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: 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 ------------------------- |
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: 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 ------------------------ |
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