如何通过param过滤实时数据库对象？

Question

    DatabaseReference database = FirebaseDatabase.getInstance().getReference();
    DatabaseReference ref = database.child("words");

    Query word = ref.orderByChild("lang1").equalTo("home");
    word.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for(DataSnapshot singleSnapshot : dataSnapshot.getChildren()){
                Word w = singleSnapshot.getValue(Word.class);
                Log.i(String.valueOf(R.string.app_name), new Gson().toJson(w));
            }
        }
        @Override
        public void onCancelled(DatabaseError databaseError) {
            //Log.e(TAG, "onCancelled", databaseError.toException());
        }
    });

你能告诉我我做错了什么吗？在这里，我试图得到一些＆＃34; Words＆＃34;来自DB＆amp;将Json发送到控制台...

UPD：导入的JSON文件

{
    "words" : {
        "1" : {
            "id" : 1,
            "lang1" : "s1",
            "lang2" : "d1",
            "type" : "a"
        } , 
        "2" : {
            "id" : 2,
            "lang1" : "s2",
            "lang2" : "d2",
            "type" : "a"
        } // ...
    }
}