I am trying to validate that a username is unique on a registration form and would like to verify the uniqueness of the username right after the client types it as opposed to performing this server side after the form has been submitted.
Should I collect a resultSet from the database, store it in an array and then pass this along to the jsp page in the form of a bean (I am using a model 2 design so the user passes through a servlet before arriving at the jsp page)? What if the array is very large? How do I bring this data into javascript?
Alternatively, is there a way to do the query using ajax and javascript all on the client side? Maybe its possible to somehow run the query in the background?
I am really just looking for some direction because I am clueless as to what to even begin researching something like this. Is this even a smart move, performance wise?
I’d use “AJAX” for this.
Here’s one approach: set up a blur() handler on the username text field of your form. When the blur() method is invoked, you post the username to the backend code; it verifies it and returns some appropriate response. You then parse the response and change the CSS class on the username text field (e.g., turning it red) — or do whatever else visually you want to do to indicate “username in use.”
Either way, you’ve got to get the username from the client to the server for verification; you wouldn’t want any mechanism which allowed the client to directly use the DB (think security/exploits/etc).
If you’re not already familiar, check out jQuery (http://jquery.com/) to make your client-side life much easier.