DOM的概念和简单应用：使用DOM解析XML数据

2022-09-29 20:51:26

概念：DOM是Document Object Model的简称，即文档数据模型。

Oracle公司提供了JAXP（Java API for XML Processing）来解析XML。JAXP会把XML文档转换成一个DOM树，JAXP的三个包都在JDK中。

org.w3c.dom;W3C推荐的解析文档的接口

org.xml.sax;使用SAX解析XML文档的接口

javax.xml.parsers;解析器工厂工具

一、使用DOM解析XML文档的步骤

1.创建解析器工厂对象，即DocumentBuilderFactory对象

2.由解析器工厂创建解析器对象，即DocumentBuilder对象

3.由解析器对象解析XML文档构建相应的DOM树，创建Document对象

4.以Document对象为起点对DOM树的节点进行增加、删除、修改、查询等操作

5.保存XML数据文档

二、案例

 <?xml version="1.0" encoding="GB2312" standalone="no"?>

 <PhoneInfo>

     <Brand name="华为">

         <Type name="P9" />

         <Item>

             <title>标题信息</title>

             <link>连接</link>

             <description>描述</description>

             <pubDate>2016-11-12</pubDate>

         </Item>

     </Brand>

     <Brand name="苹果">

         <Type name="iPhone5" />

         <Type name="iPhone6" />

     </Brand>

     <Brand name="SAMSUNG">

         <Type name="Note7" />

     </Brand>

     <Brand name="SAMSUNG">

         <Type name="Note7" />

     </Brand>

     <Brand name="三星">

         <Type name="Note7" />

     </Brand>

     <Brand name="三星">

         <Type name="Note7" />

     </Brand>

 </PhoneInfo>

1.使用DOM读取手机收藏信息

 import java.io.IOException;

 import javax.xml.parsers.DocumentBuilder;

 import javax.xml.parsers.DocumentBuilderFactory;

 import javax.xml.parsers.ParserConfigurationException;

 import org.w3c.dom.Document;

 import org.w3c.dom.Element;

 import org.w3c.dom.Node;

 import org.w3c.dom.NodeList;

 import org.xml.sax.SAXException;

 /**

  * DOM解析xml文档

  * @author Administrator

  *

  */

 public class PhoneInfoShow {

     public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException{

         //得到DOM解析器的工厂实例

         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

         //从DOM工厂获得DOM解析器

         DocumentBuilder builder = dbf.newDocumentBuilder();

         //解析xml文档，得到一个Document对象，即DOM树

         Document phoneInfo = builder.parse("src/PhoneInfo.xml");

         //得到所有Brand节点列表信息

         NodeList brandList = phoneInfo.getElementsByTagName("Brand");

         //循环Brand信息

         for (int i = 0; i < brandList.getLength(); i++) {

             //获取第i个Brand元素信息

             Node node = brandList.item(i);

             Element brand = (Element)node;

             //获取元素属性值

             String brandValue = brand.getAttribute("name");

             System.out.println("手机品牌："+brandValue);

             //获取brand元素下的所有子元素

             NodeList types = brand.getElementsByTagName("Type");

             for (int j = 0; j < types.getLength(); j++) {

                 /*Node item = types.item(j);

                 Element type = (Element)item;*/

                 Element type = (Element)types.item(j);

                 //获取子节点属性值

                 String typeValue = type.getAttribute("name");

                 System.out.println("\t型号："+typeValue);

             }

         }

     }

 }

2.查找节点信息

 /**

  * 查找节点信息

  * @author Administrator

  *

  */

 public class PhoneInfo03{

     public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException {

         //得到DOM解析器工厂

         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

         //从DOM工厂获得DOM解析器

         DocumentBuilder db = dbf.newDocumentBuilder();

         //解析XML文档得到一个DOM树

         Document phoneInfo = db.parse(new File("src/PhoneInfo.xml"));

         //读取pubDate

         NodeList list = phoneInfo.getElementsByTagName("pubDate");

         //pubDate元素节点（转换）

         Element pubDateElement = (Element)list.item(0);

         //读取文本节点

         String pubDate = pubDateElement.getFirstChild().getNodeValue();

         System.out.println(pubDate);

     }

 }

三、使用DOM维护XML数据

1.添加信息

 import java.io.FileOutputStream;

 import java.io.IOException;

 import javax.xml.parsers.DocumentBuilder;

 import javax.xml.parsers.DocumentBuilderFactory;

 import javax.xml.parsers.ParserConfigurationException;

 import javax.xml.transform.OutputKeys;

 import javax.xml.transform.Transformer;

 import javax.xml.transform.TransformerException;

 import javax.xml.transform.TransformerFactory;

 import javax.xml.transform.dom.DOMSource;

 import javax.xml.transform.stream.StreamResult;

 import org.w3c.dom.Document;

 import org.w3c.dom.Element;

 import org.xml.sax.SAXException;

 /**

  * 添加手机收藏信息

  * @author Administrator

  *

  */

 public class PhoneInfoAdd {

     public static void main(String[] args) throws TransformerException, SAXException, IOException, ParserConfigurationException {

         //解析器工厂

         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

         //解析器

         DocumentBuilder db = dbf.newDocumentBuilder();

         //DOM文档

         Document phone = db.parse("src/PhoneInfo.xml");

         /*创建brand节点*/

         Element brand = phone.createElement("Brand");

         brand.setAttribute("name","三星");

         /*创建type节点*/

         Element type = phone.createElement("Type");

         type.setAttribute("name", "Note7");

         //建立父子关系

         brand.appendChild(type);

         Element phoneElement = (Element)phone.getElementsByTagName("PhoneInfo").item(0);

         phoneElement.appendChild(brand);

         //保存xml文件

         /*使用传输工厂*/

         TransformerFactory transformerFactory = TransformerFactory.newInstance();

         Transformer transformer = transformerFactory.newTransformer();

         /*创建数据源*/

         DOMSource domSource = new DOMSource(phone);

         /*设置编码类型*/

         transformer.setOutputProperty(OutputKeys.ENCODING, "gb2312");

         /*创建目标数据*/

         StreamResult result = new StreamResult(new FileOutputStream("src/PhoneInfo.xml"));

         /*把DOM树转换为xml文件*/

         transformer.transform(domSource, result);

     }

 }

2.修改信息

 import java.io.FileOutputStream;

 import java.io.IOException;

 import javax.xml.parsers.DocumentBuilder;

 import javax.xml.parsers.DocumentBuilderFactory;

 import javax.xml.parsers.ParserConfigurationException;

 import javax.xml.transform.OutputKeys;

 import javax.xml.transform.Result;

 import javax.xml.transform.Transformer;

 import javax.xml.transform.TransformerException;

 import javax.xml.transform.TransformerFactory;

 import javax.xml.transform.dom.DOMSource;

 import javax.xml.transform.stream.StreamResult;

 import org.w3c.dom.Document;

 import org.w3c.dom.Element;

 import org.w3c.dom.NodeList;

 import org.xml.sax.SAXException;

 public class PhoneInfoEdit {

     public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException, TransformerException {

         //解析xml得到DOM对象

         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

         DocumentBuilder db = dbf.newDocumentBuilder();

         Document phone = db.parse("src/PhoneInfo.xml");

         //找到修改的菜单

         NodeList brand = phone.getElementsByTagName("Brand");

         for (int i = 0; i < brand.getLength(); i++) {

             Element brandElement = (Element)brand.item(i);

             //得到Brand的name属性

             String brandName = brandElement.getAttribute("name");

             if ("三星".equals(brandName)) {

                 brandElement.setAttribute("name","SAMSUNG");

             }

         }

         //保存xml文件

         TransformerFactory transformerFactory = TransformerFactory.newInstance();

         Transformer transformer = transformerFactory.newTransformer();

         /*创建DOM源*/

         DOMSource xmlSource = new DOMSource(phone);

         /*设置编码类型*/

         transformer.setOutputProperty(OutputKeys.ENCODING,"gb2312");

         Result outputTarget = new StreamResult(new FileOutputStream("src/PhoneInfo.xml"));

         //写入文件

         transformer.transform(xmlSource, outputTarget );

     }

 }

3.删除信息

 import java.io.FileOutputStream;

 import java.io.IOException;

 import javax.xml.parsers.DocumentBuilder;

 import javax.xml.parsers.DocumentBuilderFactory;

 import javax.xml.parsers.ParserConfigurationException;

 import javax.xml.transform.OutputKeys;

 import javax.xml.transform.Result;

 import javax.xml.transform.Transformer;

 import javax.xml.transform.TransformerException;

 import javax.xml.transform.TransformerFactory;

 import javax.xml.transform.dom.DOMSource;

 import javax.xml.transform.stream.StreamResult;

 import org.w3c.dom.Document;

 import org.w3c.dom.Element;

 import org.w3c.dom.NodeList;

 import org.xml.sax.SAXException;

 /**

  * 删除节点

  * @author Administrator

  *

  */

 public class PhoneInfoDel {

     public static void main(String[] args) throws SAXException, IOException, ParserConfigurationException, TransformerException {

         //解析xml文档

         DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();

         DocumentBuilder documentBuilder = builderFactory.newDocumentBuilder();

         Document phone = documentBuilder.parse("src/PhoneInfo.xml");

         //找到要删除的节点

         NodeList brand = phone.getElementsByTagName("Brand");

         //通过遍历Brand找到要删除的节点

         for (int i = 0; i < brand.getLength(); i++) {

             Element brandElement = (Element)brand.item(i);

             //获取Brand节点属性

             String brandName = brandElement.getAttribute("name");

             //查找需要的节点

             if ("SAMSUNG".equals(brandName)) {

                 //获取父节点，利用父节点删除这个节点

                 brandElement.getParentNode().removeChild(brandElement);

             }

         }

         /*for (int i = 0; i < brand.getLength(); i++) {

             Element brandElement = (Element)brand.item(i);

             //得到Brand的name属性

             String brandName = brandElement.getAttribute("name");

             if ("三星".equals(brandName)) {

                 //修改属性

                 brandElement.setAttribute("name","SAMSUNG");

                 //获取父节点，利用父节点删除这个节点

                 brandElement.getParentNode().removeChild(brandElement);

             }

         }*/

         //写入xml

         TransformerFactory transformerFactory = TransformerFactory.newInstance();

         Transformer transformer = transformerFactory.newTransformer();

         DOMSource xmlSource = new DOMSource(phone);

         //设置编码

         transformer.setOutputProperty(OutputKeys.ENCODING,"gb2312");

         Result outputTarget = new StreamResult(new FileOutputStream("src/PhoneInfo.xml"));

         transformer.transform(xmlSource, outputTarget);

         /*TransformerFactory transformerFactory = TransformerFactory.newInstance();

         Transformer transformer = transformerFactory.newTransformer();

         创建DOM源

         DOMSource xmlSource = new DOMSource(phone);

         设置编码类型

         transformer.setOutputProperty(OutputKeys.ENCODING,"gb2312");

         Result outputTarget = new StreamResult(new FileOutputStream("src/PhoneInfo.xml"));

         //写入文件

         transformer.transform(xmlSource, outputTarget );*/

     }

 }

此外，还可以使用DOM4J解析XML文档会更加方便。

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