dom4j读写xml文件 -优快云博客

本文链接：https://blog.youkuaiyun.com/hailan321/article/details/83891163

本文介绍使用DOM4J库在Java中读写XML文件的方法。包括创建、读取、修改及删除XML节点与属性的具体步骤，并展示了如何利用XPath快速定位节点。

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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();
}
}