如何在java中更新xml文件 [英] How to update xml files in java

问题描述

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。我们将不胜感激。

I have a xml file call data.xml like the code below. The project can run from client side no problem and it can read the xml file. The problem I have now is I I want to write a function that can update the startdate and enddate. I have no idea how to get start. Help will be appreciated.

  <?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>

my main.java

my 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);

    }

推荐答案

首先出现您的XML中存在错误，您有额外的< data> 标记。我删除了它。现在您有两个选项可以使用 SAX 或 DOM 。我建议 DOM 原因是你可以使用 DOM 读取完整的XML，并且对于像这样的一小段XML来说更好的选择。

Firstly there is an error in your XML you have extra <data> tag . I have removed it. Now you have two options you could either use SAX or DOM. I would suggest DOM reason being that you can read full XML using DOM and for a small piece of XML like this it's better choice.

代码

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();
        }
    }
}

更正的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>

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