title: Firebase No properties to serialize found on class
body: <p>I'm bloqued creating a Firebase Database. </p>
  
  <p>I'm trying to model a class. A very simple class:</p>
  
  <pre><code>package com.glups.model;
  
  import com.google.firebase.database.IgnoreExtraProperties;
  
  @IgnoreExtraProperties
  public class AlumnoFB {
  
      private String nombre;
      private String apellidos;
      private String telefono;
      private String email;
      private Boolean tieneWhatsapp;
      private Boolean tieneTelegram;
      private Boolean tieneHangouts;
      private Long formaPago;
      private Double ratioHora;
      private Double precioHora;
      private Double horasCompensadas;
  
      public AlumnoFB() {
          // Default constructor required for calls to DataSnapshot.getValue(User.class)
      }
  
      public AlumnoFB(String nombre,
                      String apellidos,
                      String telefono,
                      String email,
                      Boolean tieneWhatsapp,
                      Boolean tieneTelegram,
                      Boolean tieneHangouts,
                      Long formaPago,
                      Double ratioHora,
                      Double precioHora,
                      Double horasCompensadas) {
          this.nombre = nombre;
          this.apellidos = apellidos;
          this.telefono = telefono;
          this.email = email;
          this.tieneWhatsapp = tieneWhatsapp;
          this.tieneTelegram = tieneTelegram;
          this.tieneHangouts = tieneHangouts;
          this.formaPago = formaPago;
          this.ratioHora = ratioHora;
          this.precioHora = precioHora;
          this.horasCompensadas = horasCompensadas;
      }
  }
  </code></pre>
  
  <p>that is almost like a sample class from Firebase.</p>
  
  <p>Application user obtained from getUser() has been logged on Firebase.</p>
  
  <p>When I call SetValue:</p>
  
  <pre><code>AlumnoFB alumno = new AlumnoFB("", "", "", "", false, false, false, ((Integer)FormaPago.INT_NO_PAGADO).longValue(), 0.0, 0.0, 0.0);
      mDatabase.child("AlumnoFB").child(ControlClasesFirebase.getUser().getUid()).setValue(alumno) ;
  </code></pre>
  
  <p>A fatal exception raises.</p>
  
  <pre><code>06-10 10:17:37.179 13841-13841/com.glups.controlclases E/AndroidRuntime: FATAL EXCEPTION: main
  Process: com.glups.controlclases, PID: 13841 com.google.firebase.database.DatabaseException: No properties to serialize found on class com.glups.model.AlumnoFB
  at com.google.android.gms.internal.zzaix$zza.&lt;init&gt;(Unknown Source)
  at com.google.android.gms.internal.zzaix.zzj(Unknown Source)
  at com.google.android.gms.internal.zzaix.zzaw(Unknown Source)
  at com.google.android.gms.internal.zzaix.zzav(Unknown Source)
  at com.google.firebase.database.DatabaseReference.zza(Unknown Source)
  at com.google.firebase.database.DatabaseReference.setValue(Unknown Source)
  at com.glups.controlclases.MainActivity$4.onClick(MainActivity.java:305)
  at android.view.View.performClick(View.java:4780)
  at android.view.View$PerformClick.run(View.java:19866)
  at android.os.Handler.handleCallback(Handler.java:739)
  at android.os.Handler.dispatchMessage(Handler.java:95)
  at android.os.Looper.loop(Looper.java:135)
  at android.app.ActivityThread.main(ActivityThread.java:5258)
  at java.lang.reflect.Method.invoke(Native Method)
  at java.lang.reflect.Method.invoke(Method.java:372)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
  </code></pre>
  
  <p>I've checked types, and all are accepted. What's wrong?</p>