Using JSON with MongoDB?

问题:

My application uses JSON objects a lot (org.json.JSONArray and friends). What's the most efficient way to store these into Mongo DBObjects so they can be queried? BasicDBObject can't serialize a JSONArray--there seems to be no interoperability between these two hierarchies at all.

回答1:

com.mongodb.util.JSON has a method to parse a JSON string into DBObject. The default JSONCallback will return a BasicDBObject or BasicDBList according to input string.

Object jsonObj = ...; //any of your org.json objects
Object o = com.mongodb.util.JSON.parse(jsonObj.toString());
DBObject dbObj = (DBObject) o;

回答2:

OK it seems there is no interoperability, so I rolled my own. Busywork to get around the type system:

public class Util {
    public static DBObject encode(JSONArray a) {
        BasicDBList result = new BasicDBList();
        try {
            for (int i = 0; i < a.length(); ++i) {
                Object o = a.get(i);
                if (o instanceof JSONObject) {
                    result.add(encode((JSONObject)o));
                } else if (o instanceof JSONArray) {
                    result.add(encode((JSONArray)o));
                } else {
                    result.add(o);
                }
            }
            return result;
        } catch (JSONException je) {
            return null;
        }
    }

    public static DBObject encode(JSONObject o) {
        BasicDBObject result = new BasicDBObject();
        try {
            Iterator i = o.keys();
            while (i.hasNext()) {
                String k = (String)i.next();
                Object v = o.get(k);
                if (v instanceof JSONArray) {
                    result.put(k, encode((JSONArray)v));
                } else if (v instanceof JSONObject) {
                    result.put(k, encode((JSONObject)v));
                } else {
                    result.put(k, v);
                }
            }
            return result;
        } catch (JSONException je) {
            return null;
        }
    }
}

回答3:

i don't know about java mongo driver, but in c# mongo driver has BsonSerializer class. You can use it like following code:

var q = BsonSerializer.Deserialize<MyDocument>("{ jsonValueName:jsonValue }"); 

plz check mongo-java-driver, i thank it should contain the same facilities

also look at bson4jackson

回答4:

This works, and throws the question as to why the Mongo folks decided to have an Object return type instead of a DBObject: does anyone know?

A good alternative, if you have a lot of JSON in your app, would be to use Jackson for the (de)serialization.