读取本地的xml文件，通过DOM进行解析，DOM解析的特点就是把整个xml文件装载入内存中，形成一颗DOM树形结构，树结构是方便遍历和和操纵。
DOM解析的特性就是读取xml文件转换为 dom树形结构，通过节点进行遍历。
这是W3c关于节点的概念
如果xml中包含有大量的数据，由于dom一次性把xml装入内存中的特性，所以dom不适合于包含大量数据的xml解析。当包含有大量xml的时候，用SAX进行解析比较节省内存。
下面是一个运用DOM进行解析xml文件的例子：
xml文件结构如下：
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<?xml version="1.0" encoding="ISO-8859-1"?><bookstore> <book category="cooking"> <title lang="en">Everyday Italian</title> <author>Giada De Laurentiis</author> <year>2005</year> <price>30.00</price> </book> <book category="children"> <title lang="en">Harry Potter</title> <author>J K. Rowling</author> <year>2005</year> <price>29.99</price> </book> <book category="web"> <title lang="en">XQuery Kick Start</title> <author>James McGovern</author> <year>2003</year> <price>49.99</price> </book> <book category="web" cover="paperback"> <title lang="en">Learning XML</title> <author>Erik T. Ray</author> <year>2003</year> <price>39.95</price> </book></bookstore> |
创建解析xml的类如下：
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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("-------------------------"); } } |
解析结果：
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Root element: bookstoreNode name: book----------------------------book category: cookingtitle name: Everyday Italianauthor name: Giada De Laurentiisyear :2005price : 30.00-------------------------Node name: book----------------------------book category: childrentitle name: Harry Potterauthor name: J K. Rowlingyear :2005price : 29.99-------------------------Node name: book----------------------------book category: webtitle name: XQuery Kick Startauthor name: James McGovernyear :2003price : 49.99-------------------------Node name: book----------------------------book category: webtitle name: Learning XMLauthor name: Erik T. Rayyear :2003price : 39.95------------------------- |
以上是通过name获得对应的值，
下面利用循环节点的方式输出：
循环节点输出方式的代码如下：
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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()); } } } }} |
输出结果如下：
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Root element: bookstore------------------------node name: bookstorenode 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: booknode value: Everyday Italian Giada De Laurentiis 2005 30.00 node name categorynode value cooking------------------------node name: titlenode value: Everyday Italiannode name langnode value en------------------------node name: authornode value: Giada De Laurentiis------------------------node name: yearnode value: 2005------------------------node name: pricenode value: 30.00------------------------node name: booknode value: Harry Potter J K. Rowling 2005 29.99 node name categorynode value children------------------------node name: titlenode value: Harry Potternode name langnode value en------------------------node name: authornode value: J K. Rowling------------------------node name: yearnode value: 2005------------------------node name: pricenode value: 29.99------------------------node name: booknode value: XQuery Kick Start James McGovern 2003 49.99 node name categorynode value web------------------------node name: titlenode value: XQuery Kick Startnode name langnode value en------------------------node name: authornode value: James McGovern------------------------node name: yearnode value: 2003------------------------node name: pricenode value: 49.99------------------------node name: booknode value: Learning XML Erik T. Ray 2003 39.95 node name categorynode value webnode name covernode value paperback------------------------node name: titlenode value: Learning XMLnode name langnode value en------------------------node name: authornode value: Erik T. Ray------------------------node name: yearnode value: 2003------------------------node name: pricenode value: 39.95------------------------ |
关于节点的问题：
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<book category="cooking"><title lang="en">Everyday Italian</title><author>Giada De Laurentiis</author><year>2005</year><price>30.00</price></book> |
对于 book应用：doc.getChildNodes() 得到一个NodeList其中NodeList的长度为9
9个节点分别如下：
title节点
lang节点
Everyday节点
author节点
Giada De Laurentiis节点
year节点
2005节点
price节点
30.00节点
