title: Play Framework Error on BindRequest
body: <p>I'm getting the following error on Play 2.1.3:
  [RuntimeException: Cannot instantiate class controllers.Application$User. It must have a default constructor]</p>
  
  <p>Here's my Application.java file...I can't tell what I'm doing wrong! This occurs when I make a POST request to /login.</p>
  
  <pre><code>package controllers;
  
  import play.mvc.*;
  import play.data.*;
  import views.html.*;
  
  public class Application extends Controller {
  
      private static boolean loggedin = false;
      private static User currentUser;
      private static Form&lt;User&gt; LoginForm = Form.form(User.class);
  
      public static Result index() {
  
          String message, title;
  
          if(!loggedin)
          {
              title = "Login";
              message = "Please log in.";
          }
          else
          {
              title = "Welcome";
              message = "You are logged in!";
          }
          return ok(index.render(title, message, loggedin));
      }
  
      public static Result login() {
  
          currentUser = LoginForm.bindFromRequest().get();
  
          if(currentUser.getUsername().equals("test") &amp;&amp; currentUser.getPassword().equals("password")) {
              loggedin = true;
              return redirect(routes.Application.index());
          }
          else {
              String title = "Login";
              String message = "An error occurred. Please try logging in again.";
              return ok(index.render(title, message, loggedin));
          }
      }
  
      static class User {
          private String username;
          private String password;
  
          public User() {
              this.username = "";
              this.password = "";
          }
  
          public String getUsername() {
              return this.username;
          }
          public String getPassword() {
              return this.password;
          }
      }
  
  }
  </code></pre>