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 >
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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( "-------------------------" );
}
}
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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
-------------------------
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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());
}
}
}
}
}
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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
------------------------
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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>
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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