heat API : return response body as XML not JSON

AWS API returns response as XML, this implements a new response serializer which
turns dicts returned from the engine into AWS style XML responses.  Ref #125.
Updated following review comment.

Change-Id: I8170ed814be0b5cea98761a2723e12be216374a3
Signed-off-by: Steven Hardy <shardy@redhat.com>

bin/heat

@@ -91,7 +91,7 @@ def template_validate(options, arguments):
 
     client = get_client(options)
     result = client.validate_template(**parameters)
-    print json.dumps(result, indent=2)
+    print result
 
 
 @utils.catch_error('estimatetemplatecost')
@@ -188,7 +188,7 @@ def stack_create(options, arguments):
 
     c = get_client(options)
     result = c.create_stack(**parameters)
-    print json.dumps(result, indent=2)
+    print result
 
 
 @utils.catch_error('update')
@@ -234,7 +234,7 @@ def stack_update(options, arguments):
 
     c = get_client(options)
     result = c.update_stack(**parameters)
-    print json.dumps(result, indent=2)
+    print result
 
 
 @utils.catch_error('delete')
@@ -256,7 +256,7 @@ def stack_delete(options, arguments):
 
     c = get_client(options)
     result = c.delete_stack(**parameters)
-    print json.dumps(result, indent=2)
+    print result
 
 
 @utils.catch_error('describe')
@@ -276,7 +276,7 @@ def stack_describe(options, arguments):
 
     c = get_client(options)
     result = c.describe_stacks(**parameters)
-    print json.dumps(result, indent=2)
+    print result
 
 
 @utils.catch_error('event-list')
@@ -294,7 +294,7 @@ def stack_events_list(options, arguments):
 
     c = get_client(options)
     result = c.list_stack_events(**parameters)
-    print json.dumps(result, indent=2)
+    print result
 
 
 @utils.catch_error('list')
@@ -306,7 +306,7 @@ def stack_list(options, arguments):
     '''
     c = get_client(options)
     result = c.list_stacks()
-    print json.dumps(result, indent=2)
+    print result
 
 
 def get_client(options):

heat/api/v1/stacks.py

@@ -249,5 +249,5 @@ def create_resource(options):
     Stacks resource factory method.
     """
     deserializer = wsgi.JSONRequestDeserializer()
-    serializer = wsgi.JSONResponseSerializer()
+    serializer = wsgi.XMLResponseSerializer()
     return wsgi.Resource(StackController(options), deserializer, serializer)

heat/client.py

@@ -17,7 +17,7 @@
 Client classes for callers of a heat system
 """
 
-import json
+from lxml import etree
 import logging
 import os
 from heat.common import client as base_client
@@ -44,7 +44,8 @@ class V1Client(base_client.BaseClient):
         params['Action'] = action
 
         res = self.do_request(method, "/", params=params)
-        return json.loads(res.read())
+        doc = etree.fromstring(res.read())
+        return etree.tostring(doc, pretty_print=True)
 
     def list_stacks(self, **kwargs):
         return self.stack_request("ListStacks", "GET", **kwargs)

heat/common/wsgi.py

@@ -28,6 +28,9 @@ import os
 import signal
 import sys
 import time
+import re
+from lxml import etree
+
 
 import eventlet
 import eventlet.greenio
@@ -433,6 +436,34 @@ class JSONResponseSerializer(object):
         response.body = self.to_json(result)
 
 
+class XMLResponseSerializer(object):
+
+    def object_to_element(self, obj, element):
+        if isinstance(obj, list):
+            for item in obj:
+                subelement = etree.SubElement(element, "member")
+                self.object_to_element(item, subelement)
+        elif isinstance(obj, dict):
+            for key, value in obj.items():
+                subelement = etree.SubElement(element, key)
+                self.object_to_element(value, subelement)
+        else:
+            element.text = str(obj)
+
+    def to_xml(self, data):
+        # Assumption : root node is dict with single key
+        root = data.keys()[0]
+        eltree = etree.Element(root)
+        doc = etree.ElementTree(eltree)
+        self.object_to_element(data.get(root), eltree)
+        logging.debug("XML response : %s" % etree.tostring(eltree))
+        return etree.tostring(eltree)
+
+    def default(self, response, result):
+        response.content_type = 'application/xml'
+        response.body = self.to_xml(result)
+
+
 class Resource(object):
     """
     WSGI app that handles (de)serialization and controller dispatch.