Jdom使用指南（代码）
好了，书归正传，现在开始介绍jdom包的使用。
jdom包的结构包括：
org.jdom 包含了所有的xml文档要素的java类
org.jdom.adapters 包含了与dom适配的java类
org.jdom.filter 包含了xml文档的过滤器类
org.jdom.input 包含了读取xml文档的类
org.jdom.output 包含了写入xml文档的雷
org.jdom.transform 包含了将jdomxml文档接口转换为其他xml文档接口
org.jdom.xpath 包含了对xml文档xpath操作的类
下面将通过一个例子介绍jdom的常用操作
生成xml文档：
下面的类将生成一个xml文档：
/*
*Createdon2004-10-9
*
*写入xml文件的例子
*/
/**
*@authorlnman
*
*Tochangethetemplateforthisgeneratedtypecommentgoto
*Window>Preferences>Java>CodeGeneration>CodeandComments
*/
importjava.io.*;
importorg.jdom.*;
importorg.jdom.output.*;
publicclassWriteXML
{
publicvoidBuildXML()throwsException
{
Elementroot,student,number,name,age;
root=newElement("student-info");//生成根元素：student-info
student=newElement("student"); //生成元素：student,该元素中将包含元素number,name,age
number=newElement("number");
name=newElement("name");
age=newElement("age");
Documentdoc=newDocument(root); //将根元素植入文档doc中
number.setText("001");
name.setText("lnman");
age.setText("24");
student.addContent(number);
student.addContent(name);
student.addContent(age);
root.addContent(student);
Formatformat=Format.getCompactFormat();
format.setEncoding("gb2312"); //设置xml文件的字符为gb2312
format.setIndent(" "); //设置xml文件的缩进为4个空格
XMLOutputterXMLOut=newXMLOutputter(format);//在元素后换行，每一层元素缩排四格
XMLOut.output(doc,newFileOutputStream("studentinfo.xml"));
}
publicstaticvoidmain(String[]args)throwsException
{
WriteXMLw=newWriteXML();
System.out.println("NowwebuildanXMLdocument.....");
w.BuildXML();
System.out.println("finished!");
}
}
生成的xml文档为：
<?xmlversion="1.0"encoding="gb2312"?>
<student-info>
<student>
<number>001</number>
<name>lnman</name>
<age>24</age>
</student>
</student-info>
读取xml文档的例子：
/*
*Createdon2004-10-9
*
*用jdom读取xml文档的例子
*
*/
/**
*@authorlnman
*
*Tochangethetemplateforthisgeneratedtypecommentgoto
*Window>Preferences>Java>CodeGeneration>CodeandComments
*/
importorg.jdom.output.*;
importorg.jdom.input.*;
importorg.jdom.*;
importjava.io.*;
importjava.util.*;
publicclassReadXML
{
publicstaticvoidmain(String[]args)throwsException
{
SAXBuilderbuilder=newSAXBuilder();
Documentread_doc=builder.build("studentinfo.xml");
Elementstu=read_doc.getRootElement();
Listlist=stu.getChildren("student");
for(inti=0;i<list.size();i++)
{
Elemente=(Element)list.get(i);
Stringstr_number=e.getChildText("number");
Stringstr_name=e.getChildText("name");
Stringstr_age=e.getChildText("age");
System.out.println("---------STUDENT--------------");
System.out.println("NUMBER:"+str_number);
System.out.println("NAME:"+str_name);
System.out.println("AGE:"+str_age);
System.out.println("------------------------------");
System.out.println();
}
}
}
Xpath例子：
JDOM的关于XPATH的api在org.jdom.xpath这个包里。这个包下，有一个抽象类XPath.java和实现类JaxenXPath.java， 使用时先用XPath类的静态方法newInstance(String xpath)得到XPath对象，然后调用它的selectNodes(Object context)方法或selectSingleNode(Object context)方法，前者根据xpath语句返回一组节点(List对象)；后者根据一个xpath语句返回符合条件的第一个节点(Object类型)。请看jdom-1.0自带的范例程序：
它分析在web.xml文件中的注册的servlet的个数及参数个数，并输出角色名。
web.xml文件：
<?xml version="1.0" encoding="ISO-8859-1"?>
<!--
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN"
"http://java.sun.com/j2ee/dtds/web-app_2.2.dtd">
-->
<web-app>
<servlet>
<servlet-name>snoop</servlet-name>
<servlet-class>SnoopServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>file </servlet-name>
<servlet-class>ViewFile</servlet-class>
<init-param>
<param-name>initial</param-name>
<param-value>1000</param-value>
<description>The initial value for the counter <!-- optional --></description>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>mv</servlet-name>
<url-pattern>*.wm</url-pattern>
</servlet-mapping>
<distributed/>
<security-role>
<role-name>manager</role-name>
<role-name>director</role-name>
<role-name>president</role-name>
</security-role>
</web-app>
处理程序：
import java.io.*;
import java.util.*;
import org.jdom.*;
import org.jdom.input.*;
import org.jdom.output.*;
import org.jdom.xpath.*;
/**
* <p><code>XPathReader</code> demonstrates how to
* read a Servlet 2.2 Web Archive file using XPath.
* </p>
*
* @author Jason Hunter
* @version 1.0
*/
public class XPathReader {
public static void main(String[] args) throws IOException, JDOMException {
if (args.length != 1) {
System.err.println("Usage: java XPathReader web.xml");
return;
}
String filename = args[0];//从命令行输入web.xml
PrintStream out = System.out;
SAXBuilder builder = new SAXBuilder();
Document doc = builder.build(new File(filename));//得到Document对象
// Print servlet information
XPath servletPath = XPath.newInstance("//servlet");//,选择任意路径下servlet元素
List servlets = servletPath.selectNodes(doc);//返回所有的servlet元素。
out.println("This WAR has "+ servlets.size() +" registered servlets:");
Iterator i = servlets.iterator();
while (i.hasNext()) {//输出servlet信息
Element servlet = (Element) i.next();
out.print("\t" + servlet.getChild("servlet-name")
.getTextTrim() +
" for " + servlet.getChild("servlet-class")
.getTextTrim());
List initParams = servlet.getChildren("init-param");
out.println(" (it has " + initParams.size() + " init params)");
}
// Print security role information
XPath rolePath = XPath.newInstance("//security-role/role-name/text()");
List roleNames = rolePath.selectNodes(doc);//得到所有的角色名
if (roleNames.size() == 0) {
out.println("This WAR contains no roles");
} else {
out.println("This WAR contains " + roleNames.size() + " roles:");
i = roleNames.iterator();
while (i.hasNext()) {//输出角色名
out.println("\t" + ((Text)i.next()).getTextTrim());
}
}
}
}
输出结果:
C:\java>java XPathReader web.xml
This WAR has 2 registered servlets:
snoop for SnoopServlet (it has 0 init params)
file for ViewFile (it has 1 init params)
This WAR contains 3 roles:
manager
director
president
