讀取本地的xml文件，透過DOM解析，DOM解析的特性就是把整個xml檔裝入記憶體中，形成一顆DOM樹狀結構，樹結構是方便遍歷和操縱。
DOM解析的特性就是讀取xml檔轉換成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包含有大量的數據，由於dom一次把xml裝入記憶體中的特性，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文件結構如下：
<?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>
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 orgdom.Element;import orgdom.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: 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-------------------------
以上是透過name獲得對應的值，
下面利用循環節點的方式輸出：
循環節點輸出方式的程式碼如下：
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.NamedNodeMap; .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(); DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance(); DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance(); DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance(); 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()){ NamedMap 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()); } } } }}輸出結果如下：
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------------------------
關於節點的問題：
<book category="cooking"> <title lang="en">Everyday Italian</title> <author>Giada De Laurentiis</author> <year>2005</year> <price>30.00</price> </ book>
對於book應用程式：doc.getChildNodes() 得到一個NodeList其中NodeList的長度為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
year節點
2005節點
price節點
30.00節點