Merge trunk

nova/wsgi.py

@@ -21,7 +21,6 @@
 Utility methods for working with WSGI servers
 """
 
-import json
 import os
 import sys
 from xml.dom import minidom
@@ -39,6 +38,7 @@ from paste import deploy
 
 from nova import flags
 from nova import log as logging
+from nova import utils
 
 
 FLAGS = flags.FLAGS
@@ -147,8 +147,9 @@ class Application(object):
 
 
 class Middleware(Application):
-    """
-    Base WSGI middleware wrapper. These classes require an application to be
+    """Base WSGI middleware.
+
+    These classes require an application to be
     initialized that will be called next.  By default the middleware will
     simply call its wrapped app, or you can override __call__ to customize its
     behavior.
@@ -181,13 +182,30 @@ class Middleware(Application):
             return cls(app, **local_config)
         return _factory
 
-    def __init__(self, application):  # pylint: disable-msg=W0231
+    def __init__(self, application):
         self.application = application
 
+    def process_request(self, req):
+        """Called on each request.
+
+        If this returns None, the next application down the stack will be
+        executed. If it returns a response then that response will be returned
+        and execution will stop here.
+
+        """
+        return None
+
+    def process_response(self, response):
+        """Do whatever you'd like to the response."""
+        return response
+
     @webob.dec.wsgify
-    def __call__(self, req):  # pylint: disable-msg=W0221
-        """Override to implement middleware behavior."""
-        return self.application
+    def __call__(self, req):
+        response = self.process_request(req)
+        if response:
+            return response
+        response = req.get_response(self.application)
+        return self.process_response(response)
 
 
 class Debug(Middleware):
@@ -373,7 +391,7 @@ class Serializer(object):
         try:
             is_xml = (datastring[0] == '<')
             if not is_xml:
-                return json.loads(datastring)
+                return utils.loads(datastring)
             return self._from_xml(datastring)
         except:
             return None
@@ -406,7 +424,7 @@ class Serializer(object):
             return result
 
     def _to_json(self, data):
-        return json.dumps(data)
+        return utils.dumps(data)
 
     def _to_xml(self, data):
         metadata = self.metadata.get('application/xml', {})