记一次项目中协议解析代码重构
现在项目里的协议解析很混乱，而且不能复用父类的解析代码，新人扩展协议很麻烦，尤其会把代码写的很丑陋，比如下面这样：
要解析的协议格式：
<SyncUploadRequestUnit>
<Parameter name="ContentName" value="L1NhbXBsZS9iYWNrdXAudGFyLmd6LjA="/>
<Parameter name="DataType" value="U2FtcGxl"/>
<Parameter name="PublishDate" value="2013-12-04"/>
<Parameter name="EffectiveDate" value="2013-12-04"/>
<Parameter name="EffectiveTime" value="07:47:00"/>
<Parameter name="FileName" value="L1NhbXBsZS9iYWNrdXAudGFyLmd6"/>
<Parameter name="UnassignFlag" value="N"/>
<Parameter name="CRCValue" value="766D29E5"/>
<Parameter name="AssignmentId" value=""/>
<Parameter name="Title" value="YmFja3Vw"/>
<Parameter name="Keywords" value=""/>
<Parameter name="Version" value=""/>
<EfbList>
<Parameter name="EfbName" value="EFB-1"/>
<Parameter name="EfbName" value="EFB-2"/>
</EfbList>
<DepList>
<Content>
<Parameter name="DataType" value="U2FtcGxl "/>
<Parameter name="FileName" value="dGVzdDIudHh0 "/>
<Parameter name="Revision" value="MjIy "/>
</Content>
<Content>
<Parameter name="DataType" value="L1NhbXBsZS9iYWNrdXAudGFyLmd6LjA="/>
<Parameter name="FileName" value="dGVzdDIudHh0 "/>
<Parameter name="Revision" value="MjIy "/>
</Content>
</DepList>
</SyncUploadRequestUnit>
解析代码，每个子类都得实现自己的：
def parse(data, encoded=True):
syncUnitDOM = parseXmlString(data)
syncUnitNode = syncUnitDOM.childNodes[0]
paramMap = {}
efbList = []
depList = []
for syncUnitChildNode in syncUnitNode.childNodes:
if syncUnitChildNode.nodeName == PARAMETER_TAG:
name = str(syncUnitChildNode.getAttribute(NAME_TAG))
value = str(syncUnitChildNode.getAttribute(VALUE_TAG))
paramMap[name] = value
elif syncUnitChildNode.nodeName == EFBLIST_TAG:
efbListParameterList = syncUnitChildNode.getElementsByTagName(PARAMETER_TAG)
for efbListNode in efbListParameterList:
if str(efbListNode.getAttribute(NAME_TAG)) == EFB_NAME:
efbList.append(str(efbListNode.getAttribute(VALUE_TAG)))
elif syncUnitChildNode.nodeName == DEPLIST_TAG:
for contentNode in syncUnitChildNode.childNodes:
if contentNode.nodeName == CONTENT_TAG:
content = {}
for conParamNode in contentNode.getElementsByTagName(PARAMETER_TAG):
paramName = str(conParamNode.getAttribute(NAME_TAG))
if paramName in ENCODED_TAGS and encoded:
content[paramName] = decode(str(conParamNode.getAttribute(VALUE_TAG)))
else:
content[paramName] = str(conParamNode.getAttribute(VALUE_TAG))
depList.append(content)
不管别人舒不舒服，我受不了了。这种情况必须得改善，一开始想到的是go 语言解析xml那种方式，后来又觉得像声明orm model那样更方便，看了peewee这个orm框架后就开工了，下面是一个model的描述：
class SyncUploadRequestUnit(Model):
content_name = ParameterField('ContentName')
data_type = ParameterField('DataType')
publish_date = ParameterField('PublishDate')
effective_time = ParameterField('EffectiveTime')
effective_date = ParameterField('EffectiveDate')
filename = ParameterField('FileName')
unassign_flag = ParameterField('UnassignFlag')
crc_value = ParameterField('CRCValue')
assignment_id = ParameterField('AssignmentId')
title = ParameterField('Title')
keywords = ParameterField('Keywords')
version = ParameterField('Version')
efb_list = StringListField('EfbList', 'EfbName')
dep_list = ModelListField('DepList', Content)
看着很直观是不是，下面是其基类
import base64
import xml.etree.ElementTree as ET
BEGIN_TAG = 'CM'
PARAMETER_TAG = 'Parameter'
ENCODED_TAGS = ['DataType', 'FileName', 'ContentName', 'Revision', 'Title']
def encode(value):
return base64.encodestring(value.encode('utf-8'))
def decode(value):
return base64.decodestring(value).decode('utf-8')
class FieldDescriptor(object):
def __init__(self, name, field):
self.name = name
self.field = field
def __get__(self, instance, cls):
value = instance._data.get(self.field.tag, None)
return value
def __set__(self, instance, value):
instance._data[self.field.tag] = value
class TagField(object):
def __init__(self, tag):
self.tag = tag\
def parse(self, root, setter, encoded=False):
for element in root.iterfind(self.tag):
setter(self.tag, element.text, encoded)
def transfer_to_xml(self, parent, getter, encoded=False):
element = ET.SubElement(parent, self.tag)
element.text = getter(self.tag, encoded) or ''
class ParameterField(object):
def __init__(self, name):
self.tag = name
def parse(self, root, setter, encoded=False):
for element in root.iterfind(PARAMETER_TAG):
setter(element.get('name'), element.get('value'), encoded)
def transfer_to_xml(self, parent, getter, encoded=False):
attrs = {
'name': self.tag,
'value': getter(self.tag, encoded)
}
ET.SubElement(parent, PARAMETER_TAG, attrs)
class StringListField(object):
def __init__(self, container_name, element_name):
self.tag = container_name
self.element_name = element_name
def parse(self, root, setter, encoded=False):
children = []
setter(self.tag, children)
container = root.find(self.tag)
if container is None:
return
for element in container.iterfind(PARAMETER_TAG):
children.append(element.get('value'))
def transfer_to_xml(self, parent, getter, encoded=False):
value_list = getter(self.tag, encoded)
if value_list is None or len(value_list) == 0:
return
parent = ET.SubElement(parent, self.tag)
for value in value_list:
attrs = {
'name': self.element_name,
'value': value
}
ET.SubElement(parent, PARAMETER_TAG, attrs)
class ModelListField(object):
def __init__(self, container_name, model):
self.tag = container_name
self.model = model
self.model_tag = model.__name__
def parse(self, root, setter, encoded=False):
children = []
setter(self.tag, children)
container = root.find(self.tag)
if container is None:
return
for element in container.iterfind(self.model_tag):
child = self.model()
child.parse_element(element, encoded)
children.append(child)
def transfer_to_xml(self, parent, getter, encoded=False):
value_list = getter(self.tag, encoded)
if value_list is None or len(value_list) == 0:
return
parent = ET.SubElement(parent, self.tag)
for value in value_list:
value.as_xml(parent, encoded)
class ModelField(object):
def __init__(self, model):
self.model = model
self.tag = model.__name__
def parse(self, root, setter, encoded=False):
element = root.find(self.tag)
if element is not None:
child = self.model()
child.parse_element(element, encoded)
setter(self.tag, child)
def transfer_to_xml(self, parent, getter, encoded=False):
value = getter(self.tag, encoded)
if value is not None:
value.as_xml(parent, encoded)
FIELD_LIST = [TagField, ParameterField, StringListField, ModelField, ModelListField]
class BaseModel(type):
def __new__(cls, name, bases, attrs):
if not bases:
return super(BaseModel, cls).__new__(cls, name, bases, attrs)
fields = {
TagField: [],
ParameterField: [],
ModelField: [],
StringListField: [],
ModelListField: [],
}
for attr, field in attrs.items():
field_class = type(field)
if field_class in fields:
fields[field_class].append(field)
attrs[attr] = FieldDescriptor(attr, field)
attrs['_fields'] = fields
return super(BaseModel, cls).__new__(cls, name, bases, attrs)
class Model(object):
__metaclass__ = BaseModel
def __init__(self, data=None):
self._data = data or {}
def parse(self, data, encoded=False):
return self.parsestring(data, encoded)
def parsestring(self, data, encoded=False):
root = ET.fromstring(data)
return self.parse_element(root, encoded)
def parse_element(self, root, encoded=False):
for field_list in self._fields.values():
for field in field_list:
field.parse(root, self.__set, encoded)
return self
def as_xml(self, parent=None, encoded=False):
tag = self.__class__.__name__
if parent is not None:
parent = ET.SubElement(parent, tag)
else:
parent = ET.Element(BEGIN_TAG)
for field_class in FIELD_LIST:
for field in self._fields.get(field_class, []):
field.transfer_to_xml(parent, self.__get, encoded)
return parent
def as_pretty_xml(self, encoded=False):
tree = self.as_xml(encoded=encoded)
self.indent(tree)
return ET.tostring(tree)
def indent(self, elem, level=0):
i = "\n" + level * " "
if len(elem):
if not elem.text or not elem.text.strip():
elem.text = i + " "
if not elem.tail or not elem.tail.strip():
elem.tail = i
for elem in elem:
self.indent(elem, level+1)
if not elem.tail or not elem.tail.strip():
elem.tail = i
else:
if level and (not elem.tail or not elem.tail.strip()):
elem.tail = i
def __set(self, name, value, encoded=False):
if encoded and name in ENCODED_TAGS:
value = decode(value)
self._data[name] = value
def __get(self, name, encoded=False):
value = self._data.get(name, None)
if encoded and value and name in ENCODED_TAGS:
value = encoded(value)
return value