title: SpringMVC Ajax validation
body: <p>I have a Spring Mvc 3 form that POST to a controller, in the controller i make calls to execute DML statements. I also have a separate validation class that implements Validator and is called in my Controller. I do both simple and complex validation in there like check if user name exist and return an error message if it exist. </p>
  
  <p>I would like to use ajax to validate only the user name field when i tab out of the field on the view, but i would like to make a call to the already implemented validation i have and only validate the username field. </p>
  
  <p>How can i achieve this, will i need to make a call in Ajax to the Controller class and have a separate @RequestMapping to handle this only? Can i have an example om how this should be implemented. </p>