dom解析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();
        }
    }
}