Added json serialisation support

- Added to_json and from_json to Document (MongoEngine/mongoengine#1)
- Added to_json and from_json to QuerySet (MongoEngine/mongoengine#131)

mongoengine/base/document.py

@@ -2,6 +2,7 @@ import operator
 from functools import partial
 
 import pymongo
+from bson import json_util
 from bson.dbref import DBRef
 
 from mongoengine import signals
@@ -253,6 +254,15 @@ class BaseDocument(object):
         if errors:
             raise ValidationError('ValidationError', errors=errors)
 
+    def to_json(self):
+        """Converts a document to JSON"""
+        return json_util.dumps(self.to_mongo())
+
+    @classmethod
+    def from_json(cls, json_data):
+        """Converts json data to an unsaved document instance"""
+        return cls._from_son(json_util.loads(json_data))
+
     def __expand_dynamic_values(self, name, value):
         """expand any dynamic values to their correct types / values"""
         if not isinstance(value, (dict, list, tuple)):