Consider Developing a Tag Library Validator
To
make the page author’s life as easy as possible, you
should consider implementing a tag library validator for your custom
tag library. This type of validator was introduced in JSP 1.2, and it
can do a much better job verifying that all custom actions are used
correctly than the previous mechanism (the
TagExtraInfo
class) could.
You implement a tag library validator by extending
javax.servlet.jsp.tagext.TagLibraryValidator
and provide an implementation for the abstract validate( )
method:
public ValidationMessage[ ] validate(String prefix, String uri, PageData pd)
The container calls this method when it translates the page into a
servlet. The parameters provide the validator with the tag library
prefix, URI (declared by the taglib directive in
the page), and, most importantly, a PageData
instance. Through the PageData instance, the
validator gains access to an XML representation of the complete page
(called an XML view). With access to the full
page in a format that’s easy to parse, it can make
sure the actions are properly nested and appear in the right order,
in addition to what’s always been possible: checking
the proper use of all attributes for each individual custom action
element.
The validate( ) method returns an array of
ValidationMessage objects. Each object represents a validation error, containing a text message plus a unique element ID that the container can use to map the error message to the location of the corresponding ...