Map to ContentValues (Abusing Parcelable)

This post is about removing some of the pain from inserting JSON into SQLite (or any Map thing to any ContentValues-based system) and vice-versa.

ContentValues is the proper way to give SQLite data to insert. However, the methods for putting stuff in it are typed. It has to be an int, a String… and you have to know the type of Object you are inserting.

That’s good, because you are not supposed to put anything else in a ContentValues.

That’s no so good, because in the end, it is simply a Map that holds the data no matter what you give it. It add complexity with little gain.

It can happen that you have data you want to insert, you know you only have valid data types, but you don’t know which is which.

For example, you receive a JSONObject from a webservice that you need to insert or update.

Parcelable comes to the rescue.

Parceling a ContentValues only parcels the underlying HashMap, and unparceling then calls the private constructor ContentValues(Map). The trick is to parcel a HashMap, and then unparcel it as a ContentValues. Voilà.

Map to ContentValues

Parcel parcel = obtain();
parcel.writeMap(map);
parcel.setDataPosition(0);
ContentValues values = ContentValues.CREATOR.createFromParcel(parcel);

For example, your map could come from a JSONObject:

JSONObject to Map

Map<String, Object> map = new HashMap<String, Object>();
for (String key : jObj.keys()) {
    map.put(key, jObj.get(key);
}

map can then be inserted in database (provided you are sure of your data structure).

Note regarding unsupported types

ContentValues can be used in different use cases, but in the case of SQLite, SQLiteConnection.bindArguments tends to indicate that default behavior with unknown Object types is to toString them.

Please note that the reverse operation works as well, meaning it is quite easy to put a ContentValues into a JSONObject (or any other formatting that takes a Map as input)

It is also possible to use reflection to access the Map field from the ContentValue and get/set it. However, I find reflection is cumbersome in Java (although probably more efficient in this case).