One of the major usages of <io:request> is to get around the limitations imposed by the <jsp:include> tag that limits the developer to including only contents of the same web application. According to the documentation of <io:request>, " The URL to request. If the URL starts with '/' then it is treated as a local http request " However, the behavior of URLHelper.createURL(String uri, PageContext pageContext) is inconsistent with this because it automatically includes the context path in the resulting URL if the request in the associated PageContext is an instance of HttpServletRequest (the ordinary case with a JSP.) This means that <io:request> cannot be used to relatively link to a document in another web application running on the same server. Since <jsp:include> already provides the capability to include a document from the same web application, and in a less roundabout fashion, I strongly recommend and request that the logic be altered to ignore the context and treat paths starting with "/" as beginning at the server root, as the documentation specifies. If the user then desires to use <io:request> to obtain a resource from the same web application, it is trivial for them to either manually concatenate the context name to the requested URL, or to simply use a <jsp:include> tag.
Resolving. Taglib has been retired.