这是代码：
public Document getFile(String path) throws ParserConfigurationException, SAXException, IOException{
         String classpath = FileInputUtil.class.getClassLoader().getResource("").getPath();
         String parentpath = classpath.substring(0,classpath.lastIndexOf("classes"))+"date/";
         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
         DocumentBuilder db = dbf.newDocumentBuilder();
         Document doc = db.parse(parentpath+path);
         return doc;
     }
     public static void main(String[] args) throws Exception{
         FileInputUtil fiu = new FileInputUtil();
         Document doc = fiu.getFile("aboutUs.xml");
         System.out.println(doc);
     }
这是结果：
[#document: null]
请问一下怎么会是null，我打印过db.parse(parentpath+path)，也是null，该文件的确存在，里面也有内容