JSP.8.3 Semantics of Tag Files
For each attribute declared and specified, a page-scoped variable must be created in the page scope of the
JSP Context Wrapper. The name of the variable must be the same as the declared attribute name. The value of the variable must be the value of the attribute passed in during invocation. For each attribute declared as optional and not specified, no page-scoped variable is created. If the tag accepts dynamic attributes, then the names and values of those dynamic attributes must be exposed to the tag file as specified in Table JSP.8-2.