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。该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开始日期和结束日期的函数。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);

    }

原文由 Big Ticket 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

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，有几种方法可以做到这一点，但简单地说，您可以使用 xpath API 找到您想要的节点并更新它们的内容

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");

然后将 Document 保存回文件…

 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);

原文由 MadProgrammer 发布，翻译遵循 CC BY-SA 3.0 许可协议

Answer 2

首先，您的 XML 中存在错误，您有额外的 <data> 标记。我已经删除了它。现在您有两个选项可以使用 SAX 或 DOM 。我建议 DOM 原因是您可以使用 DOM 读取完整的 XML，对于像这样的一小段 XML，这是更好的选择。

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>

原文由 Shahzeb 发布，翻译遵循 CC BY-SA 3.0 许可协议