How to append an existing XML file using DOM without overwriting the existing data? in java

问题

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

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

回答1:

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

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.

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;
}

来源：https://stackoverflow.com/questions/17249758/how-to-append-an-existing-xml-file-using-dom-without-overwriting-the-existing-da

标签

java

xml

dom

append