java - 如何在不覆盖现有数据的情况下使用 DOM append 现有 XML 文件？在 java

Question

我对如何将 xml 数据 append 到已存在的数据感到非常困惑，给我你的建议我的代码是这样的

 Document doc = DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();//db.newDocument();//create document

        Element root = doc.createElement("Employees");//cretae Elements
        doc.appendChild(root);

        Comment cmt = doc.createComment("Employee Details");//Add comment to xml
        root.appendChild(cmt);

        Element employee = doc.createElement("employee");//create Element
        //employee.appendChild(doc.)
        root.appendChild(employee);

        Attr genderAttr = doc.createAttribute("Gender");
        System.out.print("Enter your gender :");
        String gend = br.readLine();
        genderAttr.setValue(gend);
        employee.setAttributeNode(genderAttr);

        System.out.print("Enter first name:");
        String child = br.readLine();
        Element FName = doc.createElement("firstName");
        FName.appendChild(doc.createTextNode(child));//set xml text
        employee.appendChild(FName);

        System.out.print("Enter last name:");
        String child1 = br.readLine();
        Element LName = doc.createElement("lastName");            
        LName.appendChild(doc.createTextNode(child1));
        employee.appendChild(LName);

        //root.appendChild(employee);
        //doc.appendChild(root);

        //to write on file/screen
        TransformerFactory tf = TransformerFactory.newInstance();
        Transformer tr = tf.newTransformer();
        tr.setOutputProperty(OutputKeys.INDENT, "yes");
        DOMSource source = new DOMSource(doc);//source             
        //File shopOrder = new File("src"+File.separator+"xmlparsing"+File.separator+"xmlParse1.xml");//get the file
        StreamResult res = new StreamResult(new File("src"+File.separator+"xmlparsing"+File.separator+"xmlParse1.xml"));//Destination
        tr.transform(source, res);//to write on file

我也可以轻松地解析和更新，但我不明白如何 append 以前的数据请帮助我

Answer 1

这很容易。说，你想追加新的 Employees到您的 XML。您无需创建新根，只需使用 getElementsByName() 即可找到它喜欢

// find root
NodeList rootList = doc.getElementsByName("Employees");
Node root = rootList.item(0);

Element employee = doc.createElement("employee"); //create new Element
root.appendChild(employee); // append as before

有一个 Document.getElementById()如果已为元素分配了标识符，您也可以使用该方法。要在树的深处插入一些东西，请使用 XPath先找到节点然后append()和往常一样。

编辑:(添加示例代码)
你不能有两个根节点，即两个 <Employees>标记为根。那是无效的 XML。你需要的是多个<Employee>一个根内的标签 <Employees>标签。另外，坚持使用 Camel 或大写字母。我使用大写字母是为了保持一致性。

// find root
NodeList rootList = doc.getElementsByName("Employees");
Node root = rootList.item(0);

// append using a helper method
root.appendChild(createEmployee(doc, "male", "John", "Doe"));

public Element createEmployee(Document doc,
                              String gender, String fname, String lname) {
  // create new Employee
  Element employee = doc.createElement("Employee");
  employee.setAttribute("gender", gender);

  // create child nodes
  Element firstName = doc.createElement("FirstName");
  firstName.appendChild(doc.createTextNode(fname));

  Element lastName = doc.createElement("LastName");
  lastName.appendChild(doc.createTextNode(lname));

  // append and return
  employee.appendChild(firstName);
  employee.appendChild(lastName);

  return employee;
}