📅  最后修改于: 2020-11-14 10:30:52             🧑  作者: Mango
以下是使用XPath Parser解析文档时使用的步骤。
导入与XML相关的包。
创建一个DocumentBuilder。
从文件或流创建文档。
创建一个Xpath对象和一个XPath路径表达式。
使用XPath.compile()编译XPath表达式,并通过XPath.evaluate()评估编译后的表达式,从而获得节点列表。
遍历节点列表。
检查属性。
检查子元素。
import org.w3c.dom.*;
import org.xml.sax.*;
import javax.xml.parsers.*;
import javax.xml.xpath.*;
import java.io.*;
DocumentBuilderFactory factory =
DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
StringBuilder xmlStringBuilder = new StringBuilder();
xmlStringBuilder.append(" ");
ByteArrayInputStream input = new ByteArrayInputStream(
xmlStringBuilder.toString().getBytes("UTF-8"));
Document doc = builder.parse(input);
XPath xPath = XPathFactory.newInstance().newXPath();
String expression = "/class/student";
NodeList nodeList = (NodeList) xPath.compile(expression).evaluate(
doc, XPathConstants.NODESET);
for (int i = 0; i < nodeList.getLength(); i++) {
Node nNode = nodeList.item(i);
...
}
//returns specific attribute
getAttribute("attributeName");
//returns a Map (table) of names/values
getAttributes();
//returns a list of subelements of specified name
getElementsByTagName("subelementName");
//returns a list of all child nodes
getChildNodes();
这是我们需要解析的输入文本文件-
dinkar
kad
dinkar
85
Vaneet
Gupta
vinni
95
jasvir
singh
jazz
90
package com.tutorialspoint.xml;
import java.io.File;
import java.io.IOException;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.w3c.dom.Node;
import org.w3c.dom.Element;
import org.xml.sax.SAXException;
public class XPathParserDemo {
public static void main(String[] args) {
try {
File inputFile = new File("input.txt");
DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder;
dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(inputFile);
doc.getDocumentElement().normalize();
XPath xPath = XPathFactory.newInstance().newXPath();
String expression = "/class/student";
NodeList nodeList = (NodeList) xPath.compile(expression).evaluate(
doc, XPathConstants.NODESET);
for (int i = 0; i < nodeList.getLength(); i++) {
Node nNode = nodeList.item(i);
System.out.println("\nCurrent Element :" + nNode.getNodeName());
if (nNode.getNodeType() == Node.ELEMENT_NODE) {
Element eElement = (Element) nNode;
System.out.println("Student roll no :" + eElement.getAttribute("rollno"));
System.out.println("First Name : "
+ eElement
.getElementsByTagName("firstname")
.item(0)
.getTextContent());
System.out.println("Last Name : "
+ eElement
.getElementsByTagName("lastname")
.item(0)
.getTextContent());
System.out.println("Nick Name : "
+ eElement
.getElementsByTagName("nickname")
.item(0)
.getTextContent());
System.out.println("Marks : "
+ eElement
.getElementsByTagName("marks")
.item(0)
.getTextContent());
}
}
} catch (ParserConfigurationException e) {
e.printStackTrace();
} catch (SAXException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (XPathExpressionException e) {
e.printStackTrace();
}
}
}
这将产生以下结果-
Current Element :student
Student roll no : 393
First Name : dinkar
Last Name : kad
Nick Name : dinkar
Marks : 85
Current Element :student
Student roll no : 493
First Name : Vaneet
Last Name : Gupta
Nick Name : vinni
Marks : 95
Current Element :student
Student roll no : 593
First Name : jasvir
Last Name : singh
Nick Name : jazz
Marks : 90