diff --git a/nailgun/nailgun/api/v1/handlers/assignment.py b/nailgun/nailgun/api/v1/handlers/assignment.py
index cc36780c76..eb80b5b88a 100644
--- a/nailgun/nailgun/api/v1/handlers/assignment.py
+++ b/nailgun/nailgun/api/v1/handlers/assignment.py
@@ -19,7 +19,8 @@ Handlers dealing with nodes assignment
 """
 
 from nailgun.api.v1.handlers.base import BaseHandler
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.validators.assignment import NodeAssignmentValidator
 from nailgun.api.v1.validators.assignment import NodeUnassignmentValidator
 
@@ -31,7 +32,8 @@ class NodeAssignmentHandler(BaseHandler):
     """Node assignment handler"""
     validator = NodeAssignmentValidator
 
-    @content
+    @handle_errors
+    @validate
     def POST(self, cluster_id):
         """:returns: Empty string
 
@@ -62,7 +64,8 @@ class NodeUnassignmentHandler(BaseHandler):
     """Node assignment handler"""
     validator = NodeUnassignmentValidator
 
-    @content
+    @handle_errors
+    @validate
     def POST(self, cluster_id):
         """:returns: Empty string
 
diff --git a/nailgun/nailgun/api/v1/handlers/base.py b/nailgun/nailgun/api/v1/handlers/base.py
index ca231c4f5b..1a94997eae 100644
--- a/nailgun/nailgun/api/v1/handlers/base.py
+++ b/nailgun/nailgun/api/v1/handlers/base.py
@@ -15,12 +15,13 @@
 #    under the License.
 
 from datetime import datetime
+from decorator import decorator
+from oslo_serialization import jsonutils
 import six
 import traceback
+import yaml
 
-from decorator import decorator
 from distutils.version import StrictVersion
-from oslo_serialization import jsonutils
 from sqlalchemy import exc as sa_exc
 import web
 
@@ -31,7 +32,6 @@ from nailgun.api.v1.validators.orchestrator_graph import \
 from nailgun import consts
 from nailgun.db import db
 from nailgun import errors
-from nailgun.errors.base import NailgunException
 from nailgun.logger import logger
 from nailgun import objects
 from nailgun.objects.serializers.base import BasicSerializer
@@ -271,40 +271,25 @@ class BaseHandler(object):
         else:
             return default
 
+    @staticmethod
+    def get_requested_mime():
+        accept = web.ctx.env.get("HTTP_ACCEPT", "application/json")
+        accept = accept.strip().split(',')[0]
+        accept = accept.split(';')[0]
+        return accept
 
-def content_json(func, cls, *args, **kwargs):
-    json_resp = lambda data: (
-        jsonutils.dumps(data)
-        if isinstance(data, (dict, list)) or data is None else data
-    )
 
-    request_validate_needed = True
+def json_resp(data):
+    if isinstance(data, (dict, list)) or data is None:
+        return jsonutils.dumps(data)
+    else:
+        return data
 
-    resource_type = "single"
-    if issubclass(
-        cls.__class__,
-        CollectionHandler
-    ) and not func.func_name == "POST":
-        resource_type = "collection"
-
-    if (
-        func.func_name in ("GET", "DELETE") or
-        getattr(cls.__class__, 'validator', None) is None or
-        resource_type == "single" and not cls.validator.single_schema or
-        resource_type == "collection" and not cls.validator.collection_schema
-    ):
-        request_validate_needed = False
 
+@decorator
+def handle_errors(func, cls, *args, **kwargs):
     try:
-        if request_validate_needed:
-            BaseHandler.checked_data(
-                cls.validator.validate_request,
-                resource_type=resource_type
-            )
-
-        resp = func(cls, *args, **kwargs)
-    except web.notmodified:
-        raise
+        return func(cls, *args, **kwargs)
     except web.HTTPError as http_error:
         if http_error.status_code != 204:
             web.header('Content-Type', 'application/json', unique=True)
@@ -316,7 +301,7 @@ def content_json(func, cls, *args, **kwargs):
         else:
             http_error.data = json_resp(http_error.data)
         raise
-    except NailgunException as exc:
+    except errors.NailgunException as exc:
         logger.exception('NailgunException occured')
         http_error = BaseHandler.http(400, exc.message)
         web.header('Content-Type', 'text/plain')
@@ -336,62 +321,66 @@ def content_json(func, cls, *args, **kwargs):
         web.header('Content-Type', 'text/plain')
         raise http_error
 
-    web.header('Content-Type', 'application/json', unique=True)
-    return json_resp(resp)
+
+@decorator
+def validate(func, cls, *args, **kwargs):
+    request_validation_needed = True
+
+    resource_type = "single"
+    if issubclass(
+        cls.__class__,
+        CollectionHandler
+    ) and not func.func_name == "POST":
+        resource_type = "collection"
+
+    if (
+        func.func_name in ("GET", "DELETE") or
+        getattr(cls.__class__, 'validator', None) is None or
+        (resource_type == "single" and not cls.validator.single_schema) or
+        (resource_type == "collection" and not cls.validator.collection_schema)
+    ):
+        request_validation_needed = False
+
+    if request_validation_needed:
+        BaseHandler.checked_data(
+            cls.validator.validate_request,
+            resource_type=resource_type
+        )
+
+    return func(cls, *args, **kwargs)
 
 
-def content(*args, **kwargs):
-    """Set context-type of response based on Accept header
+@decorator
+def serialize(func, cls, *args, **kwargs):
+    """Set context-type of response based on Accept header.
 
     This decorator checks Accept header received from client
     and returns corresponding wrapper (only JSON is currently
     supported). It can be used as is:
 
-    @content
-    def GET(self):
-        ...
-
-    Default behavior may be overriden by passing list of
-    exact mimetypes to decorator:
-
-    @content(["text/plain"])
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         ...
     """
-    # TODO(ikutukov): this decorator is not coherent and doing more
-    # than just a response mimetype setting via type-specific content_json
-    # method that perform validation.
-    # Before you start to implement handler business logic ensure that
-    # @content decorator not already doing what you are planning to write.
-    # I think that validation routine and common http headers formation not
-    # depending on each other and should be decoupled. At least they should
-    # not be under one decorator with abstract name.
+    accepted_types = (
+        "application/json",
+        "application/x-yaml",
+        "*/*"
+    )
+    accept = cls.get_requested_mime()
+    if accept not in accepted_types:
+        raise BaseHandler.http(415)
 
-    exact_mimetypes = None
-    if len(args) >= 1 and isinstance(args[0], list):
-        exact_mimetypes = args[0]
-
-    @decorator
-    def wrapper(func, *args, **kwargs):
-        accept = web.ctx.env.get("HTTP_ACCEPT", "application/json")
-        accepted_types = [
-            "application/json",
-            "*/*"
-        ]
-        if exact_mimetypes and isinstance(exact_mimetypes, list):
-            accepted_types = exact_mimetypes
-        if any(map(lambda m: m in accept, accepted_types)):
-            return content_json(func, *args, **kwargs)
-        else:
-            raise BaseHandler.http(415)
-
-    # case of @content without arguments, meaning arg[0] to be callable
-    # handler
-    if len(args) >= 1 and callable(args[0]):
-        return wrapper(args[0], *args[1:], **kwargs)
-
-    # case of @content(["mimetype"]) with explicit arguments
-    return wrapper
+    resp = func(cls, *args, **kwargs)
+    if accept == 'application/x-yaml':
+        web.header('Content-Type', 'application/x-yaml', unique=True)
+        return yaml.dump(resp, default_flow_style=False)
+    else:
+        # default is json
+        web.header('Content-Type', 'application/json', unique=True)
+        return jsonutils.dumps(resp)
 
 
 class SingleHandler(BaseHandler):
@@ -399,7 +388,9 @@ class SingleHandler(BaseHandler):
     single = None
     validator = BasicValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, obj_id):
         """:returns: JSONized REST object.
 
@@ -407,9 +398,11 @@ class SingleHandler(BaseHandler):
                * 404 (object not found in db)
         """
         obj = self.get_object_or_404(self.single, obj_id)
-        return self.single.to_json(obj)
+        return self.single.to_dict(obj)
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, obj_id):
         """:returns: JSONized REST object.
 
@@ -423,9 +416,10 @@ class SingleHandler(BaseHandler):
             instance=obj
         )
         self.single.update(obj, data)
-        return self.single.to_json(obj)
+        return self.single.to_dict(obj)
 
-    @content
+    @handle_errors
+    @validate
     def DELETE(self, obj_id):
         """:returns: Empty string
 
@@ -452,16 +446,19 @@ class CollectionHandler(BaseHandler):
     validator = BasicValidator
     eager = ()
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         """:returns: Collection of JSONized REST objects.
 
         :http: * 200 (OK)
         """
         q = self.collection.eager(None, self.eager)
-        return self.collection.to_json(q)
+        return self.collection.to_list(q)
 
-    @content
+    @handle_errors
+    @validate
     def POST(self):
         """:returns: JSONized REST object.
 
@@ -495,7 +492,9 @@ class DBSingletonHandler(BaseHandler):
 
         return instance
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         """Get singleton object from DB
 
@@ -504,9 +503,11 @@ class DBSingletonHandler(BaseHandler):
         """
         instance = self.get_one_or_404()
 
-        return self.single.to_json(instance)
+        return self.single.to_dict(instance)
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self):
         """Change object in DB
 
@@ -520,9 +521,11 @@ class DBSingletonHandler(BaseHandler):
 
         self.single.update(instance, data)
 
-        return self.single.to_json(instance)
+        return self.single.to_dict(instance)
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PATCH(self):
         """Update object
 
@@ -538,7 +541,7 @@ class DBSingletonHandler(BaseHandler):
             self.single.serializer.serialize(instance), data
         ))
 
-        return self.single.to_json(instance)
+        return self.single.to_dict(instance)
 
 
 # TODO(enchantner): rewrite more handlers to inherit from this
@@ -557,7 +560,8 @@ class DeferredTaskHandler(BaseHandler):
     def get_options(cls):
         return {}
 
-    @content
+    @handle_errors
+    @validate
     def PUT(self, cluster_id):
         """:returns: JSONized Task object.
 
@@ -618,7 +622,9 @@ class OrchestratorDeploymentTasksHandler(SingleHandler):
 
     validator = GraphSolverTasksValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, obj_id):
         """:returns: Deployment tasks
 
@@ -654,7 +660,9 @@ class OrchestratorDeploymentTasksHandler(SingleHandler):
                                      'name.'.format(e.task_name))
         return tasks
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, obj_id):
         """:returns:  Deployment tasks
 
diff --git a/nailgun/nailgun/api/v1/handlers/capacity.py b/nailgun/nailgun/api/v1/handlers/capacity.py
index ba252c6d40..5c6dab748e 100644
--- a/nailgun/nailgun/api/v1/handlers/capacity.py
+++ b/nailgun/nailgun/api/v1/handlers/capacity.py
@@ -26,7 +26,9 @@ import web
 from nailgun import objects
 
 from nailgun.api.v1.handlers.base import BaseHandler
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 from nailgun.task.manager import GenerateCapacityLogTaskManager
 
 
@@ -78,14 +80,17 @@ class CapacityLogHandler(BaseHandler):
         "report"
     )
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         capacity_log = objects.CapacityLog.get_latest()
         if not capacity_log:
             raise self.http(404)
         return self.render(capacity_log)
 
-    @content
+    @handle_errors
+    @validate
     def PUT(self):
         """Starts capacity data generation.
 
diff --git a/nailgun/nailgun/api/v1/handlers/cluster.py b/nailgun/nailgun/api/v1/handlers/cluster.py
index 370b507657..2e18ac990d 100644
--- a/nailgun/nailgun/api/v1/handlers/cluster.py
+++ b/nailgun/nailgun/api/v1/handlers/cluster.py
@@ -23,10 +23,12 @@ import web
 
 from nailgun.api.v1.handlers.base import BaseHandler
 from nailgun.api.v1.handlers.base import CollectionHandler
-from nailgun.api.v1.handlers.base import content
 from nailgun.api.v1.handlers.base import DeferredTaskHandler
+from nailgun.api.v1.handlers.base import handle_errors
 from nailgun.api.v1.handlers.base import OrchestratorDeploymentTasksHandler
+from nailgun.api.v1.handlers.base import serialize
 from nailgun.api.v1.handlers.base import SingleHandler
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.handlers.deployment_graph import \
     RelatedDeploymentGraphCollectionHandler
 from nailgun.api.v1.handlers.deployment_graph import \
@@ -55,7 +57,9 @@ class ClusterHandler(SingleHandler):
     single = objects.Cluster
     validator = ClusterValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, obj_id):
         """:returns: JSONized Cluster object.
 
@@ -79,9 +83,10 @@ class ClusterHandler(SingleHandler):
         except errors.NetworkTemplateCannotBeApplied as exc:
             raise self.http(400, exc.message)
 
-        return self.single.to_json(obj)
+        return self.single.to_dict(obj)
 
-    @content
+    @handle_errors
+    @validate
     def DELETE(self, obj_id):
         """:returns: {}
 
@@ -174,7 +179,9 @@ class ClusterAttributesHandler(BaseHandler):
 
     validator = ClusterAttributesValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id):
         """:returns: JSONized Cluster attributes.
 
@@ -206,7 +213,9 @@ class ClusterAttributesHandler(BaseHandler):
         # entity and PATCH method for changing its parts.
         return self.PATCH(cluster_id)
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PATCH(self, cluster_id):
         """:returns: JSONized Cluster attributes.
 
@@ -239,7 +248,9 @@ class ClusterAttributesDefaultsHandler(BaseHandler):
         "editable",
     )
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id):
         """:returns: JSONized default Cluster attributes.
 
@@ -253,7 +264,9 @@ class ClusterAttributesDefaultsHandler(BaseHandler):
             raise self.http(500, "No attributes found!")
         return {"editable": attrs}
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, cluster_id):
         """:returns: JSONized Cluster attributes.
 
@@ -290,7 +303,9 @@ class ClusterAttributesDefaultsHandler(BaseHandler):
 class ClusterAttributesDeployedHandler(BaseHandler):
     """Cluster deployed attributes handler"""
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id):
         """:returns: JSONized deployed Cluster editable attributes with plugins
 
@@ -312,7 +327,9 @@ class ClusterAttributesDeployedHandler(BaseHandler):
 class ClusterGeneratedData(BaseHandler):
     """Cluster generated data"""
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id):
         """:returns: JSONized cluster generated data
 
@@ -333,7 +350,9 @@ class ClusterPluginsDeploymentTasksHandler(BaseHandler):
     """Handler for cluster plugins merged deployment tasks serialization."""
     single = objects.Cluster
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, obj_id):
         """:returns: Deployment tasks
 
@@ -351,7 +370,9 @@ class ClusterReleaseDeploymentTasksHandler(BaseHandler):
     """Handler for cluster release deployment tasks serialization."""
     single = objects.Cluster
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, obj_id):
         """:returns: Deployment tasks
 
@@ -374,7 +395,9 @@ class VmwareAttributesHandler(BaseHandler):
 
     validator = VmwareAttributesValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id):
         """:returns: JSONized Cluster vmware attributes.
 
@@ -401,7 +424,9 @@ class VmwareAttributesHandler(BaseHandler):
 
         return self.render(attributes)
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, cluster_id):
         """:returns: JSONized Cluster vmware attributes.
 
@@ -442,7 +467,9 @@ class VmwareAttributesHandler(BaseHandler):
 class VmwareAttributesDefaultsHandler(BaseHandler):
     """Vmware default attributes handler"""
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id):
         """:returns: JSONized default Cluster vmware attributes.
 
diff --git a/nailgun/nailgun/api/v1/handlers/cluster_plugin_link.py b/nailgun/nailgun/api/v1/handlers/cluster_plugin_link.py
index ded80e11e1..66f82a13d1 100644
--- a/nailgun/nailgun/api/v1/handlers/cluster_plugin_link.py
+++ b/nailgun/nailgun/api/v1/handlers/cluster_plugin_link.py
@@ -15,7 +15,9 @@
 #    under the License.
 
 from nailgun.api.v1.handlers import base
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.validators import cluster_plugin_link
 from nailgun import errors
 from nailgun import objects
@@ -26,6 +28,9 @@ class ClusterPluginLinkHandler(base.SingleHandler):
     validator = cluster_plugin_link.ClusterPluginLinkValidator
     single = objects.ClusterPluginLink
 
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id, obj_id):
         """:returns: JSONized REST object.
 
@@ -35,9 +40,11 @@ class ClusterPluginLinkHandler(base.SingleHandler):
         self.get_object_or_404(objects.Cluster, cluster_id)
 
         obj = self.get_object_or_404(self.single, obj_id)
-        return self.single.to_json(obj)
+        return self.single.to_dict(obj)
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, cluster_id, obj_id):
         """:returns: JSONized REST object.
 
@@ -51,7 +58,7 @@ class ClusterPluginLinkHandler(base.SingleHandler):
             instance=obj
         )
         self.single.update(obj, data)
-        return self.single.to_json(obj)
+        return self.single.to_dict(obj)
 
     def PATCH(self, cluster_id, obj_id):
         """:returns: JSONized REST object.
@@ -62,7 +69,8 @@ class ClusterPluginLinkHandler(base.SingleHandler):
         """
         return self.PUT(cluster_id, obj_id)
 
-    @content
+    @handle_errors
+    @validate
     def DELETE(self, cluster_id, obj_id):
         """:returns: JSONized REST object.
 
@@ -79,7 +87,9 @@ class ClusterPluginLinkCollectionHandler(base.CollectionHandler):
     collection = objects.ClusterPluginLinkCollection
     validator = cluster_plugin_link.ClusterPluginLinkValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id):
         """:returns: Collection of JSONized ClusterPluginLink objects.
 
@@ -87,11 +97,12 @@ class ClusterPluginLinkCollectionHandler(base.CollectionHandler):
                * 404 (cluster not found in db)
         """
         self.get_object_or_404(objects.Cluster, cluster_id)
-        return self.collection.to_json(
+        return self.collection.to_list(
             self.collection.get_by_cluster_id(cluster_id)
         )
 
-    @content
+    @handle_errors
+    @validate
     def POST(self, cluster_id):
         """:returns: JSONized REST object.
 
diff --git a/nailgun/nailgun/api/v1/handlers/component.py b/nailgun/nailgun/api/v1/handlers/component.py
index 10c1f130da..5fb48de5be 100644
--- a/nailgun/nailgun/api/v1/handlers/component.py
+++ b/nailgun/nailgun/api/v1/handlers/component.py
@@ -14,15 +14,20 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from nailgun.api.v1.handlers import base
+from nailgun.api.v1.handlers.base import CollectionHandler
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 from nailgun.objects import Release
 from nailgun.objects.serializers.release import ComponentSerializer
 
 
-class ComponentCollectionHandler(base.CollectionHandler):
+class ComponentCollectionHandler(CollectionHandler):
     """Component collection handler"""
 
-    @base.content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, release_id):
         """:returns: JSONized component data for release and releated plugins.
 
diff --git a/nailgun/nailgun/api/v1/handlers/deployment_graph.py b/nailgun/nailgun/api/v1/handlers/deployment_graph.py
index fac04cf1e6..2d6ce06958 100644
--- a/nailgun/nailgun/api/v1/handlers/deployment_graph.py
+++ b/nailgun/nailgun/api/v1/handlers/deployment_graph.py
@@ -16,8 +16,10 @@
 
 from nailgun.api.v1.handlers.base import BaseHandler
 from nailgun.api.v1.handlers.base import CollectionHandler
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
 from nailgun.api.v1.handlers.base import SingleHandler
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.validators import deployment_graph as validators
 
 from nailgun import errors
@@ -35,7 +37,9 @@ class RelatedDeploymentGraphHandler(SingleHandler):
     single = objects.DeploymentGraph
     related = None  # related should be substituted during handler inheritance
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, obj_id, graph_type=None):
         """Get deployment graph.
 
@@ -54,12 +58,14 @@ class RelatedDeploymentGraphHandler(SingleHandler):
         obj = self.get_object_or_404(self.related, int(obj_id))
         deployment_graph = self.single.get_for_model(obj, graph_type)
         if deployment_graph:
-            return self.single.to_json(deployment_graph)
+            return self.single.to_dict(deployment_graph)
         else:
             raise self.http(404, "Graph with type: {0} is not defined".format(
                 graph_type))
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def POST(self, obj_id, graph_type=None):
         """Create deployment graph.
 
@@ -85,9 +91,11 @@ class RelatedDeploymentGraphHandler(SingleHandler):
         else:
             deployment_graph = self.single.create_for_model(
                 data, obj, graph_type=graph_type)
-            return self.single.to_json(deployment_graph)
+            return self.single.to_dict(deployment_graph)
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, obj_id, graph_type=None):
         """Update deployment graph.
 
@@ -109,12 +117,14 @@ class RelatedDeploymentGraphHandler(SingleHandler):
         deployment_graph = self.single.get_for_model(obj, graph_type)
         if deployment_graph:
             self.single.update(deployment_graph, data)
-            return self.single.to_json(deployment_graph)
+            return self.single.to_dict(deployment_graph)
         else:
             raise self.http(404, "Graph with type: {0} is not defined".format(
                 graph_type))
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PATCH(self, obj_id, graph_type=None):
         """Update deployment graph.
 
@@ -132,6 +142,8 @@ class RelatedDeploymentGraphHandler(SingleHandler):
         """
         return self.PUT(obj_id, graph_type)
 
+    @handle_errors
+    @validate
     def DELETE(self, obj_id, graph_type=None):
         """Delete deployment graph.
 
@@ -161,7 +173,9 @@ class RelatedDeploymentGraphCollectionHandler(CollectionHandler):
     collection = objects.DeploymentGraphCollection
     related = None  # related should be substituted during handler inheritance
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, obj_id):
         """Get deployment graphs list for given object.
 
@@ -176,7 +190,7 @@ class RelatedDeploymentGraphCollectionHandler(CollectionHandler):
         """
         related_model = self.get_object_or_404(self.related, int(obj_id))
         graphs = self.collection.get_for_model(related_model)
-        return self.collection.to_json(graphs)
+        return self.collection.to_list(graphs)
 
 
 class DeploymentGraphHandler(SingleHandler):
@@ -185,7 +199,8 @@ class DeploymentGraphHandler(SingleHandler):
     validator = validators.DeploymentGraphValidator
     single = objects.DeploymentGraph
 
-    @content
+    @handle_errors
+    @validate
     def DELETE(self, obj_id):
         """Delete deployment graph.
 
@@ -196,7 +211,6 @@ class DeploymentGraphHandler(SingleHandler):
         self.single.delete(d_e)
         raise self.http(204)
 
-    @content
     def PATCH(self, obj_id):
         return self.PUT(obj_id)
 
@@ -210,7 +224,8 @@ class GraphsExecutorHandler(BaseHandler):
 
     validator = validators.GraphExecuteParamsValidator
 
-    @content
+    @handle_errors
+    @validate
     def POST(self):
         """:returns: JSONized Task object.
 
diff --git a/nailgun/nailgun/api/v1/handlers/deployment_history.py b/nailgun/nailgun/api/v1/handlers/deployment_history.py
index fa0aab8685..7532af7193 100644
--- a/nailgun/nailgun/api/v1/handlers/deployment_history.py
+++ b/nailgun/nailgun/api/v1/handlers/deployment_history.py
@@ -15,7 +15,9 @@
 #    under the License.
 
 from nailgun.api.v1.handlers import base
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.validators.deployment_history import \
     DeploymentHistoryValidator
 from nailgun import errors
@@ -27,7 +29,9 @@ class DeploymentHistoryCollectionHandler(base.CollectionHandler):
     collection = objects.DeploymentHistoryCollection
     validator = DeploymentHistoryValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, transaction_id):
         """:returns: Collection of JSONized DeploymentHistory records.
 
diff --git a/nailgun/nailgun/api/v1/handlers/logs.py b/nailgun/nailgun/api/v1/handlers/logs.py
index 6e840f27cf..cd8bc9c2c4 100644
--- a/nailgun/nailgun/api/v1/handlers/logs.py
+++ b/nailgun/nailgun/api/v1/handlers/logs.py
@@ -32,7 +32,9 @@ from nailgun import consts
 from nailgun import objects
 
 from nailgun.api.v1.handlers.base import BaseHandler
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 from nailgun.settings import settings
 from nailgun.task.manager import DumpTaskManager
 from nailgun.task.task import DumpTask
@@ -195,7 +197,9 @@ def read_log(
 class LogEntryCollectionHandler(BaseHandler):
     """Log entry collection handler"""
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         """Receives following parameters:
 
@@ -382,7 +386,8 @@ class LogEntryCollectionHandler(BaseHandler):
 
 class LogPackageHandler(BaseHandler):
     """Log package handler"""
-    @content
+    @handle_errors
+    @validate
     def PUT(self):
         """:returns: JSONized Task object.
 
@@ -404,7 +409,9 @@ class LogPackageHandler(BaseHandler):
 
 class LogPackageDefaultConfig(BaseHandler):
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         """Generates default config for snapshot
 
@@ -416,7 +423,7 @@ class LogPackageDefaultConfig(BaseHandler):
 class LogSourceCollectionHandler(BaseHandler):
     """Log source collection handler"""
 
-    @content
+    @serialize
     def GET(self):
         """:returns: Collection of log sources (from settings)
 
@@ -443,7 +450,9 @@ class SnapshotDownloadHandler(BaseHandler):
 class LogSourceByNodeCollectionHandler(BaseHandler):
     """Log source by node collection handler"""
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, node_id):
         """:returns: Collection of log sources by node (from settings)
 
diff --git a/nailgun/nailgun/api/v1/handlers/master_node_settings.py b/nailgun/nailgun/api/v1/handlers/master_node_settings.py
index a6acf7d4b7..1f3f76f019 100644
--- a/nailgun/nailgun/api/v1/handlers/master_node_settings.py
+++ b/nailgun/nailgun/api/v1/handlers/master_node_settings.py
@@ -14,8 +14,9 @@
 
 from oslo_serialization import jsonutils
 
-from nailgun.api.v1.handlers.base import content
 from nailgun.api.v1.handlers.base import DBSingletonHandler
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.validators.master_node_settings \
     import MasterNodeSettingsValidator
 from nailgun.logger import logger
@@ -71,12 +72,14 @@ class MasterNodeSettingsHandler(DBSingletonHandler):
             self._handle_stats_opt_in(settings_data=jsonutils.loads(result))
         return result
 
-    @content
+    @handle_errors
+    @validate
     def PUT(self):
         return self._perform_update(
             super(MasterNodeSettingsHandler, self).PUT)
 
-    @content
+    @handle_errors
+    @validate
     def PATCH(self):
         return self._perform_update(
             super(MasterNodeSettingsHandler, self).PATCH)
diff --git a/nailgun/nailgun/api/v1/handlers/node.py b/nailgun/nailgun/api/v1/handlers/node.py
index eee7e7259e..ac488689c0 100644
--- a/nailgun/nailgun/api/v1/handlers/node.py
+++ b/nailgun/nailgun/api/v1/handlers/node.py
@@ -24,8 +24,10 @@ import web
 
 from nailgun.api.v1.handlers.base import BaseHandler
 from nailgun.api.v1.handlers.base import CollectionHandler
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
 from nailgun.api.v1.handlers.base import SingleHandler
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.validators import node as node_validators
 
 from nailgun import errors
@@ -44,7 +46,9 @@ class NodeHandler(SingleHandler):
     single = objects.Node
     validator = node_validators.NodeValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, obj_id):
         """:returns: JSONized Node object.
 
@@ -69,9 +73,10 @@ class NodeHandler(SingleHandler):
         except errors.NetworkTemplateCannotBeApplied as exc:
             raise self.http(400, exc.message)
 
-        return self.single.to_json(obj)
+        return self.single.to_dict(obj)
 
-    @content
+    @handle_errors
+    @validate
     def DELETE(self, obj_id):
         """Deletes a node from DB and from Cobbler.
 
@@ -100,7 +105,9 @@ class NodeCollectionHandler(CollectionHandler):
     validator = node_validators.NodeValidator
     collection = objects.NodeCollection
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         """May receive cluster_id parameter to filter list of nodes
 
@@ -115,9 +122,11 @@ class NodeCollectionHandler(CollectionHandler):
         elif cluster_id:
             nodes = nodes.filter_by(cluster_id=cluster_id)
 
-        return self.collection.to_json(nodes)
+        return self.collection.to_list(nodes)
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self):
         """:returns: Collection of JSONized Node objects.
 
@@ -147,9 +156,10 @@ class NodeCollectionHandler(CollectionHandler):
             self.collection.eager_nodes_handlers(None),
             nodes_updated
         )
-        return self.collection.to_json(nodes)
+        return self.collection.to_list(nodes)
 
-    @content
+    @handle_errors
+    @validate
     def DELETE(self):
         """Deletes a batch of nodes.
 
@@ -188,7 +198,9 @@ class NodeAgentHandler(BaseHandler):
     collection = objects.NodeCollection
     validator = node_validators.NodeValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self):
         """:returns: node id.
 
@@ -227,7 +239,9 @@ class NodeAgentHandler(BaseHandler):
 class NodesAllocationStatsHandler(BaseHandler):
     """Node allocation stats handler"""
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         """:returns: Total and unallocated nodes count.
 
@@ -245,7 +259,9 @@ class NodeAttributesHandler(BaseHandler):
 
     validator = node_validators.NodeAttributesValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, node_id):
         """:returns: JSONized Node attributes.
 
@@ -256,7 +272,9 @@ class NodeAttributesHandler(BaseHandler):
 
         return objects.Node.get_attributes(node)
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, node_id):
         """:returns: JSONized Node attributes.
 
diff --git a/nailgun/nailgun/api/v1/handlers/node_group.py b/nailgun/nailgun/api/v1/handlers/node_group.py
index 657372f982..5539a6ce96 100644
--- a/nailgun/nailgun/api/v1/handlers/node_group.py
+++ b/nailgun/nailgun/api/v1/handlers/node_group.py
@@ -21,9 +21,10 @@ Handlers dealing with node groups
 import web
 
 from nailgun.api.v1.handlers.base import CollectionHandler
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
 from nailgun.api.v1.handlers.base import SingleHandler
-
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.validators.node_group import NodeGroupValidator
 
 from nailgun import errors
@@ -35,7 +36,8 @@ class NodeGroupHandler(SingleHandler):
     single = objects.NodeGroup
     validator = NodeGroupValidator
 
-    @content
+    @handle_errors
+    @validate
     def DELETE(self, group_id):
         """:returns: {}
 
@@ -67,7 +69,9 @@ class NodeGroupCollectionHandler(CollectionHandler):
     collection = objects.NodeGroupCollection
     validator = NodeGroupValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         """May receive cluster_id parameter to filter list of groups
 
@@ -78,10 +82,10 @@ class NodeGroupCollectionHandler(CollectionHandler):
         user_data = web.input(cluster_id=None)
 
         if user_data.cluster_id is not None:
-            return self.collection.to_json(
+            return self.collection.to_list(
                 self.collection.get_by_cluster_id(
                     user_data.cluster_id
                 )
             )
         else:
-            return self.collection.to_json()
+            return self.collection.to_list()
diff --git a/nailgun/nailgun/api/v1/handlers/notifications.py b/nailgun/nailgun/api/v1/handlers/notifications.py
index 2991720af8..6113c8fd89 100644
--- a/nailgun/nailgun/api/v1/handlers/notifications.py
+++ b/nailgun/nailgun/api/v1/handlers/notifications.py
@@ -24,7 +24,9 @@ from nailgun.api.v1.handlers.base import SingleHandler
 
 from nailgun import objects
 
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.validators.notification import NotificationValidator
 
 
@@ -40,7 +42,9 @@ class NotificationCollectionHandler(CollectionHandler):
     collection = objects.NotificationCollection
     validator = NotificationValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self):
         """:returns: Collection of JSONized Notification objects.
 
@@ -54,4 +58,4 @@ class NotificationCollectionHandler(CollectionHandler):
             notif = self.collection.single.get_by_uid(nd["id"])
             self.collection.single.update(notif, nd)
             notifications_updated.append(notif)
-        return self.collection.to_json(notifications_updated)
+        return self.collection.to_list(notifications_updated)
diff --git a/nailgun/nailgun/api/v1/handlers/openstack_config.py b/nailgun/nailgun/api/v1/handlers/openstack_config.py
index 8a95e9f04f..7cd89d1483 100644
--- a/nailgun/nailgun/api/v1/handlers/openstack_config.py
+++ b/nailgun/nailgun/api/v1/handlers/openstack_config.py
@@ -18,8 +18,10 @@ import six
 import web
 
 from nailgun.api.v1.handlers.base import BaseHandler
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
 from nailgun.api.v1.handlers.base import SingleHandler
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.validators.openstack_config import OpenstackConfigValidator
 from nailgun import errors
 from nailgun.logger import logger
@@ -31,7 +33,9 @@ class OpenstackConfigCollectionHandler(BaseHandler):
 
     validator = OpenstackConfigValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         """Returns list of filtered config objects.
 
@@ -48,7 +52,8 @@ class OpenstackConfigCollectionHandler(BaseHandler):
                 configs, 'node_id', node_ids)
         return objects.OpenstackConfigCollection.to_list(configs)
 
-    @content
+    @handle_errors
+    @validate
     def POST(self):
         """Creates new config object.
 
@@ -72,7 +77,8 @@ class OpenstackConfigHandler(SingleHandler):
     single = objects.OpenstackConfig
     validator = OpenstackConfigValidator
 
-    @content
+    @handle_errors
+    @validate
     def PUT(self, obj_id):
         """Update an existing configuration is not allowed
 
@@ -80,7 +86,8 @@ class OpenstackConfigHandler(SingleHandler):
         """
         raise self.http(405)
 
-    @content
+    @handle_errors
+    @validate
     def DELETE(self, obj_id):
         """:returns: Empty string
 
@@ -111,7 +118,8 @@ class OpenstackConfigExecuteHandler(BaseHandler):
     validator = OpenstackConfigValidator
     task_manager = OpenstackConfigTaskManager
 
-    @content
+    @handle_errors
+    @validate
     def PUT(self):
         """Executes update tasks for specified resources.
 
diff --git a/nailgun/nailgun/api/v1/handlers/orchestrator.py b/nailgun/nailgun/api/v1/handlers/orchestrator.py
index bf2d66a0e3..c26a403f04 100644
--- a/nailgun/nailgun/api/v1/handlers/orchestrator.py
+++ b/nailgun/nailgun/api/v1/handlers/orchestrator.py
@@ -20,7 +20,9 @@ import six
 import web
 
 from nailgun.api.v1.handlers.base import BaseHandler
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.validators.cluster import ProvisionSelectedNodesValidator
 from nailgun.api.v1.validators.node import DeploySelectedNodesValidator
 from nailgun.api.v1.validators.node import NodeDeploymentValidator
@@ -79,7 +81,9 @@ class DefaultOrchestratorInfo(NodesFilterMixin, BaseHandler):
     Need to redefine serializer variable
     """
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id):
         """:returns: JSONized default data which will be passed to orchestrator
 
@@ -110,7 +114,9 @@ class OrchestratorInfo(BaseHandler):
         """Method should override data which will be passed to orchestrator"""
         raise NotImplementedError('Please Implement this method')
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id):
         """:returns: JSONized data which will be passed to orchestrator
 
@@ -120,7 +126,9 @@ class OrchestratorInfo(BaseHandler):
         cluster = self.get_object_or_404(objects.Cluster, cluster_id)
         return self.get_orchestrator_info(cluster)
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, cluster_id):
         """:returns: JSONized data which will be passed to orchestrator
 
@@ -136,7 +144,8 @@ class OrchestratorInfo(BaseHandler):
                      .format(cluster_id))
         return data
 
-    @content
+    @handle_errors
+    @validate
     def DELETE(self, cluster_id):
         """:returns: {}
 
@@ -235,7 +244,8 @@ class SelectedNodesBase(NodesFilterMixin, BaseHandler):
 
         self.raise_task(task)
 
-    @content
+    @handle_errors
+    @validate
     def PUT(self, cluster_id):
         """:returns: JSONized Task object.
 
@@ -257,7 +267,8 @@ class ProvisionSelectedNodes(SelectedNodesBase):
     def get_default_nodes(self, cluster):
         return TaskHelper.nodes_to_provision(cluster)
 
-    @content
+    @handle_errors
+    @validate
     def PUT(self, cluster_id):
         """:returns: JSONized Task object.
 
@@ -303,7 +314,8 @@ class BaseDeploySelectedNodes(SelectedNodesBase):
 class DeploySelectedNodes(BaseDeploySelectedNodes, DryRunMixin):
     """Handler for deployment selected nodes."""
 
-    @content
+    @handle_errors
+    @validate
     def PUT(self, cluster_id):
         """:returns: JSONized Task object.
 
@@ -324,7 +336,8 @@ class DeploySelectedNodesWithTasks(BaseDeploySelectedNodes, DryRunMixin):
 
     validator = NodeDeploymentValidator
 
-    @content
+    @handle_errors
+    @validate
     def PUT(self, cluster_id):
         """:returns: JSONized Task object.
 
@@ -353,6 +366,8 @@ class TaskDeployGraph(BaseHandler):
 
     validator = GraphSolverVisualizationValidator
 
+    @handle_errors
+    @validate
     def GET(self, cluster_id):
         """:returns: DOT representation of deployment graph.
 
@@ -407,7 +422,9 @@ class SerializedTasksHandler(NodesFilterMixin, BaseHandler):
             return objects.Cluster.get_nodes_not_for_deletion(cluster).all()
         return TaskHelper.nodes_to_deploy(cluster)
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id):
         """:returns: serialized tasks in json format
 
diff --git a/nailgun/nailgun/api/v1/handlers/plugin.py b/nailgun/nailgun/api/v1/handlers/plugin.py
index 14c0348c34..f41f58905d 100644
--- a/nailgun/nailgun/api/v1/handlers/plugin.py
+++ b/nailgun/nailgun/api/v1/handlers/plugin.py
@@ -17,7 +17,8 @@
 import six
 
 from nailgun.api.v1.handlers import base
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.handlers.deployment_graph import \
     RelatedDeploymentGraphCollectionHandler
 from nailgun.api.v1.handlers.deployment_graph import \
@@ -39,7 +40,8 @@ class PluginCollectionHandler(base.CollectionHandler):
     collection = objects.PluginCollection
     validator = plugin.PluginValidator
 
-    @content
+    @handle_errors
+    @validate
     def POST(self):
         """:returns: JSONized REST object.
 
@@ -59,7 +61,8 @@ class PluginSyncHandler(base.BaseHandler):
 
     validator = plugin.PluginSyncValidator
 
-    @content
+    @handle_errors
+    @validate
     def POST(self):
         """:returns: JSONized REST object.
 
diff --git a/nailgun/nailgun/api/v1/handlers/plugin_link.py b/nailgun/nailgun/api/v1/handlers/plugin_link.py
index a51c579485..2cd97d8cdd 100644
--- a/nailgun/nailgun/api/v1/handlers/plugin_link.py
+++ b/nailgun/nailgun/api/v1/handlers/plugin_link.py
@@ -15,7 +15,9 @@
 #    under the License.
 
 from nailgun.api.v1.handlers import base
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.validators import plugin_link
 from nailgun import errors
 from nailgun import objects
@@ -36,6 +38,9 @@ class PluginLinkHandler(base.SingleHandler):
                 "Plugin with id {0} not found".format(plugin_id)
             )
 
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, plugin_id, obj_id):
         """:returns: JSONized REST object.
 
@@ -43,9 +48,11 @@ class PluginLinkHandler(base.SingleHandler):
                * 404 (dashboard entry not found in db)
         """
         obj = self._get_plugin_link_object(plugin_id, obj_id)
-        return self.single.to_json(obj)
+        return self.single.to_dict(obj)
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, plugin_id, obj_id):
         """:returns: JSONized REST object.
 
@@ -58,7 +65,7 @@ class PluginLinkHandler(base.SingleHandler):
             self.validator.validate_update,
             instance=obj)
         self.single.update(obj, data)
-        return self.single.to_json(obj)
+        return self.single.to_dict(obj)
 
     def PATCH(self, plugin_id, obj_id):
         """:returns: JSONized REST object.
@@ -69,7 +76,8 @@ class PluginLinkHandler(base.SingleHandler):
         """
         return self.PUT(plugin_id, obj_id)
 
-    @content
+    @handle_errors
+    @validate
     def DELETE(self, plugin_id, obj_id):
         """:returns: JSONized REST object.
 
@@ -86,7 +94,8 @@ class PluginLinkCollectionHandler(base.CollectionHandler):
     collection = objects.PluginLinkCollection
     validator = plugin_link.PluginLinkValidator
 
-    @content
+    @handle_errors
+    @validate
     def GET(self, plugin_id):
         """:returns: Collection of JSONized PluginLink objects.
 
@@ -94,11 +103,12 @@ class PluginLinkCollectionHandler(base.CollectionHandler):
                * 404 (plugin not found in db)
         """
         self.get_object_or_404(objects.Plugin, plugin_id)
-        return self.collection.to_json(
+        return self.collection.to_list(
             self.collection.get_by_plugin_id(plugin_id)
         )
 
-    @content
+    @handle_errors
+    @validate
     def POST(self, plugin_id):
         """:returns: JSONized REST object.
 
diff --git a/nailgun/nailgun/api/v1/handlers/release.py b/nailgun/nailgun/api/v1/handlers/release.py
index 94efdcc5f9..155b97e0e5 100644
--- a/nailgun/nailgun/api/v1/handlers/release.py
+++ b/nailgun/nailgun/api/v1/handlers/release.py
@@ -19,9 +19,11 @@ Handlers dealing with releases
 """
 
 from nailgun.api.v1.handlers.base import CollectionHandler
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
 from nailgun.api.v1.handlers.base import OrchestratorDeploymentTasksHandler
+from nailgun.api.v1.handlers.base import serialize
 from nailgun.api.v1.handlers.base import SingleHandler
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.handlers.deployment_graph import \
     RelatedDeploymentGraphCollectionHandler
 from nailgun.api.v1.handlers.deployment_graph import \
@@ -47,7 +49,9 @@ class ReleaseAttributesMetadataHandler(SingleHandler):
     single = Release
     validator = ReleaseAttributesMetadataValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, obj_id):
         """:returns: JSONized Release attributes metadata.
 
@@ -57,7 +61,9 @@ class ReleaseAttributesMetadataHandler(SingleHandler):
         release = self.get_object_or_404(self.single, obj_id)
         return release['attributes_metadata']
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, obj_id):
         """:returns: JSONized Release attributes metadata.
 
@@ -77,14 +83,16 @@ class ReleaseCollectionHandler(CollectionHandler):
     validator = ReleaseValidator
     collection = ReleaseCollection
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         """:returns: Sorted releases' collection in JSON format
 
         :http: * 200 (OK)
         """
         q = sorted(self.collection.all(), reverse=True)
-        return self.collection.to_json(q)
+        return self.collection.to_list(q)
 
 
 class ReleaseNetworksHandler(SingleHandler):
@@ -93,7 +101,9 @@ class ReleaseNetworksHandler(SingleHandler):
     single = Release
     validator = ReleaseNetworksValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, obj_id):
         """Read release networks metadata
 
@@ -105,7 +115,9 @@ class ReleaseNetworksHandler(SingleHandler):
         obj = self.get_object_or_404(self.single, obj_id)
         return obj['networks_metadata']
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, obj_id):
         """Updates release networks metadata
 
diff --git a/nailgun/nailgun/api/v1/handlers/removed.py b/nailgun/nailgun/api/v1/handlers/removed.py
index cadbbf15a9..cae367d5fe 100644
--- a/nailgun/nailgun/api/v1/handlers/removed.py
+++ b/nailgun/nailgun/api/v1/handlers/removed.py
@@ -17,7 +17,9 @@
 Handlers for removed resources
 """
 from nailgun.api.v1.handlers.base import BaseHandler
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 
 
 class BaseRemovedInHandler(BaseHandler):
@@ -27,7 +29,9 @@ class BaseRemovedInHandler(BaseHandler):
     def fuel_version(self):
         raise NotImplementedError
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         """A stub for the request. Always returns 410 with removed message.
 
diff --git a/nailgun/nailgun/api/v1/handlers/role.py b/nailgun/nailgun/api/v1/handlers/role.py
index 4e2cb4f9d0..382517776f 100644
--- a/nailgun/nailgun/api/v1/handlers/role.py
+++ b/nailgun/nailgun/api/v1/handlers/role.py
@@ -17,7 +17,9 @@
 import six
 
 from nailgun.api.v1.handlers import base
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.validators.role import RoleValidator
 from nailgun import errors
 from nailgun import objects
@@ -37,7 +39,9 @@ class RoleHandler(base.SingleHandler):
                     release=release_id, name=role_name))
         return role
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, release_id, role_name):
         """Retrieve role
 
@@ -48,7 +52,9 @@ class RoleHandler(base.SingleHandler):
         release = self.get_object_or_404(objects.Release, release_id)
         return RoleSerializer.serialize_from_release(release, role_name)
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, release_id, role_name):
         """Update role
 
@@ -85,7 +91,8 @@ class RoleCollectionHandler(base.CollectionHandler):
 
     validator = RoleValidator
 
-    @content
+    @handle_errors
+    @validate
     def POST(self, release_id):
         """Create role for release
 
@@ -110,7 +117,9 @@ class RoleCollectionHandler(base.CollectionHandler):
         raise self.http(
             201, RoleSerializer.serialize_from_release(release, role_name))
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, release_id):
         release = self.get_object_or_404(objects.Release, release_id)
         role_names = six.iterkeys(release.roles_metadata)
@@ -125,7 +134,9 @@ class ClusterRolesHandler(base.BaseHandler):
         if role_name not in available_roles:
             raise self.http(404, 'Role is not found for the cluster')
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id, role_name):
         """:returns: JSON-ed metadata for the role
 
@@ -140,7 +151,9 @@ class ClusterRolesHandler(base.BaseHandler):
 
 class ClusterRolesCollectionHandler(base.BaseHandler):
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id):
         """:returns: collection of JSON-ed cluster roles metadata
 
diff --git a/nailgun/nailgun/api/v1/handlers/tasks.py b/nailgun/nailgun/api/v1/handlers/tasks.py
index 695a015826..5268592e5f 100644
--- a/nailgun/nailgun/api/v1/handlers/tasks.py
+++ b/nailgun/nailgun/api/v1/handlers/tasks.py
@@ -18,7 +18,9 @@ import web
 from nailgun.api.v1.handlers.base import CollectionHandler
 from nailgun.api.v1.handlers.base import SingleHandler
 
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.validators.task import TaskValidator
 
 from nailgun import errors
@@ -38,7 +40,8 @@ class TaskHandler(SingleHandler):
     single = objects.Task
     validator = TaskValidator
 
-    @content
+    @handle_errors
+    @validate
     def DELETE(self, obj_id):
         """:returns: Empty string
 
@@ -68,7 +71,9 @@ class TaskCollectionHandler(CollectionHandler):
     collection = objects.TaskCollection
     validator = TaskValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         """May receive cluster_id parameter to filter list of tasks
 
@@ -79,8 +84,8 @@ class TaskCollectionHandler(CollectionHandler):
         cluster_id = web.input(cluster_id=None).cluster_id
 
         if cluster_id is not None:
-            return self.collection.to_json(
+            return self.collection.to_list(
                 self.collection.get_by_cluster_id(cluster_id)
             )
         else:
-            return self.collection.to_json(self.collection.all_not_deleted())
+            return self.collection.to_list(self.collection.all_not_deleted())
diff --git a/nailgun/nailgun/api/v1/handlers/transactions.py b/nailgun/nailgun/api/v1/handlers/transactions.py
index 2ebf223284..703fe17e1a 100644
--- a/nailgun/nailgun/api/v1/handlers/transactions.py
+++ b/nailgun/nailgun/api/v1/handlers/transactions.py
@@ -18,7 +18,9 @@ import web
 from nailgun.api.v1.handlers.base import CollectionHandler
 from nailgun.api.v1.handlers.tasks import TaskHandler
 
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.validators.transaction import TransactionValidator
 
 from nailgun import errors
@@ -42,7 +44,9 @@ class TransactionCollectionHandler(CollectionHandler):
     collection = objects.TransactionCollection
     validator = TransactionValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         """May receive cluster_id parameter to filter list of tasks
 
@@ -60,7 +64,7 @@ class TransactionCollectionHandler(CollectionHandler):
         except errors.InvalidData as exc:
             raise self.http(400, exc.message)
 
-        return self.collection.to_json(
+        return self.collection.to_list(
             self.collection.get_transactions(
                 cluster_id=cluster_id,
                 statuses=statuses,
@@ -72,7 +76,9 @@ class BaseTransactionDataHandler(TransactionHandler):
 
     get_data = None
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, transaction_id):
         """:returns: Collection of JSONized DeploymentInfo objects.
 
diff --git a/nailgun/nailgun/api/v1/handlers/version.py b/nailgun/nailgun/api/v1/handlers/version.py
index 975678abc0..5b21a11a3a 100644
--- a/nailgun/nailgun/api/v1/handlers/version.py
+++ b/nailgun/nailgun/api/v1/handlers/version.py
@@ -19,14 +19,18 @@ Product info handlers
 """
 
 from nailgun.api.v1.handlers.base import BaseHandler
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 from nailgun.settings import settings
 
 
 class VersionHandler(BaseHandler):
     """Version info handler"""
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         """:returns: FUEL/FUELWeb commit SHA, release version.
 
diff --git a/nailgun/nailgun/api/v1/handlers/vms.py b/nailgun/nailgun/api/v1/handlers/vms.py
index 1022ce7b14..5a7d0551c0 100644
--- a/nailgun/nailgun/api/v1/handlers/vms.py
+++ b/nailgun/nailgun/api/v1/handlers/vms.py
@@ -20,7 +20,9 @@ import six
 import web
 
 from nailgun.api.v1.handlers.base import BaseHandler
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 from nailgun.api.v1.validators import node as validators
 
 from nailgun.logger import logger
@@ -72,7 +74,8 @@ class SpawnVmsHandler(BaseHandler):
         else:
             raise self.http(400, "No VMs to spawn")
 
-    @content
+    @handle_errors
+    @validate
     def PUT(self, cluster_id):
         """:returns: JSONized Task object.
 
@@ -93,7 +96,9 @@ class NodeVMsHandler(BaseHandler):
 
     validator = validators.NodeVMsValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, node_id):
         """:returns: JSONized node vms_conf.
 
@@ -104,7 +109,9 @@ class NodeVMsHandler(BaseHandler):
         node_vms = node.vms_conf
         return {"vms_conf": node_vms}
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, node_id):
         """:returns: JSONized node vms_conf.
 
diff --git a/nailgun/nailgun/extensions/network_manager/handlers/network_configuration.py b/nailgun/nailgun/extensions/network_manager/handlers/network_configuration.py
index afb257f69c..21b0c5bf2f 100644
--- a/nailgun/nailgun/extensions/network_manager/handlers/network_configuration.py
+++ b/nailgun/nailgun/extensions/network_manager/handlers/network_configuration.py
@@ -19,7 +19,9 @@ Handlers dealing with network configurations
 """
 from ..task.manager import UpdateDnsmasqTaskManager
 from nailgun.api.v1.handlers.base import BaseHandler
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 
 from nailgun.extensions.network_manager.objects.serializers.\
     network_configuration import NeutronNetworkConfigurationSerializer
@@ -71,7 +73,9 @@ class ProviderHandler(BaseHandler):
             cluster=cluster, networks_required=False)
         return cluster, data
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id):
         """:returns: JSONized network configuration for cluster.
 
@@ -91,7 +95,9 @@ class ProviderHandler(BaseHandler):
             logger.exception('Serialization failed')
             raise
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, cluster_id):
         """:returns: JSONized network configuration for cluster.
 
@@ -153,7 +159,9 @@ class TemplateNetworkConfigurationHandler(BaseHandler):
             raise self.http(403, "Network template cannot be changed "
                                  "during deployment and after upgrade.")
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id):
         """:returns: network template for cluster (json format)
 
@@ -163,7 +171,8 @@ class TemplateNetworkConfigurationHandler(BaseHandler):
         cluster = self.get_object_or_404(objects.Cluster, cluster_id)
         return cluster.network_config.configuration_template
 
-    @content
+    @handle_errors
+    @validate
     def PUT(self, cluster_id):
         """:returns: {}
 
@@ -202,7 +211,8 @@ class NetworkConfigurationVerifyHandler(ProviderHandler):
 
     validator = NetworkConfigurationValidator
 
-    @content
+    @handle_errors
+    @validate
     def PUT(self, cluster_id):
         """:IMPORTANT: this method should be rewritten to be more RESTful
 
@@ -252,7 +262,9 @@ class NeutronNetworkConfigurationVerifyHandler(
 class NetworkAttributesDeployedHandler(BaseHandler):
     """Cluster deployed network attributes handler"""
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id):
         """:returns: JSONized deployed Cluster network configuration.
 
diff --git a/nailgun/nailgun/extensions/network_manager/handlers/network_group.py b/nailgun/nailgun/extensions/network_manager/handlers/network_group.py
index 27189e8b0f..55c3700bfe 100644
--- a/nailgun/nailgun/extensions/network_manager/handlers/network_group.py
+++ b/nailgun/nailgun/extensions/network_manager/handlers/network_group.py
@@ -15,8 +15,10 @@
 #    under the License.
 
 from nailgun.api.v1.handlers.base import CollectionHandler
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
 from nailgun.api.v1.handlers.base import SingleHandler
+from nailgun.api.v1.handlers.base import validate
 from nailgun.extensions.network_manager.validators.network import \
     NetworkGroupValidator
 
@@ -38,7 +40,9 @@ class NetworkGroupHandler(SingleHandler):
     validator = NetworkGroupValidator
     single = objects.NetworkGroup
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, group_id):
         """:returns: JSONized Network Group object.
 
@@ -57,9 +61,10 @@ class NetworkGroupHandler(SingleHandler):
         )
         self.single.update(ng, data)
 
-        return self.single.to_json(ng)
+        return self.single.to_dict(ng)
 
-    @content
+    @handle_errors
+    @validate
     def DELETE(self, group_id):
         """Remove Network Group
 
@@ -87,7 +92,8 @@ class NetworkGroupCollectionHandler(CollectionHandler):
     collection = objects.NetworkGroupCollection
     validator = NetworkGroupValidator
 
-    @content
+    @handle_errors
+    @validate
     def POST(self):
         """:returns: JSONized Network Group object.
 
diff --git a/nailgun/nailgun/extensions/network_manager/handlers/nic.py b/nailgun/nailgun/extensions/network_manager/handlers/nic.py
index 586c879efa..38028a62f7 100644
--- a/nailgun/nailgun/extensions/network_manager/handlers/nic.py
+++ b/nailgun/nailgun/extensions/network_manager/handlers/nic.py
@@ -21,7 +21,9 @@ Handlers dealing with nodes
 import web
 
 from nailgun.api.v1.handlers.base import BaseHandler
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 from nailgun.extensions.network_manager.validators.network import \
     NetAssignmentValidator
 
@@ -42,7 +44,9 @@ class NodeNICsHandler(BaseHandler):
     validator = NetAssignmentValidator
     serializer = NodeInterfacesSerializer
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, node_id):
         """:returns: Collection of JSONized Node interfaces.
 
@@ -52,7 +56,9 @@ class NodeNICsHandler(BaseHandler):
         node = self.get_object_or_404(objects.Node, node_id)
         return map(self.render, node.interfaces)
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, node_id):
         """:returns: Collection of JSONized Node objects.
 
@@ -79,7 +85,9 @@ class NodeCollectionNICsHandler(BaseHandler):
     validator = NetAssignmentValidator
     serializer = NodeInterfacesSerializer
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self):
         """:returns: Collection of JSONized Node objects.
 
@@ -107,7 +115,9 @@ class NodeCollectionNICsHandler(BaseHandler):
 class NodeNICsDefaultHandler(BaseHandler):
     """Node default network interfaces handler"""
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, node_id):
         """:returns: Collection of default JSONized interfaces for node.
 
@@ -129,7 +139,9 @@ class NodeCollectionNICsDefaultHandler(NodeNICsDefaultHandler):
 
     validator = NetAssignmentValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         """May receive cluster_id parameter to filter list of nodes
 
diff --git a/nailgun/nailgun/extensions/network_manager/handlers/vip.py b/nailgun/nailgun/extensions/network_manager/handlers/vip.py
index 61b063b927..f46d38132e 100644
--- a/nailgun/nailgun/extensions/network_manager/handlers/vip.py
+++ b/nailgun/nailgun/extensions/network_manager/handlers/vip.py
@@ -18,7 +18,9 @@
 import web
 
 from nailgun.api.v1.handlers import base
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 from nailgun.extensions.network_manager.validators import ip_addr
 from nailgun import objects
 
@@ -51,7 +53,9 @@ class ClusterVIPHandler(base.SingleHandler):
         else:
             return obj
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id, ip_addr_id):
         """Get VIP record.
 
@@ -68,9 +72,11 @@ class ClusterVIPHandler(base.SingleHandler):
         """
         obj = self._get_vip_from_cluster_or_http_error(
             int(cluster_id), int(ip_addr_id))
-        return self.single.to_json(obj)
+        return self.single.to_dict(obj)
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, cluster_id, ip_addr_id):
         """Update VIP record.
 
@@ -94,7 +100,7 @@ class ClusterVIPHandler(base.SingleHandler):
             existing_obj=obj
         )
         self.single.update(obj, data)
-        return self.single.to_json(obj)
+        return self.single.to_dict(obj)
 
     def PATCH(self, cluster_id, ip_addr_id):
         """Update VIP record.
@@ -126,7 +132,9 @@ class ClusterVIPCollectionHandler(base.CollectionHandler):
     collection = objects.IPAddrCollection
     validator = ip_addr.IPAddrValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, cluster_id):
         """Get VIPs collection optionally filtered by network or network role.
 
@@ -141,7 +149,7 @@ class ClusterVIPCollectionHandler(base.CollectionHandler):
         network_role = web.input(network_role=None).network_role
 
         self.get_object_or_404(objects.Cluster, int(cluster_id))
-        return self.collection.to_json(
+        return self.collection.to_list(
             self.collection.get_vips_by_cluster_id(
                 int(cluster_id),
                 network_id,
@@ -149,7 +157,8 @@ class ClusterVIPCollectionHandler(base.CollectionHandler):
             )
         )
 
-    @content
+    @handle_errors
+    @validate
     def POST(self, cluster_id):
         """Create (allocate) VIP
 
@@ -174,7 +183,9 @@ class ClusterVIPCollectionHandler(base.CollectionHandler):
 
         raise self.http(200, self.collection.single.to_json(vip))
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, cluster_id):
         """Update VIPs collection.
 
@@ -191,7 +202,7 @@ class ClusterVIPCollectionHandler(base.CollectionHandler):
             cluster_id=int(cluster_id)
         )
 
-        return self.collection.to_json(
+        return self.collection.to_list(
             self.collection.update_vips(update_data)
         )
 
diff --git a/nailgun/nailgun/extensions/volume_manager/handlers/disks.py b/nailgun/nailgun/extensions/volume_manager/handlers/disks.py
index 1a6597cecf..079be485c8 100644
--- a/nailgun/nailgun/extensions/volume_manager/handlers/disks.py
+++ b/nailgun/nailgun/extensions/volume_manager/handlers/disks.py
@@ -22,7 +22,9 @@ from ..manager import DisksFormatConvertor
 from ..manager import VolumeManager
 from ..validators.disks import NodeDisksValidator
 from nailgun.api.v1.handlers.base import BaseHandler
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 from nailgun import objects
 
 
@@ -30,7 +32,9 @@ class NodeDisksHandler(BaseHandler):
 
     validator = NodeDisksValidator
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, node_id):
         """:returns: JSONized node disks.
 
@@ -43,7 +47,9 @@ class NodeDisksHandler(BaseHandler):
         node_volumes = VolumeObject.get_volumes(node)
         return DisksFormatConvertor.format_disks_to_simple(node_volumes)
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def PUT(self, node_id):
         """:returns: JSONized node disks.
 
@@ -75,7 +81,9 @@ class NodeDisksHandler(BaseHandler):
 
 class NodeDefaultsDisksHandler(BaseHandler):
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, node_id):
         """:returns: JSONized node disks.
 
@@ -92,7 +100,9 @@ class NodeDefaultsDisksHandler(BaseHandler):
 
 class NodeVolumesInformationHandler(BaseHandler):
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self, node_id):
         """:returns: JSONized volumes info for node.
 
diff --git a/nailgun/nailgun/fake_keystone/handlers.py b/nailgun/nailgun/fake_keystone/handlers.py
index 535dfd0f44..41e528cb81 100644
--- a/nailgun/nailgun/fake_keystone/handlers.py
+++ b/nailgun/nailgun/fake_keystone/handlers.py
@@ -15,7 +15,9 @@
 #    under the License.
 
 from nailgun.api.v1.handlers.base import BaseHandler
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
+from nailgun.api.v1.handlers.base import validate
 from nailgun.fake_keystone import generate_token
 from nailgun.fake_keystone import validate_password_credentials
 from nailgun.fake_keystone import validate_token
@@ -24,7 +26,9 @@ from nailgun.settings import settings
 
 class TokensHandler(BaseHandler):
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def POST(self):
         data = self.checked_data()
         try:
@@ -73,7 +77,9 @@ class TokensHandler(BaseHandler):
 
 class VersionHandler(BaseHandler):
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         keystone_href = 'http://{ip_addr}:{port}/keystone/v2.0/'.format(
             ip_addr=settings.LISTEN_ADDRESS, port=settings.LISTEN_PORT)
@@ -107,7 +113,9 @@ class VersionHandler(BaseHandler):
 
 class ServicesHandler(BaseHandler):
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         return {
             'OS-KSADM:services': [{'type': 'ostf', 'enabled': True,
@@ -127,7 +135,9 @@ class ServicesHandler(BaseHandler):
 
 class EndpointsHandler(BaseHandler):
 
-    @content
+    @handle_errors
+    @validate
+    @serialize
     def GET(self):
         keystone_href = 'http://{ip_addr}:{port}/keystone/v2.0'.format(
             ip_addr=settings.AUTH['auth_host'], port=settings.LISTEN_PORT)
diff --git a/nailgun/nailgun/test/integration/test_graph_related_handlers.py b/nailgun/nailgun/test/integration/test_graph_related_handlers.py
index 218ad69415..f9aa4b430e 100644
--- a/nailgun/nailgun/test/integration/test_graph_related_handlers.py
+++ b/nailgun/nailgun/test/integration/test_graph_related_handlers.py
@@ -636,6 +636,8 @@ class TestStartEndTaskPassedCorrectly(BaseGraphTasksTests):
     def assert_passed_correctly(self, url, **kwargs):
         with mock.patch.object(GraphSolver,
                                'find_subgraph') as mfind_subgraph:
+            mfind_subgraph.return_value.node.values.return_value = {}
+
             resp = self.app.get(
                 url,
                 params=kwargs,
diff --git a/nailgun/nailgun/test/unit/test_handlers.py b/nailgun/nailgun/test/unit/test_handlers.py
index 2f6e02add5..428ac1760a 100644
--- a/nailgun/nailgun/test/unit/test_handlers.py
+++ b/nailgun/nailgun/test/unit/test_handlers.py
@@ -19,10 +19,9 @@ import urllib
 
 import web
 
-from mock import patch
-
 from nailgun.api.v1.handlers.base import BaseHandler
-from nailgun.api.v1.handlers.base import content
+from nailgun.api.v1.handlers.base import handle_errors
+from nailgun.api.v1.handlers.base import serialize
 
 from nailgun.test.base import BaseIntegrationTest
 from nailgun.utils import reverse
@@ -97,15 +96,15 @@ class TestHandlers(BaseIntegrationTest):
 
     def test_content_decorator(self):
 
-        class FakeHandler(object):
+        class FakeHandler(BaseHandler):
 
-            @content
+            @serialize
             def GET(self):
                 return {}
 
-            @content(["text/plain"])
+            @serialize
             def POST(self):
-                return "Plain Text"
+                return {}
 
         web.ctx.headers = []
         web.ctx.env = {"HTTP_ACCEPT": "text/html"}
@@ -116,18 +115,7 @@ class TestHandlers(BaseIntegrationTest):
             fake_handler.GET
         )
 
-        web.ctx.env = {"HTTP_ACCEPT": "application/json"}
-
-        with patch("nailgun.api.v1.handlers.base.content_json") as cj:
-            fake_handler.GET()
-            self.assertEqual(cj.call_count, 1)
-
         web.ctx.env = {"HTTP_ACCEPT": "*/*"}
-
-        with patch("nailgun.api.v1.handlers.base.content_json") as cj:
-            fake_handler.GET()
-            self.assertEqual(cj.call_count, 1)
-
         web.ctx.headers = []
         fake_handler.GET()
         self.assertIn(
@@ -136,7 +124,7 @@ class TestHandlers(BaseIntegrationTest):
         )
 
         web.ctx.headers = []
-        web.ctx.env = {"HTTP_ACCEPT": "text/plain"}
+        web.ctx.env = {"HTTP_ACCEPT": "application/json"}
         fake_handler.POST()
         self.assertIn(
             # we don't have plain/text serializer right now
@@ -144,6 +132,20 @@ class TestHandlers(BaseIntegrationTest):
             web.ctx.headers
         )
 
+    def test_invalid_handler_output(self):
+
+        class FakeHandler(object):
+
+            @handle_errors
+            @serialize
+            def GET(self):
+                return {set([1, 2, 3])}
+
+        fake_handler = FakeHandler()
+        web.ctx.env = {"HTTP_ACCEPT": "*/*"}
+        web.ctx.headers = []
+        self.assertRaises(web.HTTPError, fake_handler.GET)
+
     def test_get_param_as_set(self):
         urls = ("/hello", "hello")
 
@@ -160,3 +162,26 @@ class TestHandlers(BaseIntegrationTest):
 
         self.assertEqual(set(json.loads(resp.data)),
                          set(['1', '4', '777', 'x']))
+
+    def check_get_requested_mime(self, headers, expected_mime):
+        urls = ("/hello", "hello")
+
+        class hello(object):
+            def GET(self_inner):
+                web.header('Content-Type', 'text/plain')
+                return BaseHandler.get_requested_mime()
+
+        app = web.application(urls, {'hello': hello})
+        resp = app.request('/hello', headers=headers)
+
+        self.assertEqual(resp.data, expected_mime)
+
+    def test_get_requested_mime1(self):
+        self.check_get_requested_mime({'ACCEPT': 'text/html'}, 'text/html')
+
+    def test_get_requested_mime2(self):
+        self.check_get_requested_mime(
+            {'ACCEPT': 'text/plain;q=0.7, text/html;level=1,'}, 'text/plain')
+
+    def test_get_requested_default(self):
+        self.check_get_requested_mime({}, 'application/json')