如何使用 DOM 追加现有 XML 文件而不覆盖现有数据?在java中 [英] How to append an existing XML file using DOM without overwriting the existing data? in java

问题描述

我对如何将 xml 数据附加到已经存在的数据感到非常困惑，请给我您的建议，我的代码是这样的

i have a very confused about the how the xml data can be append to already existed data give me your suggestions my code is like this

 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

我也可以轻松解析和更新，但我不明白如何附加以前的数据，请帮助我

and i can do easily parse and update also but i can't understand how i can append previous data please help me

推荐答案

很简单.假设您想将新的 Employees 附加到您的 XML 中.无需创建新根，您只需使用 getElementsByName() 之类的

It's pretty easy. Say, you want to append new Employees to your XML. Instead of creating a new root you'd simply find it using getElementsByName() like

// 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

还有一个 Document.getElementById() 方法，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，首先使用 XPath 查找节点，然后像往常一样使用 append().

There's a Document.getElementById() method as well that you could use if an element has been assigned an identifier. To insert something deep down the tree use XPath to find the node first then append() as usual.

(添加示例代码)
您不能有两个根节点，即两个 <Employees> 标记作为根.那是无效的 XML.您需要的是一个根 <Employees> 标记内的多个 <Employee> 标记.此外，坚持骆驼或大写.我使用大写字母来保持一致性.

EDIT : (Sample code added)
You can't have two root nodes i.e. two <Employees> tags as root. That's invalid XML. What you need is multiple <Employee> tags inside one single root <Employees> tag. Also, stick to either camel or capital case. I'm using capitals for consistency.

// 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;
}

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