Java 5 command initializer

Does anyone know of something that initializes a command object from request where there are arbitrary number of nested and/or indexed elements?
Something you could put in Object formBackingObject(HttpServletRequest request) that would instantiate nested classses and add indexed elements as necessary? With java 5 you can specify type of collections, so if all command classes were concrete classes rather than interfaces, should be possible. I could write one, but wondered if there was already something like this.

For example:

class article
article.title
article.author
article.links

class author
author.name

class link
link.text
link.url
link.newWindow

request params:

title=foo
author.name=Harold

links[0].text=abcd
links[0].url=http://abcd.com
links[0].newWindow=whatever

links[1].text=abcd
links[1].url=http://abcd.com
links[1].newWindow=whatever