Parse a custom tag using request information in JSP

Question

I have a simple problem but I haven't had any luck finding the solution with Google.

I want to expand custom JSP tags but I want to be able to parse it differently depending on request information. For example the tag:

<my:tag type="..."/>

Should be expanded differently if the parameters in the request differ:

http://localhost:8080/context/servlet?arg=web

Should yield a different result than:

http://localhost:8080/context/servlet?arg=mobile

Does anybody know how the tag parsing class (usually expands TagSupport) can access or be passed parameters from the request?

Answer 1

Inside the tag class, you can access the request object and get the parameter by

this.pageContext.getRequest().getParameter("arg");

Answer 2

You can access it through the getParameter() method of HttpServletRequest object.

String arg1 = request.getParameter("arg");

There, you have the variable arg1 that contains "web" or "mobile" when hit from different URL as in your 2 examples.

Answer 3

You could use the Expression Language to supply the request parameter to your JSP-Tag.

<my:tag type="${param.arg}"/>