如何获取具有特定属性值的特定XML元素?
问题描述:
我想通过采取参数type_id =“4218”的所有“<Type>
”元素从URL解析XML文件?如何获取具有特定属性值的特定XML元素?
XML文档:
<BSQCUBS Version="0.04" Date="Fri Dec 9 11:43:29 GMT 2011" MachineDate="Fri, 09 Dec 2011 11:43:29 +0000">
<Class class_id="385">
<Title>Football Matches</Title>
<Type type_id="4264" type_minbet="0.1" type_maxbet="2000.0">
...
</Type>
<Type type_id="5873" type_minbet="0" type_maxbet="0">
...
</Type>
<Type type_id="4725" type_minbet="0.1" type_maxbet="2000.0">
...
</Type>
<Type type_id="4218" type_minbet="0.1" type_maxbet="2000.0">
...
</Type>
<Type type_id="4221" type_minbet="0.1" type_maxbet="2000.0">
...
</Type>
<Type type_id="4218" type_minbet="0.1" type_maxbet="2000.0">
...
</Type>
<Type type_id="4299" type_minbet="0.1" type_maxbet="2000.0">
...
</Type>
</Class>
</BSQCUBS>
这里是我的Java代码:
DocumentBuilder db = dbf.newDocumentBuilder();
Document doc = db.parse(new URL("http://cubs.bluesq.com/cubs/cubs.php?action=getpage&thepage=385.xml").openStream());
doc.getDocumentElement().normalize();
NodeList nodeList = doc.getElementsByTagName("Type");
System.out.println("ukupno:"+nodeList.getLength());
if (nodeList != null && nodeList.getLength() > 0) {
for (int j = 0; j < nodeList.getLength(); j++) {
Element el = (org.w3c.dom.Element) nodeList.item(j);
type_id = Integer.parseInt(el.getAttribute("type_id"));
System.out.println("type id:"+type_id);
}
}
此代码给了我所有的元素,我不希望这样,我希望所有的元素,其中属性TYPE_ID = “4218”!
答
XPath是您正确的选择:
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.parse("<Your xml doc uri>");
XPathFactory xPathfactory = XPathFactory.newInstance();
XPath xpath = xPathfactory.newXPath();
XPathExpression expr = xpath.compile("//Type[@type_id=\"4218\"]");
NodeList nl = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
并遍历nl
答
您可以使用XPath.XPath来浏览XML文档中的元素和属性。在Java中有一些很好的Xpath实现。
为您例如
XPath xpath = XPathFactory.newInstance().newXPath();
XPathExpression expr = xpath.compile("//Type[@type_id=\"4218\"]");
Object exprResult = expr.evaluate(doc, XPathConstants.NODESET);
NodeList nodeList = (NodeList) exprResult;
答
你错过了你的循环内的条件:
if(nodeList != null && nodeList.getLength() > 0){
for (int j = 0; j < nodeList.getLength(); j++) {
Element el = (org.w3c.dom.Element) nodeList.item(j);
if (el.hasAttribute("type_id") && el.getAttribute("type_id").equals("4218")) {
type_id = Integer.parseInt(el.getAttribute("type_id"));
System.out.println("type id:"+type_id);
}
}
}
而且你不需要测试,如果节点列表返回的的getElementsByTagName为空,所以你可以删除如果在循环之前。
在一般情况下,使用XPath可能会更好。
答
以下XPath会给你的类型元素,你是后:
/BSQCUBS/Class/Type[@type_id=4218]
所以,你可以使用以下Java代码来获得仅包含这些代码的NodeList:
XPathExpression expr = xpath.compile("/BSQCUBS/Class/Type[@type_id=4218]");
NodeList nl = (NodeList)expr.evaluate(doc, XPathConstants.NODESET);
答
请按照下面的@soulcheck答案,如果可能的话放一个break语句...以增强您的搜索。
if(nodeList != null && nodeList.getLength() > 0){
for (int j = 0; j < nodeList.getLength(); j++) {
Element el = (org.w3c.dom.Element) nodeList.item(j);
if (el.hasAttribute("type_id") && el.getAttribute("type_id").equals("4218")) {
type_id = Integer.parseInt(el.getAttribute("type_id"));
System.out.println("type id:"+type_id);
break;
}
}
}
我如何寻找价值TYPE_ID与运营商一样 –