refactor backend module architecture

app/foundation/dom.py

@@ -0,0 +1,34 @@
+from typing import Union
+
+
+class DomUtils:
+    """提供 XML DOM 节点读取和创建辅助能力。"""
+
+    @staticmethod
+    def tag_value(tag_item, tag_name: str, attname: str = "", default: Union[str, int] = None):
+        """
+        解析XML标签值
+        """
+        tagNames = tag_item.getElementsByTagName(tag_name)
+        if tagNames:
+            if attname:
+                attvalue = tagNames[0].getAttribute(attname)
+                if attvalue:
+                    return attvalue
+            else:
+                firstChild = tagNames[0].firstChild
+                if firstChild:
+                    return firstChild.data
+        return default
+
+    @staticmethod
+    def add_node(doc, parent, name: str, value: str = None):
+        """
+        添加一个DOM节点
+        """
+        node = doc.createElement(name)
+        parent.appendChild(node)
+        if value is not None:
+            text = doc.createTextNode(str(value))
+            node.appendChild(text)
+        return node