مشكلة في جلب بيانات من firebase في اندرويد

احاول جلب بيانات من الـfirebase لكن يظهر لدي الخطأ التالي:

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.luvtas.campingau, PID: 11763
    com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.luvtas.campingau.Model.CamperSiteModel
        at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertBean(CustomClassMapper.java:436)
        at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.deserializeToClass(CustomClassMapper.java:232)
        at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertToCustomClass(CustomClassMapper.java:80)
        at com.google.firebase.database.DataSnapshot.getValue(DataSnapshot.java:203)
        at com.luvtas.campingau.Fragment.ExploreFragment$3.onDataChange(ExploreFragment.java:128)
        at com.google.firebase.database.core.ValueEventRegistration.fireEvent(ValueEventRegistration.java:75)
        at com.google.firebase.database.core.view.DataEvent.fire(DataEvent.java:63)
        at com.google.firebase.database.core.view.EventRaiser$1.run(EventRaiser.java:55)
        at android.os.Handler.handleCallback(Handler.java:790)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

هذا هو الكود:

private RecyclerView recyclerView;
    private CamperSiteAdapter camperSiteAdapter;
    private List<CamperSiteModel> camperSiteModel;
    EditText seatch_bar;
private void readCampSite(){
        DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Cte");
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                if(seatch_bar.getText().toString().equals("")){
                    camperSiteModel.clear();
                    for(DataSnapshot snapshot : dataSnapshot.getChildren()){
                        CamperSiteModel camperSiteModel1 = snapshot.getValue(CamperSiteModel.class);
                        camperSiteModel.add(camperSiteModel1);
                    }
                    camperSiteAdapter.notifyDataSetChanged();
                }
            }
            @Override
            public void onCancelled(@NonNull DatabaseError error) {
            }
        });
    }

كود الـmodel:

 public CamperSiteModel() {
    }
    public CamperSiteModel(String camperSiteID, String camperSiteName, String camperSiteImage, String camperSiteType, String camperSiteDistance, String camperSiteInfo, String camperSiteSummary, String camperSiteAddress, String camperSiteLatitude, String camperSiteLongitude, String camperSitePrice1, String camperSitePrice2, String camperSiteEmail, String camperSiteSub) {
        CamperSiteID = camperSiteID;
        CamperSiteName = camperSiteName;
        CamperSiteImage = camperSiteImage;
        CamperSiteType = camperSiteType;
        CamperSiteDistance = camperSiteDistance;
        CamperSiteInfo = camperSiteInfo;
        CamperSiteSummary = camperSiteSummary;
        CamperSiteAddress = camperSiteAddress;
        CamperSiteLatitude = camperSiteLatitude;
        CamperSiteLongitude = camperSiteLongitude;
        CamperSitePrice1 = camperSitePrice1;
        CamperSitePrice2 = camperSitePrice2;
        CamperSiteEmail = camperSiteEmail;
        CamperSiteSub = camperSiteSub;
    }

فما هي المشكلة ؟