Java操作XML文件 dom4j

在项目中，我们很多都用到了xml文件，无论是参数配置还是与其它系统的数据交互。
今天就来讲一下Java 中使用dom4j来操作XML文件。

我们需要引入的包：

//文件包
import?java.io.ByteArrayOutputStream;
import?java.io.File;
import?java.io.FileWriter;
//工具包
import?java.util.Iterator;
import?java.util.List;
//dom4j包
import?org.dom4j.Attribute;
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;

1、将XML文件的内容转化为String

???/**
????*?doc2String
????*?将xml文档内容转为String
????*?@return?字符串
????*?@param?document
????*/
???public?static?String?doc2String(Document?document)
???{
??????String?s?=?"";
??????try
??????{
???????????//使用输出流来进行转化
???????????ByteArrayOutputStream?out?=?new?ByteArrayOutputStream();
???????????//使用GB2312编码
???????????OutputFormat?format?=?new?OutputFormat("??",?true,?"GB2312");
???????????XMLWriter?writer?=?new?XMLWriter(out,?format);
???????????writer.write(document);
???????????s?=?out.toString("GB2312");
??????}catch(Exception?ex)
??????{????????????
???????????ex.printStackTrace();
??????}??????
??????return?s;
???}

2、将符合XML格式的String 转化为XML Document

???/**
????*?string2Document
????*?将字符串转为Document
????*?@return?
????*?@param?s?xml格式的字符串
????*/
???public?static?Document?string2Document(String?s)
???{
??????Document?doc?=?null;
??????try
??????{
???????????doc?=?DocumentHelper.parseText(s);
??????}catch(Exception?ex)
??????{????????????
???????????ex.printStackTrace();
??????}
??????return?doc;
???}

3、将Document对象保存为一个xml文件到本地

???/**
????*?doc2XmlFile
????*?将Document对象保存为一个xml文件到本地
????*?@return?true:保存成功??flase:失败
????*?@param?filename?保存的文件名
????*?@param?document?需要保存的document对象
????*/
???public?static?boolean?doc2XmlFile(Document?document,String?filename)
???{
??????boolean?flag?=?true;
??????try
??????{
????????????/*?将document中的内容写入文件中?*/
????????????//默认为UTF-8格式，指定为"GB2312"
????????????OutputFormat?format?=?OutputFormat.createPrettyPrint();
????????????format.setEncoding("GB2312");
????????????XMLWriter?writer?=?new?XMLWriter(new?FileWriter(new?File(filename)),format);
????????????writer.write(document);
????????????writer.close();????????????
????????}catch(Exception?ex)
????????{
????????????flag?=?false;
????????????ex.printStackTrace();
????????}
????????return?flag;??????
???}

4、将xml格式的字符串保存为本地文件，如果字符串格式不符合xml规则，则返回失败

???/**
????*?string2XmlFile
????*?将xml格式的字符串保存为本地文件，如果字符串格式不符合xml规则，则返回失败
????*?@return?true:保存成功??flase:失败
????*?@param?filename?保存的文件名
????*?@param?str?需要保存的字符串
????*/
???public?static?boolean?string2XmlFile(String?str,String?filename)
???{
??????boolean?flag?=?true;
??????try
??????{
?????????Document?doc?=??DocumentHelper.parseText(str);???????
?????????flag?=?doc2XmlFile(doc,filename);
??????}catch?(Exception?ex)
??????{
?????????flag?=?false;
?????????ex.printStackTrace();
??????}
??????return?flag;
???}

5、载入一个xml文档

???/**
????*?load
????*?载入一个xml文档
????*?@return?成功返回Document对象，失败返回null
????*?@param?uri?文件路径
????*/
???public?static?Document?load(String?filename)
???{
??????Document?document?=?null;
??????try?
??????{?
??????????SAXReader?saxReader?=?new?SAXReader();
??????????document?=?saxReader.read(new?File(filename));
??????}
??????catch?(Exception?ex){
??????????ex.printStackTrace();
??????}??
??????return?document;
???}

?6、演示String保存为xml文件

???/**
????*?xmlWriteDemoByString
????*?演示String保存为xml文件
????*/
???public?void?xmlWriteDemoByString()
???{
??????String?s?=?"";
??????/**?xml格式标题?"<?xml?version='1.0'?encoding='GB2312'?>"?可以不用写*/
??????s?=?"<config>\r\n"
?????????+"???<ftp?name='DongDian'>\r\n"
?????????+"?????<ftp-host>127.0.0.1</ftp-host>\r\n"
?????????+"?????<ftp-port>21</ftp-port>\r\n"
?????????+"?????<ftp-user>cxl</ftp-user>\r\n"
?????????+"?????<ftp-pwd>longshine</ftp-pwd>\r\n"
?????????+"?????<!--?ftp最多尝试连接次数?-->\r\n"
?????????+"?????<ftp-try>50</ftp-try>\r\n"
?????????+"?????<!--?ftp尝试连接延迟时间?-->\r\n"
?????????+"?????<ftp-delay>10</ftp-delay>\r\n"
?????????+"??</ftp>\r\n"
?????????+"</config>\r\n";
??????//将文件生成到classes文件夹所在的目录里???
??????string2XmlFile(s,"xmlWriteDemoByString.xml");???
??????//将文件生成到classes文件夹里???
??????string2XmlFile(s,"classes/xmlWriteDemoByString.xml");??
???}

7、演示手动创建一个Document，并保存为XML文件

???/**
????*?演示手动创建一个Document，并保存为XML文件
????*/
???public?void?xmlWriteDemoByDocument()
???{
????????/**?建立document对象?*/
????????Document?document?=?DocumentHelper.createDocument();
????????/**?建立config根节点?*/
????????Element?configElement?=?document.addElement("config");
????????/**?建立ftp节点?*/
????????configElement.addComment("东电ftp配置");
????????Element?ftpElement?=?configElement.addElement("ftp");
????????ftpElement.addAttribute("name","DongDian");
????????/**?ftp?属性配置?*/
????????Element?hostElement?=?ftpElement.addElement("ftp-host");
????????hostElement.setText("127.0.0.1");
????????(ftpElement.addElement("ftp-port")).setText("21");
????????(ftpElement.addElement("ftp-user")).setText("cxl");
????????(ftpElement.addElement("ftp-pwd")).setText("longshine");
????????ftpElement.addComment("ftp最多尝试连接次数");
????????(ftpElement.addElement("ftp-try")).setText("50");
????????ftpElement.addComment("ftp尝试连接延迟时间");
????????(ftpElement.addElement("ftp-delay")).setText("10");????
????????/**?保存Document?*/
????????doc2XmlFile(document,"classes/xmlWriteDemoByDocument.xml");
???}

8、演示读取文件的具体某个节点的值

???/**
????*??演示读取文件的具体某个节点的值?
????*/
???public?static?void?xmlReadDemo()
???{
??????Document?doc?=?load("classes/xmlWriteDemoByDocument.xml");
??????//Element?root?=?doc.getRootElement();
??????/**?先用xpath查找所有ftp节点?并输出它的name属性值*/
??????List?list?=?doc.selectNodes("/config/ftp"?);
??????Iterator?it?=?list.iterator();
??????while(it.hasNext())
??????{???
??????????Element?ftpElement?=?(Element)it.next();
??????????System.out.println("ftp_name="+ftpElement.attribute("name").getValue());
??????}
??????/**?直接用属性path取得name值?*/
??????list?=?doc.selectNodes("/config/ftp/@name"?);
??????it?=?list.iterator();
??????while(it.hasNext())
??????{???
??????????Attribute?attribute?=?(Attribute)it.next();
??????????System.out.println("@name="+attribute.getValue());
??????}
??????/**?直接取得DongDian?ftp的?ftp-host?的值?*/
??????list?=?doc.selectNodes("/config/ftp/ftp-host"?);
??????it?=?list.iterator();
??????Element?hostElement=(Element)it.next();
??????System.out.println("DongDian's?ftp_host="+hostElement.getText());
???}

9、修改或删除某个值或属性

/**?ftp节点删除ftp-host节点?*/
ftpElement.remove(hostElement);?
/**?ftp节点删除name属性?*/
ftpElement.remove(nameAttribute);
/**?修改ftp-host的值?*/
hostElement.setText("192.168.0.1");?
/**?修改ftp节点name属性的值?*/
nameAttribute.setValue("ChiFeng");