What are <required> and <rtexprvalue> used for?-Collection of common programming errors

The “rtexprvalue” element defined in a TLD is captures the dynamic behavior of an attribute. The value can be either true or false. A false value in the dynamic column means that only a static string value can be specified for the attribute. A true value means that a request-time attribute value can be specified. As defined in the JSP specification, a “request-time attribute value” can be either a Java expression, an EL expression, or a value set by a .

The “required” defines if the nesting attribute is required or optional. If not present then the default is “false”, i.e the attribute is optional.