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如何在xml java中更新节点值
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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,因此像这样的2/2 / 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
<?xml version="1.0" encoding="UTF-8">
<data>
<username>hello123</username>
<startdate>01/01/2011</startdate>
<enddate>06/01/2013</enddate>
</data>
渴望data.xml之后
<?xml version="1.0" encoding="UTF-8">
<data>
<username>hello123</username>
<startdate>02/01/2011</startdate> <--- This will change
<enddate>06/01/2013</enddate>
</data>
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);
}
}
解决方法:
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.当我试图在你的previous question中演示时,你需要更改节点的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…
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<data>
<username>admin</username>
<password>12345</password>
<interval>1</interval>
<timeout>90</timeout>
<startdate>1/1/2013</startdate>
<enddate>06/01/2013</enddate>
<ttime>1110</ttime>
</data>
并输出……
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<data>
<username>admin</username>
<password>12345</password>
<interval>1</interval>
<timeout>90</timeout>
<startdate>02/01/2013</startdate>
<enddate>07/01/2013</enddate>
<ttime>1110</ttime>
</data>
i want the startdate 6 months earlier then the enddate
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);
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