title: cakephp : validating a login Form using $validate array
body: <p>Can Any One help me to Validate a login Form in cakePHP?<br>
  I need to validate the login form just like how we validate a registration form using <code>$validate</code> array in Model.</p>
  
  <p><strong>EDIT :</strong> Since I am using Auth Component for Authentication. It directly goes to login action in Auth Component with out validating from the user model.So it will only show the error message as "invalid username/password" even though i simply press the login button without giving any username or password.I need to show invalid username by the side of the username text box if the username left blank</p>
  
  <p>Any help will be appreciated.</p>