I understand what you're trying to do, however, you've skipped the crucial steps for using TagSupport. First, you need to create a .java file that either implements or extends TagSupport. If you implement it, there are several methods you'll have to overwrite. If you extend it, you only need to overwrite the methods you'll be using. The documentation for these methods can be found
HERE. Second, in your web application,
you should have a folder called WEB-INF, which contains web.xml. In this folder, you'll need to add a .tld file, which will provide information for the custom tag. Last, in your JSP, you'll call the custom tag. In order to reference it, you'll use: <%@ taglib uri="WEB-INF/myTagLib.tld" prefix="g" %>. Later in your JSP, you'll use <g: customTag />. In your .tld, you'll define the role of customTag and call the .java. "g" is just a random letter I chose, you can use whichever letter as long as it is not one already in use. For example, if you're going to use JSTL, you shouldn't use "c" as your custom tag.
If you absolutely need to use the custom tag in an <input> tag, then you're going to have to edit the .tld for <input> to include your custom tag. It may be easier to make a new tag and resources just to avoid having to combine your code with the Java and .tld of the <input>.
Also, check out BeanUtils as suggested by Tim Holloway.