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HomeBackend DevelopmentXML/RSS TutorialJava reading and parsing xml file example

Read the local xml file and parse it through DOM. The characteristic of DOM parsing is to load the entire xml file into the memory to form a DOM tree structure. The tree structure is convenient for traversal and manipulation.

The characteristic of DOM parsing is to read the xml file and convert it into a dom tree structure, which is traversed through the nodes.

This is W3c’s concept of nodes

If the xml contains a large amount of data, due to the feature of dom loading the xml into the memory at one time, the dom is not suitable for containing a large amount of data. xml parsing. When a large amount of xml is included, parsing with SAX saves memory.

The following is an example of using DOM to parse xml files:

The xml file structure is as follows:

<?xml version="1.0" encoding="ISO-8859-1"?>
<bookstore>
 <book category="cooking">
 <title>Everyday Italian</title>
 <author>Giada De Laurentiis</author>
 <year>2005</year>
 <price>30.00</price>
 </book>
 <book category="children">
 <title>Harry Potter</title>
 <author>J K. Rowling</author>
 <year>2005</year>
 <price>29.99</price>
 </book>
 <book category="web">
 <title>XQuery Kick Start</title>
 <author>James McGovern</author>
 <year>2003</year>
 <price>49.99</price>
 </book>
 <book category="web" cover="paperback">
 <title>Learning XML</title>
 <author>Erik T. Ray</author>
 <year>2003</year>
 <price>39.95</price>
 </book>
</bookstore>

Create a class to parse xml as follows:

package xml.dom;
 
import java.io.File;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
 
public class ReadXmlFile {
  
 public static void main(String[] args) {
  
 try{
   
  File xmlFile = new File("src/resource/book.xml");
   
  DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
   
  DocumentBuilder builder = builderFactory.newDocumentBuilder();
   
  Document doc = builder.parse(xmlFile);
   
  doc.getDocumentElement().normalize();
   
  System.out.println("Root element: "+doc.getDocumentElement().getNodeName());
   
  NodeList nList = doc.getElementsByTagName("book");
   
  for(int i = 0 ; i<nList.getLength();i++){
   
  Node node = nList.item(i);
   
  System.out.println("Node name: "+ node.getNodeName());
  Element ele = (Element)node;
   
  System.out.println("----------------------------");
  if(node.getNodeType() == Element.ELEMENT_NODE){
   
  System.out.println("book category: "+ ele.getAttribute("category"));
   
  System.out.println("title name: "+ ele.getElementsByTagName("title").item(0).getTextContent());
   
  System.out.println("author name: "+ele.getElementsByTagName("author").item(0).getTextContent());
   
  System.out.println("year :"+ele.getElementsByTagName("year").item(0).getTextContent());
   
  System.out.println("price : "+ele.getElementsByTagName("price").item(0).getTextContent());
   
  System.out.println("-------------------------");
   
   
  }
   
   
  }

Analysis results:

Root element: bookstore
Node name: book
----------------------------
book category: cooking
title name: Everyday Italian
author name: Giada De Laurentiis
year :2005
price : 30.00
-------------------------
Node name: book
----------------------------
book category: children
title name: Harry Potter
author name: J K. Rowling
year :2005
price : 29.99
-------------------------
Node name: book
----------------------------
book category: web
title name: XQuery Kick Start
author name: James McGovern
year :2003
price : 49.99
-------------------------
Node name: book
----------------------------
book category: web
title name: Learning XML
author name: Erik T. Ray
year :2003
price : 39.95
-------------------------

The above is to obtain the corresponding value through name,
The following is output using the loop node method:
The code for the loop node output method is as follows:

package xml.dom;
 
import java.io.File;
 
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
 
import org.w3c.dom.Document;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
 
public class ReadXmlFile2 {
  
 public static void main(String[] args) {
 try{
   
  File xmlFile = new File("src/resource/book.xml");
   
  DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
   
  DocumentBuilder builder = builderFactory.newDocumentBuilder();
   
  Document doc = builder.parse(xmlFile);
   
  doc.getDocumentElement().normalize();
   
  System.out.println("Root element: "+doc.getDocumentElement().getNodeName());
   
   
  if(doc.hasChildNodes()){
   
  printNode(doc.getChildNodes());
  }
 }catch(Exception e){
  
 e.printStackTrace();
  
 }
  
 }
  
 public static void printNode(NodeList nodeList){
 System.out.println("------------------------");
 // System.out.println(nodeList.getLength());
 for(int i = 0; i<nodeList.getLength(); i++){
  
 Node node = (Node)nodeList.item(i);
  
  
 if(node.getNodeType() == Node.ELEMENT_NODE){
  
 System.out.println("node name: "+node.getNodeName());
  
 System.out.println("node value: "+node.getTextContent());
  
 if(node.hasAttributes()){
  NamedNodeMap nodeMap = node.getAttributes();
   
  for(int j = 0; j < nodeMap.getLength() ; j++){
   
  Node nodenew = nodeMap.item(j);
   
  System.out.println("node name "+nodenew.getNodeName());
  System.out.println("node value "+nodenew.getNodeValue());
  }
 }
 if(node.hasChildNodes()){
  printNode(node.getChildNodes());
 }
 }
  
 }
  
 }
 
}

Output result As follows:

Root element: bookstore
------------------------
node name: bookstore
node value: 
  
 Everyday Italian
 Giada De Laurentiis
 2005
 30.00
  
  
 Harry Potter
 J K. Rowling
 2005
 29.99
  
  
 XQuery Kick Start
 James McGovern
 2003
 49.99
  
  
 Learning XML
 Erik T. Ray
 2003
 39.95
  
 
------------------------
node name: book
node value: 
 Everyday Italian
 Giada De Laurentiis
 2005
 30.00
  
node name category
node value cooking
------------------------
node name: title
node value: Everyday Italian
node name lang
node value en
------------------------
node name: author
node value: Giada De Laurentiis
------------------------
node name: year
node value: 2005
------------------------
node name: price
node value: 30.00
------------------------
node name: book
node value: 
 Harry Potter
 J K. Rowling
 2005
 29.99
  
node name category
node value children
------------------------
node name: title
node value: Harry Potter
node name lang
node value en
------------------------
node name: author
node value: J K. Rowling
------------------------
node name: year
node value: 2005
------------------------
node name: price
node value: 29.99
------------------------
node name: book
node value: 
 XQuery Kick Start
 James McGovern
 2003
 49.99
  
node name category
node value web
------------------------
node name: title
node value: XQuery Kick Start
node name lang
node value en
------------------------
node name: author
node value: James McGovern
------------------------
node name: year
node value: 2003
------------------------
node name: price
node value: 49.99
------------------------
node name: book
node value: 
 Learning XML
 Erik T. Ray
 2003
 39.95
  
node name category
node value web
node name cover
node value paperback
------------------------
node name: title
node value: Learning XML
node name lang
node value en
------------------------
node name: author
node value: Erik T. Ray
------------------------
node name: year
node value: 2003
------------------------
node name: price
node value: 39.95
------------------------

Questions about nodes:

<book category="cooking">
<title>Everyday Italian</title>
<author>Giada De Laurentiis</author>
<year>2005</year>
<price>30.00</price>
</book>

For book applications: doc.getChildNodes() gets a NodeList where the length of the NodeList is 9
The 9 nodes are as follows:
title node
lang node
Everyday node
author node
Giada De Laurentiis node
year node
2005 node
price node
30.00 node

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