如何在xml java中更新节点值

我目前正在开发一个xml项目。 到目前为止，我已经使用Dom Parser成功将我的xml链接到我的java类。 我在下面提供了代码。 我正在努力的是将我的startdate的月份更新为1，所以像这样的2/1 / 2013,3 / 1/2013 …将相应地在xml文件中更改。 我在底部调用updateDate方法，但是当我调用它时，xml文件不会更新它的值。 帮助将不胜感激

data.xml 之前

    hello123 01/01/2011 06/01/2013  

渴望data.xml 之后

    hello123 02/01/2011 <--- This will change 06/01/2013  

main.java

  public class main { public static void main(String[] args) { Calendar cal2 = null; String username = null; String startdate = null; String enddate = null; String date = null; String date_end = null; try { 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 //end date Date date_end = new SimpleDateFormat("MM/dd/yyyy", Locale.ENGLISH).parse(enddate); Calendar end_date_cal = Calendar.getInstance(); end_date_cal.setTime(date_end); // initial date Date date_int = new SimpleDateFormat("MM/dd/yyyy", Locale.ENGLISH).parse(date); cal2 = Calendar.getInstance(); cal2.setTime(date_int); //call the method updateDate(cal2); 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); System.out.println("Update Successfully"); } } catch (Exception ex) { log.error(ex.getMessage()); ex.printStackTrace(); } } private static void updateDate(Calendar cal2){ cal2.add(Calendar.MONTH, 1); //need to push it back to the calendar } private static String getValue(String tag, Element element) { NodeList nodes = element.getElementsByTagName(tag).item(0).getChildNodes(); Node node = (Node) nodes.item(0); return node.getNodeValue(); } 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

Java 8的Time API

 DateTimeFormatter formatter = DateTimeFormatter.ofPattern("M/d/yyyy"); LocalDate ld = LocalDate.parse("2/1/2013", formatter); System.out.println("From " + formatter.format(ld)); ld = ld.plusMonths(1); System.out.println("To " + formatter.format(ld)); 

哪个打印

 From 2/1/2013 To 3/1/2013 

但是，您永远不会将该值应用回XML文档。 正如我在上一个问题中尝试演示的那样 ，您需要更改节点的textContent …

 node.setTextContent(formatter.format(ld)) 

这就是为什么我建议使用xPath而不是走文档内容

例如…

 import java.io.File; import java.io.IOException; import java.time.LocalDate; import java.time.format.DateTimeFormatter; import java.time.format.DateTimeParseException; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.ParserConfigurationException; import javax.xml.transform.OutputKeys; import javax.xml.transform.Transformer; import javax.xml.transform.TransformerException; import javax.xml.transform.TransformerFactory; import javax.xml.transform.TransformerFactoryConfigurationError; import javax.xml.transform.dom.DOMSource; import javax.xml.transform.stream.StreamResult; import javax.xml.xpath.XPath; import javax.xml.xpath.XPathConstants; import javax.xml.xpath.XPathExpressionException; import javax.xml.xpath.XPathFactory; import org.w3c.dom.DOMException; import org.w3c.dom.Document; import org.w3c.dom.Node; import org.xml.sax.SAXException; public class UpdateXML { public static void main(String[] args) { try { DocumentBuilderFactory f = DocumentBuilderFactory.newInstance(); DocumentBuilder b = f.newDocumentBuilder(); Document doc = b.parse(new File("Data.xml")); XPath xPath = XPathFactory.newInstance().newXPath(); Node startDateNode = (Node) xPath.compile("/data/startdate").evaluate(doc, XPathConstants.NODE); startDateNode.setTextContent(addMonthTo(startDateNode.getTextContent())); xPath = XPathFactory.newInstance().newXPath(); Node endDateNode = (Node) xPath.compile("/data/enddate").evaluate(doc, XPathConstants.NODE); endDateNode.setTextContent(addMonthTo(endDateNode.getTextContent())); 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("AData.xml")); tf.transform(domSource, sr); } catch (ParserConfigurationException | SAXException | IOException | XPathExpressionException | DOMException | TransformerFactoryConfigurationError | IllegalArgumentException | TransformerException exp) { exp.printStackTrace(); } } public static String addMonthTo(String value) { String patterns[] = {"M/d/yyyy", "M/dd/yyyy", "MM/d/yyyy", "MM/dd/yyyy"}; LocalDate ld = null; for (String pattern : patterns) { try { ld = LocalDate.parse(value, DateTimeFormatter.ofPattern(pattern)); break; } catch (DateTimeParseException exp) { } } if (ld == null) { throw new DateTimeParseException("Could not parse " + value + " with available patterns", value, -1); } ld = ld.plusMonths(1); return DateTimeFormatter.ofPattern("MM/dd/yyyy").format(ld); } } 

哪个…

   admin 12345 1 90 1/1/2013 06/01/2013 1110  

输出……

   admin 12345 1 90 02/01/2013 07/01/2013 1110  

我希望比起更早6个月的开始日期

Java 8

 String endDateValue = "07/01/2013"; DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MM/dd/yyyy"); LocalDate endDate = LocalDate.parse(endDateValue, formatter); LocalDate startDate = endDate.minusMonths(6); String startDateValue = formatter.format(startDate); 

日历

我更喜欢Joda-Time，但是

 String endDateValue = "07/01/2013"; SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy"); Date endDate = sdf.parse(endDateValue); Calendar cal = Calendar.getInstance(); cal.setTime(endDate); cal.add(Calendar.MONTH, -6); Date startDate = cal.getTime(); String startDateVaue = sdf.format(startDate);