Common REST data handling

Adding common REST data handling
to monasca-common project

Change-Id: I982d0afbc51863905c56e1d4c24307fea261d944

monasca_common/rest/exceptions.py

@@ -0,0 +1,39 @@
+# Copyright 2015 FUJITSU LIMITED
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+
+class UnsupportedContentTypeException(Exception):
+    """Exception thrown if content type is not supported."""
+    pass
+
+
+class UnreadableContentError(IOError):
+    """Exception thrown if reading data fails
+
+    :py:class`.UnreadableContentError` may be thrown
+    if data was impossible to read from input
+
+    """
+    pass
+
+
+class DataConversionException(Exception):
+    """Exception thrown if data transformation fails
+
+    :py:class`.DataConversionException` may be thrown
+    if data was impossible to transform into target
+    representation according to content_type classifier.
+
+    """
+    pass

monasca_common/rest/utils.py

@@ -0,0 +1,116 @@
+# Copyright 2015 FUJITSU LIMITED
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import ujson as json
+
+import six
+
+from monasca_common.rest import exceptions
+
+ENCODING = 'utf8'
+
+TEXT_CONTENT_TYPE = 'text/plain'
+JSON_CONTENT_TYPE = 'application/json'
+
+
+def _try_catch(fun):
+
+    @six.wraps(fun)
+    def wrapper(*args, **kwargs):
+        try:
+            return fun(*args, **kwargs)
+        except Exception as ex:
+            raise exceptions.DataConversionException(str(ex))
+
+    return wrapper
+
+
+@_try_catch
+def as_json(data, **kwargs):
+    """Writes data as json.
+
+    :param dict data: data to convert to json
+    :param kwargs kwargs: kwargs for json dumps
+    :return: json string
+    :rtype: str
+    """
+
+    if 'sort_keys' not in kwargs:
+        kwargs['sort_keys'] = False
+    if 'ensure_ascii' not in kwargs:
+        kwargs['ensure_ascii'] = False
+
+    data = json.dumps(data, **kwargs)
+
+    return data.encode(ENCODING)
+
+
+@_try_catch
+def from_json(data, **kwargs):
+    """Reads data from json str.
+
+    :param str data: data to read
+    :param kwargs kwargs: kwargs for json loads
+    :return: read data
+    :rtype: dict
+    """
+    return json.loads(data, **kwargs)
+
+
+_READABLE_CONTENT_TYPES = {
+    TEXT_CONTENT_TYPE: lambda content: content,
+    JSON_CONTENT_TYPE: from_json
+}
+
+
+def read_body(payload, content_type=JSON_CONTENT_TYPE):
+    """Reads HTTP payload according to given content_type.
+
+    Function is capable of reading from payload stream.
+    Read data is then processed according to content_type.
+
+    Note:
+        Content-Type is validated. It means that if read_body
+        body is not capable of reading data in requested type,
+        it will throw an exception.
+
+    If read data was empty method will return false boolean
+    value to indicate that.
+
+    Note:
+        There is no transformation if content type is equal to
+        'text/plain'. What has been read is returned.
+
+    :param stream payload: payload to read, payload should have read method
+    :param str content_type: payload content type, default to application/json
+    :return: read data, returned type depends on content_type or False
+             if empty
+
+    :exception: :py:class:`.UnreadableBody` - in case of any failure when
+                                              reading data
+
+    """
+    if content_type not in _READABLE_CONTENT_TYPES:
+        msg = ('Cannot read %s, not in %s' %
+               (content_type, _READABLE_CONTENT_TYPES))
+        raise exceptions.UnsupportedContentTypeException(msg)
+
+    try:
+        content = payload.read()
+        if not content:
+            return None
+    except Exception as ex:
+        raise exceptions.UnreadableContentError(str(ex))
+
+    return _READABLE_CONTENT_TYPES[content_type](content)

requirements.txt

@@ -5,3 +5,4 @@ kafka-python>=0.9.1,<0.9.3
 PyMySQL>=0.6.7
 oslo.config<2.5.0
 pbr>=0.11,<2.0
+ujson>=1.34