讀取本地的xml文件，通過(guò)DOM進(jìn)行解析，DOM解析的特點(diǎn)就是把整個(gè)xml文件裝載入內(nèi)存中，形成一顆DOM樹(shù)形結(jié)構(gòu)，樹(shù)結(jié)構(gòu)是方便遍歷和和操縱。
DOM解析的特性就是讀取xml文件轉(zhuǎn)換為 dom樹(shù)形結(jié)構(gòu)，通過(guò)節(jié)點(diǎn)進(jìn)行遍歷。
這是W3c關(guān)于節(jié)點(diǎn)的概念
如果xml中包含有大量的數(shù)據(jù)，由于dom一次性把xml裝入內(nèi)存中的特性，所以dom不適合于包含大量數(shù)據(jù)的xml解析。當(dāng)包含有大量xml的時(shí)候，用SAX進(jìn)行解析比較節(jié)省內(nèi)存。
下面是一個(gè)運(yùn)用DOM進(jìn)行解析xml文件的例子：
xml文件結(jié)構(gòu)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> |
創(chuàng)建解析xml的類如下：
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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("-------------------------"); } } |
解析結(jié)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------------------------- |
以上是通過(guò)name獲得對(duì)應(yīng)的值，
下面利用循環(huán)節(jié)點(diǎn)的方式輸出：
循環(huán)節(jié)點(diǎn)輸出方式的代碼如下：
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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()); } } } }} |
輸出結(jié)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------------------------ |
關(guān)于節(jié)點(diǎn)的問(wèn)題：
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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> |
對(duì)于 book應(yīng)用：doc.getChildNodes() 得到一個(gè)NodeList其中NodeList的長(zhǎng)度為9
9個(gè)節(jié)點(diǎn)分別如下：
title節(jié)點(diǎn)
lang節(jié)點(diǎn)
Everyday節(jié)點(diǎn)
author節(jié)點(diǎn)
Giada De Laurentiis節(jié)點(diǎn)
year節(jié)點(diǎn)
2005節(jié)點(diǎn)
price節(jié)點(diǎn)
30.00節(jié)點(diǎn)
