Custom validation on Spring security

gistfile1.txt

/* the filter */

public class MyAuthenticationProcessingFilter extends AbstractAuthenticationProcessingFilter {

	@Autowired
	private transient Validator validator;

	protected MyAuthenticationProcessingFilter(String defaultFilterProcessesUrl) {
		super(defaultFilterProcessesUrl);
	}

	@Override
	public Authentication attemptAuthentication(HttpServletRequest request, HttpServletResponse response) throws AuthenticationException, IOException, ServletException {
		
		LoginForm loginForm = new LoginForm();
		loginForm.setUsername(request.getParameter("username"));
		loginForm.setPassword(request.getParameter("password"));

        Errors errors = new BeanPropertyBindingResult(loginForm, "login");
        
        if(!this.isValid(validator, errors, loginForm)) {
        	throw new AuthenticationRequiredFieldsException("validation failed",errors);
        }

        MyAuthentication myAuthentication = new MyAuthentication(loginForm.getUsername(), loginForm.getPassword());
		Authentication authResult = this.getAuthenticationManager().authenticate(myAuthentication);

		return authResult;
	}
	
	public class AuthenticationRequiredFieldsException extends AuthenticationException {

		private static final long serialVersionUID = -3613393016881542212L;
		private Errors errors;

		public AuthenticationRequiredFieldsException(String msg, Throwable error) {
			super(msg, error);
		}

		public AuthenticationRequiredFieldsException(String msg) {
			super(msg);
		}
		
		public AuthenticationRequiredFieldsException(String msg, Errors errors) {
			super(msg);
			this.errors = errors;
		}

		public Errors getErrors() {
			return errors;
		}
	}
	
	public class LoginForm {
		
		@NotEmpty
		@Length(min=5,max=30)
		private String username;
		@NotEmpty
		@Length(min=5,max=60)
		private String password;
		
		public String getUsername() {
			return username;
		}
		public void setUsername(String username) {
			this.username = username;
		}
		public String getPassword() {
			return password;
		}
		public void setPassword(String password) {
			this.password = password;
		}
	}
}

/** then using on the jsp that prints the login form:

<form:form commandName="login">
	<form:errors path="*" cssClass="error"></form:errors>
</form:form>

*/