DOM4J操作XML(包括封装和解析)

先来看看dom4j中相应XML的DOM树建立的继承关系

针对于XML标准定义。相应于图2-1列出的内容，dom4j提供了下面实现：

以下给出一个详细事例:
package com.iboxpay.settlement.gateway.common.util;

import java.io.IOException;
import java.io.StringReader;
import java.io.StringWriter;

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

import com.iboxpay.settlement.gateway.ccb.Constant;
import com.iboxpay.settlement.gateway.common.exception.PackMessageException;
import com.iboxpay.settlement.gateway.common.exception.ParseMessageException;

/**
* DOM4j工具类
* @author caolipeng
*/
public class DomUtil {
   /**
   * 加入孩子节点元素
   * @param parent 父节点
   * @param childName 孩子节点名称
   * @param childValue 孩子节点值
   * @return 新增节点
   */
   public static Element addChild(Element parent, String childName,
           String childValue) {
       Element child = parent.addElement(childName);//加入节点元素
       child.setText(childValue == null ?

"" : childValue); //为元素设值
       return child;
   }
   /**
   * DOM4j的Document对象转为XML报文串
   * @param document
   * @param charset
   * @return 经过解析后的xml字符串
   */
   public static String documentToString(Document document,String charset) {
       StringWriter stringWriter = new StringWriter();
        OutputFormat format = OutputFormat.createPrettyPrint();//获得格式化输出流
        format.setEncoding(charset);//设置字符集,默觉得UTF-8
       XMLWriter xmlWriter = new XMLWriter(stringWriter, format);//写文件流
       try {
           xmlWriter.write(document);
           xmlWriter.flush();
           xmlWriter.close();
       } catch (IOException e) {
           throw new RuntimeException(e);
       }
       return stringWriter.toString();
   }
   /**
   * 去掉声明头的(即<?xml...?>去掉)
   * @param document
   * @param charset
   * @return
   */
   public static String documentToStringNoDeclaredHeader(Document document,String charset) {
       String xml = documentToString(document, charset);
       return xml.replaceFirst("\s*<[^<>]+>\s*", "");
   }
   /**
   * 解析XML为Document对象
   * @param xml 被解析的XMl
   * @return Document
   * @throws ParseMessageException
   */
   public final static Element parseXml(String xml)throws ParseMessageException{
       StringReader sr = new StringReader(xml);
        SAXReader saxReader = new SAXReader();
        Document document;
       try {
           document = saxReader.read(sr);
       } catch (DocumentException e) {
           throw new ParseMessageException(e);
       }
        Element rootElement = document.getRootElement();
        return rootElement;
   }

   public final static String getText(Element e, String tag){
       Element _e = e.element(tag);
       if(_e != null)
           return _e.getText();
       else
           return null;
   }
   public final static String getTextTrim(Element e, String tag){
       Element _e = e.element(tag);
       if(_e != null)
           return _e.getTextTrim();
       else
           return null;
   }
   /**
   * 获取节点值.节点必须不能为空，否则抛错
   * @param parent
   * @param tag
   * @return
   * @throws ParseMessageException
   */
   public final static String getTextTrimNotNull(Element parent, String tag) throws ParseMessageException{
       Element e = parent.element(tag);
       if(e == null)
           throw new ParseMessageException(parent.getName() + " -> " + tag + " 节点为空.");
       else
           return e.getTextTrim();
   }
   /**
   * 节点必须不能为空，否则抛错
   * @param parent
   * @param tag
   * @return
   * @throws ParseMessageException
   */
   public final static Element elementNotNull(Element parent, String tag) throws ParseMessageException{
       Element e = parent.element(tag);
       if(e == null)
           throw new ParseMessageException(parent.getName() + " -> " + tag + " 节点为空.");
       else
           return e;
   }
   public static void main(String[] args) throws PackMessageException, ParseMessageException {
       Document document = DocumentHelper.createDocument();
       document.setXMLEncoding("GB2312");
       Element root = document.addElement("TX");
       DomUtil.addChild(root, "REQUEST_SN", "bankBatchSeqId");
       DomUtil.addChild(root, "CUST_ID", "cust_id");
       DomUtil.addChild(root, "USER_ID", "user_id");
       DomUtil.addChild(root, "PASSWORD", "password");
       DomUtil.addChild(root, "TX_CODE", "txCode");
       DomUtil.addChild(root, "LANGUAGE", "CN");
        Element tx_info = root.addElement(Constant.TX_INFO);
       DomUtil.addChild(tx_info, Constant.REQUEST_SN1, "request_sn1");
       String xml = DomUtil.documentToStringNoDeclaredHeader(root.getDocument(), "GBK");
       System.out.println(xml);
       root = parseXml(xml);
       System.out.println(root.element("TX_INFO").elementText("REQUEST_SN1"));
   }
}
主函数測试结果为:
<TX>
<REQUEST_SN>bankBatchSeqId</REQUEST_SN>
<CUST_ID>cust_id</CUST_ID>
<USER_ID>user_id</USER_ID>
<PASSWORD>password</PASSWORD>
<TX_CODE>txCode</TX_CODE>
<LANGUAGE>CN</LANGUAGE>
<TX_INFO>
    <REQUEST_SN1>request_sn1</REQUEST_SN1>
</TX_INFO>
</TX>

request_sn1

博客參考文献:http://www.cnblogs.com/macula/archive/2011/07/27/2118003.html