Playframework: [RuntimeException: java.lang.reflec

I'm trying to create a simple login based on the Zentask sample --zentask - playframework, however when I click the login button which calls the Application.authenticate actions, it gives runtime exception. I have marked the line with -- error

[RuntimeException: java.lang.reflect.InvocationTargetException]

Application.java

public class Application extends Controller {

.........

public static class Login 
{
    public String email;
    public String password;

    public String validate() 
    {
        if (User.authenticate(email, password) == null) {
          return "Invalid user or password";
        }
        return null;
    }
}

   public static Result authenticate() 
    {
        Form<Login> loginForm = form(Login.class).bindFromRequest();  //--- error
        if(loginForm.hasErrors()) {
            return badRequest(login.render(loginForm));
        } else {
            session("email", loginForm.get().email);
            return redirect(
                routes.Application.index()
            );
        }
    }
}

I understand it has something to do with the validate function in Login Class, because when I remove the call to User.authenticate in the validate function it works without error. But I am unable to figure it out.

The user class is as -

@Entity
public class User extends Model
{
    @Id
    @Constraints.Required
    @Formats.NonEmpty
    public String userId;

    @OneToOne(cascade=CascadeType.PERSIST)
    AccountDetails accDetails;


    public static Model.Finder<String,User> find = new Model.Finder<String,User>(String.class, User.class);



    // Authenticate the user details
    public static User authenticate(String email, String password) 
    {
        String tempId = AccountDetails.authenticate(email, password).userId;

        return find.ref(tempId);
    }

    .. . . . . . .

}

and the AccountDetails Class -

@Entity
public class AccountDetails extends Model
{
    @Id
    String userId;

    @Constraints.Required
    String emailId;

    @Constraints.Required
    String password;

    public static Model.Finder<String,AccountDetails> find = 
            new Model.Finder<String,AccountDetails>(String.class, AccountDetails.class);


    public static AccountDetails authenticate(String email, String password) 
    {       
        return find.where()
            .eq("email", email)
            .eq("password", password)
            .findUnique();
    }

}

I have to assume a lot but if this is what your stacktrace looked like:

play.api.Application$$anon$1: Execution exception[[RuntimeException: java.lang.reflect.InvocationTargetException]]
                at play.api.Application$class.handleError(Application.scala:293) ~[play_2.10.jar:2.2.3]
                at play.api.DefaultApplication.handleError(Application.scala:399) [play_2.10.jar:2.2.3]
                at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$3$$anonfun$applyOrElse$3.apply(PlayDefaultUpstreamHandler.scala:264) [play_2.10.jar:2.2.3]
                at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$3$$anonfun$applyOrElse$3.apply(PlayDefaultUpstreamHandler.scala:264) [play_2.10.jar:2.2.3]
                at scala.Option.map(Option.scala:145) [scala-library.jar:na]
                at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$3.applyOrElse(PlayDefaultUpstreamHandler.scala:264) [play_2.10.jar:2.2.3]
        ...
        Caused by: java.lang.NullPointerException: null
                at models.User.authenticate(User.java:26) ~[na:na]
                at controllers.Application$Login.validate(Application.java:50) ~[na:na]
                at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_05]
                at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_05]
                at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_05]
                at java.lang.reflect.Method.invoke(Method.java:483) ~[na:1.8.0_05]

then the cause of the problem is actually hinted at by the NPE in your User class. If you enter bogus credentials, your finder will not find anything and return null in AccountDetails.authenticate().

So in the method below you do not check for null and try and get the userId, which causes the NPE:

public static User authenticate(String email, String password) {
  String tempId = AccountDetails.authenticate(email, password).userId;

  return find.ref(tempId);
}

If you just check for null properly you will get the desired functionality:

public static User authenticate(String email, String password) {
    User user = null;

    AccountDetails accountDetails = AccountDetails.authenticate(email, password);
    if (accountDetails != null) {
        user = find.ref(accountDetails.userId);
    }

    return user;
}