如何使用StAX将元素添加到现有XML文件中？

Question

I have an XML file similar to the one below:

<?xml version="1.0" encoding="UTF-8"?>  
<a>  
<b id="1">xxx</b>
<b id="2">yyy</b>
<b id="3">zzz</b>
</a>  

Is there a way to add an element (eg. <b id="4">ddd</b> ) after <b id="3">zzz</b> with StAX parser? The approach I have thought of is to write the first part of the XML into a new file as below.

<?xml version="1.0" encoding="UTF-8"?>  
<a>  
<b id="1">xxx</b>
<b id="2">yyy</b>
<b id="3">zzz</b>

But I cannot figure out a solution to write exactly after the last element ( <b id="3">zzz</b> ). Do I need to open a new file for output again? Is it possible to do it using StAX?

Answer 1

An example of how you can do that on your own :

public static void addElementToXML(String value){

      DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
      DocumentBuilder db = null;
      Document doc = null;
      try {

        String filePath = "D:\\Loic_Workspace\\Test2\\res\\test.xml";
        db = dbf.newDocumentBuilder();
        doc = db.parse(new File(filePath));
        NodeList ndListe = doc.getElementsByTagName("b");

        Integer newId = Integer.parseInt(ndListe.item(ndListe.getLength()-1).getAttributes().item(0).getTextContent()) + 1;

        String newXMLLine ="<b id=\""+newId+"\">"+StringEscapeUtils.escapeXml(value)+"</b>";

        Node nodeToImport = db.parse(new InputSource(new StringReader(newXMLLine))).getElementsByTagName("b").item(0);

        ndListe.item(ndListe.getLength()-1).getParentNode().appendChild(doc.importNode(nodeToImport, true));

          TransformerFactory tFactory = TransformerFactory.newInstance();
          Transformer transformer = tFactory.newTransformer();
          transformer.setOutputProperty(OutputKeys.INDENT, "yes");  

          DOMSource source = new DOMSource(doc);
          StreamResult result = new StreamResult(new StringWriter());

         transformer.transform(source, result);


          Writer output = new BufferedWriter(new FileWriter(filePath));
          String xmlOutput = result.getWriter().toString();  
          output.write(xmlOutput);
          output.close();


      } catch (ParserConfigurationException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (SAXException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (TransformerConfigurationException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (TransformerException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }




}

Notice, that I've used StringEscapeUtils method from Commons Lang .

XMLManager.addElementToXML("& dqsd apzeze /<>'");

File before :

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<a>  
<b id="1">xxx</b>
<b id="2">yyy</b>
<b id="3">zzz</b>
</a>

File after :

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<a>  
<b id="1">xxx</b>
<b id="2">yyy</b>
<b id="3">zzz</b>
<b id="4">&amp; dqsd apzeze /&lt;&gt;'</b>
</a>

Answer 2

Yes, you need a temp file to write to. Here is an example how to do this with StAX:

Path in = Paths.get("file.xml");
Path temp = Files.createTempFile(null, null);
XMLEventFactory eventFactory = XMLEventFactory.newInstance();
try (FileWriter out = new FileWriter(temp.toFile())) {
    XMLEventReader reader = XMLInputFactory.newInstance().createXMLEventReader(new FileReader(in.toFile()));
    XMLEventWriter writer = XMLOutputFactory.newInstance().createXMLEventWriter(out);
    int depth = 0;
    while (reader.hasNext()) {
        XMLEvent event = reader.nextEvent();
        int eventType = event.getEventType();
        if (eventType == XMLStreamConstants.START_ELEMENT) {
            depth++;
        } else if (eventType == XMLStreamConstants.END_ELEMENT) {
            depth--;
            if (depth == 0) {
                List<Attribute> attrs = new ArrayList<>(1);
                attrs.add(eventFactory.createAttribute("id", "4"));
                writer.add(eventFactory.createStartElement("", null, "b", attrs.iterator(), null));
                writer.add(eventFactory.createCharacters("ddd"));
                writer.add(eventFactory.createEndElement("", null, "b"));
                writer.add(eventFactory.createSpace(System.getProperty("line.separator")));
            }
        }
        writer.add(event);
    }
    writer.flush();
    writer.close();
} catch (XMLStreamException | FactoryConfigurationError e) {
    throw new IOException(e);
}
Files.move(temp, in, StandardCopyOption.REPLACE_EXISTING);