Added generic JsonResponse class

Based on http://djangosnippets.org/snippets/154/

cms/djangoapps/contentstore/views/course.py

@@ -7,8 +7,9 @@ from django.contrib.auth.decorators import login_required
 from django_future.csrf import ensure_csrf_cookie
 from django.conf import settings
 from django.core.exceptions import PermissionDenied
-from django.http import HttpResponse, HttpResponseBadRequest
 from django.core.urlresolvers import reverse
+from django.http import HttpResponse, HttpResponseBadRequest
+from util.json_request import JsonResponse
 from mitxmako.shortcuts import render_to_response
 
 from xmodule.modulestore.django import modulestore
@@ -447,18 +448,16 @@ def textbook_index(request, org, course, name):
 
     if request.is_ajax():
         if request.method == 'GET':
-            return HttpResponse(json.dumps(course_module.pdf_textbooks), content_type="application/json")
+            return JsonResponse(course_module.pdf_textbooks)
         elif request.method == 'POST':
             try:
                 course_module.pdf_textbooks = validate_textbook_json(request.body)
             except TextbookValidationError as e:
-                msg = {"error": e.message}
-                return HttpResponseBadRequest(json.dumps(msg), content_type="application/json")
+                return JsonResponse({"error": e.message}, status=400)
             if not any(tab['type'] == 'pdf_textbooks' for tab in course_module.tabs):
                 course_module.tabs.append({"type": "pdf_textbooks"})
             store.update_metadata(course_module.location, own_metadata(course_module))
-
-            return HttpResponse('', content_type="application/json", status=204)
+            return JsonResponse('', status=204)
     else:
         upload_asset_url = reverse('upload_asset', kwargs={
             'org': org,

common/djangoapps/util/json_request.py

 from functools import wraps
 import copy
 import json
+from django.core.serializers import serialize
+from django.core.serializers.json import DjangoJSONEncoder
+from django.db.models.query import QuerySet
+from django.http import HttpResponse
 
 
 def expect_json(view_function):
@@ -21,3 +25,20 @@ def expect_json(view_function):
             return view_function(request, *args, **kwargs)
 
     return expect_json_with_cloned_request
+
+
+class JsonResponse(HttpResponse):
+    """
+    Django HttpResponse subclass that has sensible defaults for outputting JSON.
+    """
+    def __init__(self, object=None, *args, **kwargs):
+        if object in (None, ""):
+            content = ""
+            kwargs.setdefault("status", 204)
+        elif isinstance(object, QuerySet):
+            content = serialize('json', object)
+        else:
+            content = json.dumps(object, indent=2, cls=DjangoJSONEncoder,
+                                 ensure_ascii=False)
+        kwargs.setdefault("content_type", "application/json")
+        super(JsonResponse, self).__init__(content, *args, **kwargs)