dom4j读写xml文件

首先我们给出一段示例程序：

import  java.io.File;
import  java.io.FileWriter;
import  java.util.Iterator;

import  org.dom4j.Document;
import  org.dom4j.DocumentHelper;
import  org.dom4j.Element;
import  org.dom4j.io.OutputFormat;
import  org.dom4j.io.SAXReader;
import  org.dom4j.io.XMLWriter;

public   class  DOM4JTest  {

     /** */ /**   */
     /** */ /**   */
     /** */ /**   */
     /** */ /**
     * DOM4J读写XML示例
     * 
     *  @param  args
     *  @throws  Exception
      */
     public   static   void  main(String[] args)  {
         try   {
            XMLWriter writer  =   null ; //  声明写XML的对象
            SAXReader reader  =   new  SAXReader();

            OutputFormat format  =  OutputFormat.createPrettyPrint();
            format.setEncoding( " GBK " ); //  设置XML文件的编码格式

            String filePath  =   " d://student.xml " ;
            File file  =   new  File(filePath);
             if  (file.exists())  {
                Document document  =  reader.read(file); //  读取XML文件
                Element root  =  document.getRootElement(); //  得到根节点
                 boolean  bl  =   false ;
                 for  (Iterator i  =  root.elementIterator( " 学生 " ); i.hasNext();)  {
                    Element student  =  (Element) i.next();
                     if  (student.attributeValue( " sid " ).equals( " 001 " ))  {
                         //  修改学生sid=001的学生信息
                        student.selectSingleNode( " 姓名 " ).setText( " 王五 " );
                        student.selectSingleNode( " 年龄 " ).setText( " 25 " );

                        writer  =   new  XMLWriter( new  FileWriter(filePath), format);
                        writer.write(document);
                        writer.close();
                        bl  =   true ;
                         break ;
                    }
                }
                 if  (bl)  {
                     //  添加一个学生信息
                    Element student  =  root.addElement( " 学生 " );
                    student.addAttribute( " sid " ,  " 100 " );
                    Element sid  =  student.addElement( " 编号 " );
                    sid.setText( " 100 " );
                    Element name  =  student.addElement( " 姓名 " );
                    name.setText( " 嘎嘎 " );
                    Element sex  =  student.addElement( " 性别 " );
                    sex.setText( " 男 " );
                    Element age  =  student.addElement( " 年龄 " );
                    age.setText( " 21 " );

                    writer  =   new  XMLWriter( new  FileWriter(filePath), format);
                    writer.write(document);
                    writer.close();
                }
            }   else   {
                 //  新建student.xml文件并新增内容
                Document _document  =  DocumentHelper.createDocument();
                Element _root  =  _document.addElement( " 学生信息 " );
                Element _student  =  _root.addElement( " 学生 " );
                _student.addAttribute( " sid " ,  " 001 " );
                Element _id  =  _student.addElement( " 编号 " );
                _id.setText( " 001 " );
                Element _name  =  _student.addElement( " 姓名 " );
                _name.setText( " 灰机 " );
                Element _age  =  _student.addElement( " 年龄 " );
                _age.setText( " 18 " );

                writer  =   new  XMLWriter( new  FileWriter(file), format);
                writer.write(_document);
                writer.close();
            }
            System.out.println( " 操作结束!  " );
        }   catch  (Exception e)  {
            e.printStackTrace();
        }

    }
}

执行结果应该是这样：



循环解析节点：

private   void  getAllNodes(String xml)  {
         try   {
            Document authtmp  =  DocumentHelper.parseText(xml);
            List < Element >  list  =  authtmp.selectNodes( " //sms/node " );
             for  ( int  j  =   0 ; j  <  list.size(); j ++ )  {
                Element node  =  (Element) list.get(j);
                nodeByNodes(node);
            }
        }   catch  (Exception e)  {
            e.printStackTrace();
        }
    }

     private   void  nodeByNodes(Element node)  {
         if  (node.element( " node " )  !=   null )  {
            String id  =  node.attributeValue( " id " );
            String name  =  node.attributeValue( " name " );
            System.out.print(id  +   " ------- " );
            System.out.println(name);
             for  (Iterator i  =  node.elementIterator( " node " ); i.hasNext();)  {
                Element newNode  =  (Element) i.next();
                nodeByNodes(newNode);
            }
        }   else   {
            String id  =  node.attributeValue( " id " );
            String name  =  node.attributeValue( " name " );
            System.out.print(id  +   " ------- " );
            System.out.println(name);
        }
    }

其次DOM4J的解释

一.Document对象相关

1.读取XML文件,获得document对象.

      SAXReader reader =   new SAXReader();
      Document   document  =  reader.read( new  File( " input.xml " ));

2.解析XML形式的文本,得到document对象.

       String text  =   " <members></members> ";
      Document document  =  DocumentHelper.parseText(text);

3.主动创建document对象.

      Document document  = DocumentHelper.createDocument();
      Element root  =  document.addElement( " members " ); //  创建根节点

二.节点相关

1.获取文档的根节点.

      Element rootElm  =  document.getRootElement();

2.取得某节点的单个子节点.

      Element memberElm = root.element( " member " ); //  "member"是节点名

3.取得节点的文字

      String text = memberElm.getText();

也可以用:

      String text = root.elementText( " name " );

这个是取得根节点下的name字节点的文字.

4.取得某节点下名为"member"的所有字节点并进行遍历.

List nodes  =  rootElm.elements( " member ");

for  (Iterator it  =  nodes.iterator(); it.hasNext();)  {
    Element elm  = (Element) it.next();
    //  do something
}

5.对某节点下的所有子节点进行遍历.

  for (Iterator it = root.elementIterator();it.hasNext();) {
                 Element element  =  (Element) it.next();
                 //  do something
             }

6.在某节点下添加子节点.

Element ageElm = newMemberElm.addElement( " age " );

7.设置节点文字.

ageElm.setText( " 29 " );

8.删除某节点.

parentElm.remove(childElm); // childElm是待删除的节点,parentElm是其父节点

9.添加一个CDATA节点.

         Element contentElm = infoElm.addElement( " content " );
         contentElm.addCDATA(diary.getContent());

            contentElm.getText(); // 特别说明：获取节点的CDATA值与获取节点的值是一个方法
            contentElm.clearContent(); //清除节点中的内容，CDATA亦可

三.属性相关.
1.取得某节点下的某属性

             Element root = document.getRootElement();    
             Attribute attribute = root.attribute( " size " ); // 属性名name

2.取得属性的文字

             String text = attribute.getText();

也可以用:

String text2 = root.element( " name " ).attributeValue( " firstname " );

这个是取得根节点下name字节点的属性firstname的值.

3.遍历某节点的所有属性

  Element root = document.getRootElement();    
             for (Iterator it = root.attributeIterator();it.hasNext();) {
                 Attribute attribute  =  (Attribute) it.next();
                 String text = attribute.getText();
                 System.out.println(text);
             }

4.设置某节点的属性和文字.

newMemberElm.addAttribute( " name " , " sitinspring " );

5.设置属性的文字

             Attribute attribute = root.attribute( " name " );
             attribute.setText( " sitinspring " );

6.删除某属性

             Attribute attribute = root.attribute( " size " ); // 属性名name
             root.remove(attribute);

四.将文档写入XML文件.
1.文档中全为英文,不设置编码,直接写入的形式.

XMLWriter writer = new XMLWriter( new FileWriter( " output.xml " ));
writer.write(document);
writer.close();

2.文档中含有中文,设置编码格式写入的形式.

             OutputFormat format = OutputFormat.createPrettyPrint();
             format.setEncoding( " GBK " );     // 指定XML编码        
             XMLWriter writer = new XMLWriter( new FileWriter( " output.xml " ),format);
            
             writer.write(document);
             writer.close();

五.字符串与XML的转换
1.将字符串转化为XML

String text = " <members> <member>sitinspring</member> </members> " ;
Document document = DocumentHelper.parseText(text);

2.将文档或节点的XML转化为字符串.

             SAXReader reader = new SAXReader();
             Document   document = reader.read( new File( " input.xml " ));            
             Element root = document.getRootElement();                
             String docXmlText = document.asXML();
             String rootXmlText = root.asXML();
             Element memberElm = root.element( " member " );
             String memberXmlText = memberElm.asXML();