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(); 使用XPath快速找到节点.

读取的XML文档示例

 <? xml   version = "1.0"   encoding = "UTF-8" ?>
 < projectDescription >
    < name > MemberManagement </ name >
    < comment > </ comment >
    < projects >
      < project > PRJ1 </ project >
      < project > PRJ2 </ project >
      < project > PRJ3 </ project >
      < project > PRJ4 </ project >
    </ projects >
    < buildSpec >
      < buildCommand >
        < name > org.eclipse.jdt.core.javabuilder </ name >
        < arguments >
        </ arguments >
      </ buildCommand >
    </ buildSpec >
    < natures >
      < nature > org.eclipse.jdt.core.javanature </ nature >
    </ natures >
 </ projectDescription >

 
使用XPath快速找到节点project.

 public   static   void  main(String[] args){
    SAXReader reader =  new  SAXReader();

     try {
      Document  doc = reader.read( new  File( "sample.xml" ));

      List projects=doc.selectNodes( "/projectDescription/projects/project" );

      Iterator it=projects.iterator();

       while (it.hasNext()){
        Element elm=(Element)it.next();
        System.out.println(elm.getText());
      }

    }
     catch (Exception ex){
       ex.printStackTrace();
    }
  }