

Generate the nested body content of this tag if the specified value is not present in this request.

Depending on which attribute is specified, this tag checks the current request, and evaluates the nested body content of this tag only if the specified value is not present. Only one of the attributes may be used in one occurrence of this tag, unless you use the property attribute, in which case the name attribute is also required.

Can contain: JSP

Attributes

Name	Description	Type
cookie	Checks for the existence of a cookie with the specified name.	String
header	Checks for the existence of an HTTP header with the specified name. The name match is performed in a case insensitive manner.	String
name	Checks for the existence of a JSP bean, in any scope, with the specified name. If property is also specified, checks for a non-null property value for the specified property.	String
parameter	Checks for the existence of at least one occurrence of the specified request parameter on this request, even if the parameter value is a zero-length string.	String
property	Checks for the existence of a non-null property value, returned by a property getter method on the JSP bean (in any scope) that is specified by the name attribute. Property references can be simple, nested, and/or indexed.	String
role	Checks whether the currently authenticated user (if any) has been associated with the specified security role.	String
scope	The bean scope within which to search for the bean named by the name property, or "any scope" if not specified.	String
user	Checks whether the currently authenticated user principal has the specified name.

 

 

1.3官方例子

ERROR: Application resources not loaded -- check servlet container logs for error messages.

 

当name中的类实例不存在任何范围中时候，会显示标签里的内容。