Added a property is_body_json

The above property returns True if the request body contains valid json, if the body doesn't contains valid json then it returns false. This can be used in the situations when we want to validate the json of body.

flask/wrappers.py

@@ -121,7 +121,20 @@ class Request(RequestBase):
         if mt.startswith('application/') and mt.endswith('+json'):
             return True
         return False
+    
+    @property
+    def is_body_json(self):
+        """
+            Validates wether the body consists valid json or not.
+        """
+        request_charset = self.mimetype_params.get('charset')
+        try:
+            json.loads(request_charset)
+        except ValueError, e:
+            return False
+        return True    
 
+    
     def get_json(self, force=False, silent=False, cache=True):
         """Parses the incoming JSON request data and returns it.  By default
         this function will return ``None`` if the mimetype is not