讀取本地的xml文件，透過DOM解析，DOM解析的特點就是把整個xml文件裝載入記憶體中，形成一顆DOM樹形結構，樹結構是方便遍歷和操縱。
DOM解析的特性就是讀取xml檔轉換為 dom樹狀結構，透過節點進行遍歷。
這是W3c關於節點的概念
如果xml中包含有大量的數據，由於dom一次把xml裝入內存中的特性，所以dom不適合包含大量數據的xml解析。當包含有大量xml的時候，用SAX進行解析比較節省記憶體。
下面是一個運用DOM進行解析xml檔的範例：
xml檔結構如下：
<?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>
建立解析xml的類別如下：
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("-------------------------");
}
}解析結果：
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 -------------------------
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());
}
}
}
}
}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 ------------------------
輸出結果如下：
<book category="cooking"> <title>Everyday Italian</title> <author>Giada De Laurentiis</author> <year>2005</year> <price>30.00</price> </book>
關於節點的問題：
rrreee對於book應用：doc.getChildNodes() 得到一個NodeListreee
對於book應用：doc.getChildNodes() 得到一個Node其中NodeListreee
對於book應用：doc.getChildNodes() 得到一個NodeListreee？長度為9
9個節點分別如下：
title節點
lang節點
Everyday節點
author節點
Giada De Laurentiis節點
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