我有一个简单的XML文件
<requirements>
<requirement>
<name> SwitchON</name>
<id>1</id>
<text>The Light shall turn on when the Switch is on.</text>
</requirement>
<requirement>
<name>SwitchOFF</name>
<id>2</id>
<text>The Light shall turn off when the Switch is off.</text>
</requirement>
<requirement>
<name>Lightbulb</name>
<id>3</id>
<text>The Light bulb shall be connected </text>
</requirement>
<requirement>
<name>Power</name>
<id>4</id>
<text>The Light shall have the power supply</text>
</requirement>
</requirements>
我试图在表格模型中显示此文件中的信息。 我有一个方法(readFromXMl),它读取XML文件并返回一个表模型。
public static RequirementTable readFromXMl(String fileName) {
RequirementTable T = new RequirementTable();
Requirement R = new Requirement();
try {
DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = docBuilderFactory.newDocumentBuilder();
Document doc = docBuilder.parse(new File(fileName));
doc.getDocumentElement().normalize();
NodeList listOfRequirements = doc.getElementsByTagName("requirement");
int test = listOfRequirements.getLength();
System.out.println("Total no of people : " + test);
for (int i = 0; i < listOfRequirements.getLength(); i++) {
Node RequirementNode = listOfRequirements.item(i);
if (RequirementNode.getNodeType() == Node.ELEMENT_NODE) {
Element RequirementElement = (Element) RequirementNode;
NodeList IdList = RequirementElement.getElementsByTagName("id");
Element IdElement = (Element) IdList.item(0);
NodeList textIdList = IdElement.getChildNodes();
R.setId(Integer.parseInt(textIdList.item(0).getNodeValue()));
NodeList DescriptionList = RequirementElement.getElementsByTagName("text");
Element DescriptionElement = (Element) DescriptionList.item(0);
NodeList textDescriptionList = DescriptionElement.getChildNodes();
R.setText(textDescriptionList.item(0).toString());
NodeList NameList = RequirementElement.getElementsByTagName("name");
Element NameElement = (Element) NameList;
NodeList textNameList = NameElement.getChildNodes();
if (textNameList.item(0).toString().equals("SwitchON")) {
T.addRequirement((SwitchOnReq)R);
} else if (textNameList.item(0).toString().equals("SwitchOFF")) {
T.addRequirement((SwitchOFFReq)R);
} else if (textNameList.item(0).toString().equals("LightBulb")) {
T.addRequirement((BulbRequirement)R);
} else if (textNameList.item(0).toString().equals("Power")) {
T.addRequirement((PowerRequirement)R);
}
}
}
} catch (SAXParseException err) {
System.out.println("** Parsing error" + ", line " + err.getLineNumber() + ", uri " + err.getSystemId());
System.out.println(" " + err.getMessage());
} catch (SAXException e) {
Exception x = e.getException();
((x == null) ? e : x).printStackTrace();
} catch (Throwable t) {
t.printStackTrace();
}
return T;
}
但是在这一行中,我收到一个错误,指出指针为空
Element IdElement = (Element) IdList.item(0);
IdElement为空!!
答案 0 :(得分:1)
而不是所有的循环和其他xml丑陋,让我建议一个小帮手方法:
private static String getNodeValue(Node n, String path)
throws XPathExpressionException {
XPath xpath = XPathFactory.newInstance().newXPath();
return (String) xpath.evaluate(path, n, XPathConstants.STRING);
}
像这样使用:
for (int i = 0; i < listOfRequirements.getLength(); i++) {
Node RequirementNode = listOfRequirements.item(i);
System.out.println("name:" + getNodeValue(RequirementNode, "name"));
System.out.println("id:" + getNodeValue(RequirementNode, "id"));
System.out.println("text:" + getNodeValue(RequirementNode, "text"));
...
获取所有值并设置您的要求。