[英]parse xml using dom java
我有波纹管xml:
<modelingOutput>
<listOfTopics>
<topic id="1">
<token id="354">wish</token>
</topic>
</listOfTopics>
<rankedDocs>
<topic id="1">
<documents>
<document id="1" numWords="0"/>
<document id="2" numWords="1"/>
<document id="3" numWords="2"/>
</documents>
</topic>
</rankedDocs>
<listOfDocs>
<documents>
<document id="1">
<topic id="1" percentage="4.790644689978203%"/>
<topic id="2" percentage="11.427632949428334%"/>
<topic id="3" percentage="17.86913349249596%"/>
</document>
</documents>
</listOfDocs>
</modelingOutput>
Ι想要解析此xml文件并从ListofDocs获取主题ID和百分比
第一种方法是从xml获取所有文档元素,然后检查祖父节点是否为ListofDocs。 但元素文档存在于RankingDocs和listOfDocs中 ,所以我有一个非常大的列表。
所以我想知道是否存在更好的解决方案来解析这个xml避免if语句?
我的代码:
public void parse(){
Document dom = null;
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
InputSource is = new InputSource(new StringReader(xml));
dom = db.parse(is);
Element doc = dom.getDocumentElement();
NodeList documentnl = doc.getElementsByTagName("document");
for (int i = 1; i <= documentnl.getLength(); i++) {
Node item = documentnl.item(i);
Node parentNode = item.getParentNode();
Node grandpNode = parentNode.getParentNode();
if(grandpNode.getNodeName() == "listOfDocs"{
//get value
}
}
}
首先,在检查节点名称时,不应使用==
比较String
。 始终使用equals
方法。
您可以使用XPath仅评估listOfDocs
下的文档topic
元素:
XPathFactory xPathFactory = XPathFactory.newInstance();
XPath xPath = xPathFactory.newXPath();
XPathExpression xPathExpression = xPath.compile("//listOfDocs//document/topic");
NodeList topicnl = (NodeList) xPathExpression.evaluate(dom, XPathConstants.NODESET);
for(int i = 0; i < topicnl.getLength(); i++) {
...
如果您不想使用if语句,可以使用XPath直接获取所需的元素。
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.parse("source.xml");
XPathFactory xPathfactory = XPathFactory.newInstance();
XPath xpath = xPathfactory.newXPath();
XPathExpression expr = xpath.compile("/*/listOfDocs/documents/document/topic");
NodeList nodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
for (int i = 0; i < nodes.getLength(); i++) {
System.out.println(nodes.item(i).getAttributes().getNamedItem("id"));
System.out.println(nodes.item(i).getAttributes().getNamedItem("percentage"));
}
请在这里查看GitHub项目。
希望这可以帮助。
我喜欢使用XMLBeam执行此类任务:
public class Answer {
@XBDocURL("resource://data.xml")
public interface DataProjection {
public interface Topic {
@XBRead("./@id")
int getID();
@XBRead("./@percentage")
String getPercentage();
}
@XBRead("/modelingOutput/listOfDocs//document/topic")
List<Topic> getTopics();
}
public static void main(final String[] args) throws IOException {
final DataProjection dataProjection = new XBProjector().io().fromURLAnnotation(DataProjection.class);
for (Topic topic : dataProjection.getTopics()) {
System.out.println(topic.getID() + ": " + topic.getPercentage());
}
}
}
甚至有一种方便的方法可以将百分比转换为float
或double
。 告诉我你是否想要一个例子。
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