@Override
	public DBObject convert(Tuple source) {
		DBObject dbo = new BasicDBObject();
		for (int i = 0; i < source.getFieldCount(); i++) {
			String name = source.getFieldNames().get(i);
			if (name.equals(idField)) {
				dbo.put("_id", source.getValue(i));
			}
			else {
				dbo.put(name, source.getValue(i));
			}
		}
		return dbo;
	}
Set the tuple field name which will be used as the Mongo _id. If not set, the MongoDriver will
will assign a ObjectId with a generated value.

@param idField the name of the field to use as the identity in MongoDB.
extensions/spring-xd-extension-mongodb/src/main/java/org/springframework/xd/mongodb/TupleWriteConverter.java