We have good support for JSON in java http://blog.locut.us/main/2009/10/14/which-is-the-best-java-json-library.html but what about BSON.
What library do you know that provides BSON support for java? It should obviously be efficient in runtime.
Answer
You can use the MongoDB driver for Java to store a BSON object, then convert that to a String which you can then wrap with JSONObject.
For example, here's how I'll create a regular document:
BasicDBObject obj = new BasicDBObject();
obj.put("name", "Matt");
obj.put("date", new Date());
Then, to get a String representation of the object, simply call:
String bsonString = obj.toString();
Wrap it with a JSONObject and get the date attribute, which should return it in a BSON-compliant format.
JSONObject newObject = new JSONObject(bsonString);
System.out.println(newObject.get("date"));
The resulting output is something like:
{"$date":"2012-08-10T05:22:53.872Z"}