Welcome to the JavaRanch, Buddhika!
Wow. MDI kind of went out of style a long time ago. I did some Googling, and didn't turn up much.
For basic resizable multi-pane windows, the CSS DIV in conjunction with Facelets suffices.
However, full MDI, with a free-form workspace would require a lot of work, and since, like I said, MDI isn't really all that popular anymore, you'd probably have to do most of the work itself.
About the closest thing to an MDI look-and-feel in
J2Ee you'd get without significant work would be to set up a portal where the various panes would be backed by J2EE portlets. LifeRay is a popular portal server, and we have a forum for portals here on the Ranch. You can write portlets using a number of different frameworks, including JSF.