JAVA操作XML的完整例子——W3C DOM篇

这是一个用JAVA W3C DOM 进行XML操作的例子，包含了查询、增加、修改、删除、保存的基本操作。较完整的描述了一个XML的整个操作流程。适合刚入门JAVA XML操作的朋友参考和学习。

假设有XML文件：test1.xml

<? xml version="1.0" encoding="UTF-8" ?>
< books >
  < book >
   < name > 哈里波特 </ name >
   < price > 10 </ price >
   < memo > 这是一本很好看的书。 </ memo >
  </ book >
  < book  id ="B02" >
   < name > 三国演义 </ name >
   < price > 10 </ price >
   < memo > 四大名著之一。 </ memo >
  </ book >
  < book  id ="B03" >
   < name > 水浒 </ name >
   < price > 6 </ price >
   < memo > 四大名著之一。 </ memo >
  </ book >
  < book  id ="B04" >
   < name > 红楼 </ name >
   < price > 5 </ price >
   < memo > 四大名著之一。 </ memo >
  </ book >
</ books >   

下面是为Test.java

import  java.io.File;
import  java.io.FileNotFoundException;
import  java.io.FileOutputStream;
import  java.io.IOException;

import  org.w3c.dom. * ;
import  org.xml.sax.SAXException;

import  javax.xml.parsers. * ;
import  javax.xml.transform. * ;
import  javax.xml.transform.dom.DOMSource;
import  javax.xml.transform.stream. * ;
import  javax.xml.xpath. * ;

public   class  Test  ... {
     public   static   void  main(String[] args)  ... {
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        Element theBook = null , theElem = null , root = null ;
         try   ... {
            factory.setIgnoringElementContentWhitespace( true );
            
            DocumentBuilder db = factory.newDocumentBuilder();
            Document xmldoc = db.parse( new  File( " Test1.xml " ));
            root = xmldoc.getDocumentElement();
            
             // ---  新建一本书开始 ----
            theBook = xmldoc.createElement( " book " );
            theElem = xmldoc.createElement( " name " );
            theElem.setTextContent( " 新书 " );
            theBook.appendChild(theElem);
            
            theElem = xmldoc.createElement( " price " );
            theElem.setTextContent( " 20 " );
            theBook.appendChild(theElem);

            theElem = xmldoc.createElement( " memo " );
            theElem.setTextContent( " 新书的更好看。 " );
            theBook.appendChild(theElem);
            root.appendChild(theBook);
            System.out.println( " ---  新建一本书开始 ---- " );
            output(xmldoc);
             // ---  新建一本书完成 ----

             // ---  下面对《哈里波特》做一些修改。 ----
             // ---  查询找《哈里波特》----
            theBook = (Element) selectSingleNode( " /books/book[name='哈里波特'] " , root);
            System.out.println( " ---  查询找《哈里波特》 ---- " );
            output(theBook);
             // ---  此时修改这本书的价格 -----
            theBook.getElementsByTagName( " price " ).item( 0 ).setTextContent( " 15 " ); // getElementsByTagName返回的是NodeList，所以要跟上item(0)。另外，getElementsByTagName("price")相当于xpath的".//price"。
            System.out.println( " ---  此时修改这本书的价格 ---- " );
            output(theBook);
             // ---  另外还想加一个属性id，值为B01 ----
            theBook.setAttribute( " id " ,  " B01 " );
            System.out.println( " ---  另外还想加一个属性id，值为B01 ---- " );
            output(theBook);
             // ---  对《哈里波特》修改完成。 ----

             // ---  要用id属性删除《三国演义》这本书  ----
            theBook = (Element) selectSingleNode( " /books/book[@id='B02'] " , root);
            System.out.println( " ---  要用id属性删除《三国演义》这本书 ---- " );
            output(theBook);
            theBook.getParentNode().removeChild(theBook);
            System.out.println( " ---  删除后的ＸＭＬ ---- " );
            output(xmldoc);

             // ---  再将所有价格低于10的书删除  ----
            NodeList someBooks = selectNodes( " /books/book[price<10] " , root);
            System.out.println( " ---  再将所有价格低于10的书删除  --- " );
            System.out.println( " ---  符合条件的书有　 " + someBooks.getLength() + " 本。  --- " );
             for ( int  i = 0 ;i < someBooks.getLength();i ++ )  ... {
                someBooks.item(i).getParentNode().removeChild(someBooks.item(i));
            }
            output(xmldoc);

            saveXml( " Test1_Edited.xml " , xmldoc);
        }   catch  (ParserConfigurationException e)  ... {
            e.printStackTrace();
        }   catch  (SAXException e)  ... {
            e.printStackTrace();
        }   catch  (IOException e)  ... {
            e.printStackTrace();
        }
    }

     public   static   void  output(Node node)  ... { // 将node的XML字符串输出到控制台
        TransformerFactory transFactory = TransformerFactory.newInstance();
         try   ... {
            Transformer transformer  =  transFactory.newTransformer();
            transformer.setOutputProperty( " encoding " ,  " gb2312 " );
            transformer.setOutputProperty( " indent " ,  " yes " );

            DOMSource source = new  DOMSource();
            source.setNode(node);
            StreamResult result = new  StreamResult();
            result.setOutputStream(System.out);
            
            transformer.transform(source, result);
        }   catch  (TransformerConfigurationException e)  ... {
            e.printStackTrace();
        }   catch  (TransformerException e)  ... {
            e.printStackTrace();
        }    
    }
    
     public   static  Node selectSingleNode(String express, Object source)  ... { // 查找节点，并返回第一个符合条件节点
        Node result = null ;
        XPathFactory xpathFactory = XPathFactory.newInstance();
        XPath xpath = xpathFactory.newXPath();
         try   ... {
            result = (Node) xpath.evaluate(express, source, XPathConstants.NODE);
        }   catch  (XPathExpressionException e)  ... {
            e.printStackTrace();
        }
        
         return  result;
    }
    
     public   static  NodeList selectNodes(String express, Object source)  ... { // 查找节点，返回符合条件的节点集。
        NodeList result = null ;
        XPathFactory xpathFactory = XPathFactory.newInstance();
        XPath xpath = xpathFactory.newXPath();
         try   ... {
            result = (NodeList) xpath.evaluate(express, source, XPathConstants.NODESET);
        }   catch  (XPathExpressionException e)  ... {
            e.printStackTrace();
        }
        
         return  result;
    }
    
     public   static   void  saveXml(String fileName, Document doc)  ... { // 将Document输出到文件
        TransformerFactory transFactory = TransformerFactory.newInstance();
         try   ... {
            Transformer transformer  =  transFactory.newTransformer();
            transformer.setOutputProperty( " indent " ,  " yes " );

            DOMSource source = new  DOMSource();
            source.setNode(doc);
            StreamResult result = new  StreamResult();
            result.setOutputStream( new  FileOutputStream(fileName));
            
            transformer.transform(source, result);
        }   catch  (TransformerConfigurationException e)  ... {
            e.printStackTrace();
        }   catch  (TransformerException e)  ... {
            e.printStackTrace();
        }   catch  (FileNotFoundException e)  ... {
            e.printStackTrace();
        }    
    }
}