I was asked by the company I work to create a web user interface for a fleet managment system they have developed.

This system is written in java so I thought that the library I should compatible with java or language neutral. Additionally it should be free/open source, as well as full-featured 

After a small search I found the following libraries:

1)
<http://dhtmlx.com/index.shtml>

2) <https://vaadin.com/home>

Currently I face the following critical question: should I rely on a server side library for the creation of the User Interface or should I prefer a client side one ?

What is more are there any other important web user interface libraries that I should be aware of ?

Since I do not have any experience in the topic, every advice will be very useful : )