對xml文檔的解析java中有很多種方法，例如使用dom、sax、jdom等等，相比之下，我覺得還是jdom比較方便。下面介紹一下jdom的基本使用方法，不對之處還請各位網(wǎng)友之交。謝謝！
最新的jdom可以到他的網(wǎng)站：http://www.jdom.org去下載，現(xiàn)在的版本是1.0版，下載之后將得到jdom-1.0.zip文件，解壓后進(jìn)入build文件夾將看到一個名為jdom.jar的包，這個就是jdom的類包了，將它加到你的classpath里就可以使用jdom提供的各種處理xml的類和他們的方法了。應(yīng)該注意的是在解壓后的文件夾里還有一個lib文件夾，里面保存的是使用jdom的環(huán)境包，不過我在我的jdk1.4下使用沒引用這些包一樣好用，不知道是jdk1.4中已經(jīng)包含了這些東西還是原來我的eclipse已經(jīng)引用了這些包，呵呵。
好了，書歸正傳，現(xiàn)在開始介紹jdom包的使用。
jdom包的結(jié)構(gòu)包括：
org.jdom 包含了所有的xml文檔要素的java類
org.jdom.adapters 包含了與dom適配的java類
org.jdom.filter 包含了xml文檔的過濾器類
org.jdom.input 包含了讀取xml文檔的類
org.jdom.output 包含了寫入xml文檔的雷
org.jdom.transform 包含了將jdom xml文檔接口轉(zhuǎn)換為其他xml文檔接口
org.jdom.xpath 包含了對xml文檔xpath操作的類
下面將通過一個例子介紹jdom的常用操作
生成xml文檔：
下面的類將生成一個xml文檔：
/*
* Created on 2004-10-9
*
* 寫入xml文件的例子
*/
/**
* @author lnman
*
* To change the template for this generated type comment go to
* Window>Preferences>Java>Code Generation>Code and Comments
*/
import java.io.*;
import org.jdom.*;
import org.jdom.output.*;
public class WriteXML
{
public void BuildXML() throws Exception
{
Element root,student,number,name,age;
root = new Element("student-info"); //生成根元素：student-info
student = new Element("student"); //生成元素：student,該元素中將包含元素number,name,age
number = new Element("number");
name = new Element("name");
age = new Element("age");
Document doc = new Document(root); //將根元素植入文檔doc中
number.setText("001");
name.setText("lnman");
age.setText("24");
student.addContent(number);
student.addContent(name);
student.addContent(age);
root.addContent(student);
Format format = Format.getCompactFormat();
format.setEncoding("gb2312"); //設(shè)置xml文件的字符為gb2312
format.setIndent(" "); //設(shè)置xml文件的縮進(jìn)為4個空格
XMLOutputter XMLOut = new XMLOutputter(format);//在元素后換行，每一層元素縮排四格
XMLOut.output(doc, new FileOutputStream("studentinfo.xml"));
}
public static void main(String[] args) throws Exception
{
WriteXML w = new WriteXML();
System.out.println("Now we build an XML document .....");
w.BuildXML();
System.out.println("finished!");
}
}
生成的xml文檔為：
<?xml version="1.0" encoding="gb2312"?>
<student-info>
<student>
<number>001</number>
<name>lnman</name>
<age>24</age>
</student>
</student-info>
讀取xml文檔的例子：
/*
* Created on 2004-10-9
*
*用jdom讀取xml文檔的例子
*
*/
/**
* @author lnman
*
* To change the template for this generated type comment go to
* Window>Preferences>Java>Code Generation>Code and Comments
*/
import org.jdom.output.*;
import org.jdom.input.*;
import org.jdom.*;
import java.io.*;
import java.util.*;
public class ReadXML
{
public static void main(String[] args) throws Exception
{
SAXBuilder builder = new SAXBuilder();
Document read_doc = builder.build("studentinfo.xml");
Element stu = read_doc.getRootElement();
List list = stu.getChildren("student");
for(int i = 0;i < list.size();i++)
{
Element e = (Element)list.get(i);
String str_number = e.getChildText("number");
String str_name = e.getChildText("name");
String str_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的關(guān)于XPATH的api在org.jdom.xpath這個包里。這個包下，有一個抽象類XPath.java和實(shí)現(xiàn)類JaxenXPath.java， 使用時先用XPath類的靜態(tài)方法newInstance(String xpath)得到XPath對象，然后調(diào)用它的selectNodes(Object context)方法或selectSingleNode(Object context)方法，前者根據(jù)xpath語句返回一組節(jié)點(diǎn)(List對象)；后者根據(jù)一個xpath語句返回符合條件的第一個節(jié)點(diǎn)(Object類型)。請看jdom-1.0自帶的范例程序：
它分析在web.xml文件中的注冊的servlet的個數(shù)及參數(shù)個數(shù)，并輸出角色名。
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>
處理程序：
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];//從命令行輸入web.xml
PrintStream out = System.out;
SAXBuilder builder = new SAXBuilder();
Document doc = builder.build(new File(filename));//得到Document對象
// Print servlet information
XPath servletPath = XPath.newInstance("http://servlet");//,選擇任意路徑下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()) {//輸出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("http://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()) {//輸出角色名
out.println(""t" + ((Text)i.next()).getTextTrim());
}
}
}
}
輸出結(jié)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
posted on 2007-11-20 17:04
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