Analizador XPath Java - Analizar documento XML
Pasos para usar XPath
A continuación se muestran los pasos que se utilizan al analizar un documento con XPath Parser.
Importe paquetes relacionados con XML.
Cree un DocumentBuilder.
Cree un documento a partir de un archivo o una secuencia.
Cree un objeto XPath y una expresión de ruta XPath.
Compile la expresión XPath usando XPath.compile() y obtener una lista de nodos evaluando la expresión compilada a través de XPath.evaluate().
Itere sobre la lista de nodos.
Examine los atributos.
Examine los subelementos.
Importar paquetes relacionados con XML
import org.w3c.dom.*;
import org.xml.sax.*;
import javax.xml.parsers.*;
import javax.xml.xpath.*;
import java.io.*;
Crear un DocumentBuilder
DocumentBuilderFactory factory =
DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Crear un documento a partir de un archivo o una secuencia
StringBuilder xmlStringBuilder = new StringBuilder();
xmlStringBuilder.append("<?xml version = "1.0"?> <class> </class>");
ByteArrayInputStream input = new ByteArrayInputStream(
xmlStringBuilder.toString().getBytes("UTF-8"));
Document doc = builder.parse(input);
Construir XPath
XPath xPath = XPathFactory.newInstance().newXPath();
Preparar la expresión Path y evaluarla
String expression = "/class/student";
NodeList nodeList = (NodeList) xPath.compile(expression).evaluate(
doc, XPathConstants.NODESET);
Iterar sobre NodeList
for (int i = 0; i < nodeList.getLength(); i++) {
Node nNode = nodeList.item(i);
...
}
Examinar atributos
//returns specific attribute
getAttribute("attributeName");
//returns a Map (table) of names/values
getAttributes();
Examinar subelementos
//returns a list of subelements of specified name
getElementsByTagName("subelementName");
//returns a list of all child nodes
getChildNodes();
Ejemplo de demostración
Aquí está el archivo de texto de entrada que necesitamos analizar:
<?xml version = "1.0"?>
<class>
<student rollno = "393">
<firstname>dinkar</firstname>
<lastname>kad</lastname>
<nickname>dinkar</nickname>
<marks>85</marks>
</student>
<student rollno = "493">
<firstname>Vaneet</firstname>
<lastname>Gupta</lastname>
<nickname>vinni</nickname>
<marks>95</marks>
</student>
<student rollno = "593">
<firstname>jasvir</firstname>
<lastname>singh</lastname>
<nickname>jazz</nickname>
<marks>90</marks>
</student>
</class>
XPathParserDemo.java
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();
}
}
}
Esto produciría el siguiente resultado:
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