如何在java中更新xml文件

Question

我有一个xml文件调用data.xml,如下面的代码.项目可以从客户端运行没问题,它可以读取xml文件.我现在遇到的问题是我想编写一个可以更新startdate和enddate的函数.我不知道如何开始.帮助将不胜感激.

  <?xml version="1.0" encoding="UTF-8" standalone="no"?>
<data>
       <username>admin</username>
       <password>12345</password>
       <interval>1</interval>
       <timeout>90</timeout>
       <startdate>01/01/2013</startdate>
       <enddate>06/01/2013</enddate>
       <ttime>1110</ttime>
    </data>

我的main.java

    public class main
    {
     public static void main(String[] args) 
      {
          Calendar cal2 =null;

    try {   

              //read the xml      
              File data = new File("data.xml");  
              DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();         
              DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();           
              Document doc = dBuilder.parse(data);         
              doc.getDocumentElement().normalize();

     for (int i = 0; i < nodes.getLength(); i++) {     
              Node node = nodes.item(i);           
                if (node.getNodeType() == Node.ELEMENT_NODE) {     
                    Element element = (Element) node;   
                    username = getValue("username", element);
                    startdate = getValue("startdate", element);
                    enddate = getValue("enddate", element);
                  }
       }


  date = startdate; 
  Date date_int = new SimpleDateFormat("MM/dd/yyyy", Locale.ENGLISH).parse(date); 
  cal2 = Calendar.getInstance(); 
 cal2.setTime(date_int); 


     //loop the child node to update the initial date
              for (int i = 0; i < nodes.getLength(); i++) {    
                  Node node = nodes.item(i);           
                    if (node.getNodeType() == Node.ELEMENT_NODE) {     
                        Element element = (Element) node;

                        setValue("startdate", element , date_int.toString());
                  }
              }

            //write the content in xml file
                TransformerFactory transformerFactory = TransformerFactory.newInstance();
                Transformer transformer = transformerFactory.newTransformer();
                DOMSource source = new DOMSource(doc);
                StreamResult result = new StreamResult(new File("data.xml"));
                transformer.transform(source, result);

        } catch (Exception ex) {    
          log.error(ex.getMessage());       
          ex.printStackTrace();       
        }
    }


      private static void setValue(String tag, Element element , String input) {  
            NodeList nodes = element.getElementsByTagName(tag).item(0).getChildNodes();   
            Node node = (Node) nodes.item(0); 
            node.setTextContent(input);

    }

Answer 1

首先,您的XML中存在错误,您有额外的<data>标记.我删除了它.现在您有两种选择可以使用SAX或DOM.我建议DOM理由是你可以使用XML读取完整的XML DOM,对于这样的一小段XML,它是更好的选择.

码

import java.io.File;
import java.io.IOException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.xml.sax.SAXException;

public class ModifyXMLFile {

    public static void main(String argv[]) {

        try {
            String filepath = "file.xml";
            DocumentBuilderFactory docFactory = DocumentBuilderFactory
                    .newInstance();
            DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
            Document doc = docBuilder.parse(filepath);

            // Get the root element
            Node data= doc.getFirstChild();

            Node startdate = doc.getElementsByTagName("startdate").item(0);

            // I am not doing any thing with it just for showing you
            String currentStartdate = startdate.getNodeValue();

            DateFormat df = new SimpleDateFormat("dd/MM/yyyy");
            Date today = Calendar.getInstance().getTime();

            startdate.setTextContent(df.format(today));

            // write the content into xml file
            TransformerFactory transformerFactory = TransformerFactory
                    .newInstance();
            Transformer transformer = transformerFactory.newTransformer();
            DOMSource source = new DOMSource(doc);
            StreamResult result = new StreamResult(new File(filepath));
            transformer.transform(source, result);

            System.out.println("Done");

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

更正了XML

<?xml version="1.0" encoding="UTF-8"?>
<data>
   <username>admin</username>
   <password>12345</password>
   <interval>1</interval>
   <timeout>90</timeout>
   <startdate>29/07/2015</startdate>
   <enddate>06/01/2013</enddate>
   <ttime>1110</ttime>
</data>

Answer 2

首先加载XML文件...

DocumentBuilderFactory f = DocumentBuilderFactory.newInstance();
DocumentBuilder b = f.newDocumentBuilder();
Document doc = b.parse(new File("Data.xml"));

现在，有几种方法可以执行此操作，但简单来说，您可以使用xpath API查找所需的节点并更新其内容

XPath xPath = XPathFactory.newInstance().newXPath();
Node startDateNode = (Node) xPath.compile("/data/startdate").evaluate(doc, XPathConstants.NODE);
startDateNode.setTextContent("29/07/2015");

xPath = XPathFactory.newInstance().newXPath();
Node endDateNode = (Node) xPath.compile("/data/enddate").evaluate(doc, XPathConstants.NODE);
endDateNode.setTextContent("29/07/2015");

然后保存Document回文件...

Transformer tf = TransformerFactory.newInstance().newTransformer();
tf.setOutputProperty(OutputKeys.INDENT, "yes");
tf.setOutputProperty(OutputKeys.METHOD, "xml");
tf.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");

DOMSource domSource = new DOMSource(doc);
StreamResult sr = new StreamResult(new File("Data.xml"));
tf.transform(domSource, sr);