jdom 简介.txt

JODM是一个开源的项目.它基于树性结构

<?xml version="1.0" encoding="gb2312"?>

<student-info>

    <student>

        <number>001</number>

        <name>lnman</name>

        <age>24</age>

    </student>

</student-info>

 

 

创建XML文档2：

 public class CreateXML {

  public void Create() {

   try {

    Document doc = new Document();   

    ProcessingInstruction pi=new ProcessingInstruction("xml-stylesheet","type="text/xsl" href="test.xsl"");

    doc.addContent(pi);    

    Namespace ns = Namespace.getNamespace("http://www.bromon.org" );

    Namespace ns2 = Namespace.getNamespace("other", "http://www.w3c.org" );

    Element root = new Element("根元素", ns);

    root.addNamespaceDeclaration(ns2);

    doc.setRootElement(root);

    Element el1 = new Element("元素一");

    el1.setAttribute("属性", "属性一");    

    Text text1=new Text("元素值");

             Element em = new Element("元素二").addContent("第二个元素");

    el1.addContent(text1);

             el1.addContent(em);             

             Element el2 = new Element("元素三").addContent("第三个元素");

             root.addContent(el1);

             root.addContent(el2);             

             //缩进四个空格,自动换行,gb2312编码

             XMLOutputter outputter = new XMLOutputter("  ", true,"GB2312");

             outputter.output(doc, new FileWriter("test.xml"));

         }catch(Exception e)  {

          System.out.println(e);

         }

     }     

     public static void main(String args[]) {

      new CreateXML().Create();

     }     

 }

2、读取xml文档的例子：

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();

        }  

       }

}

3、DTD验证的：

 public class XMLWithDTD {

  public void validate()  {

   try {

    SAXBuilder builder = new SAXBuilder(true);

    builder.setFeature("http://xml.org/sax/features/validation";,true); 

    Document doc = builder.build(new FileReader("author.xml"));    

    System.out.println("搞掂");

    XMLOutputter outputter = new XMLOutputter();

    outputter.output(doc, System.out);

   }catch(Exception e) {

    System.out.println(e);

   }   

  }

  public static void main(String args[]) {

   new XMLWithDTD().validate();

  }  

 }

 　　需要说明的是，这个程序没有指明使用哪个DTD文件。DTD文件的位置是在XML中指定的，而且DTD不支持命名空间，一个XML只能引用一个DTD，所以程序直接读取XML中指定的DTD，程序本身不用指定。不过这样一来，好象就只能使用外部式的DTD引用方式了？高人指点。

 

 

4、XML Schema验证的：

 public class XMLWithSchema {

  String xml="test.xml";

  String schema="test-schema.xml";

  public void validate() {

   try {

    SAXBuilder builder = new SAXBuilder(true);

    //指定约束方式为XML schema

    builder.setFeature("http://apache.org/xml/features/validation/schema";,  true);

    //导入schema文件

builder.setProperty("http://apache.org/xml/properties/schema/external-noNamespaceSchemaLocation";,schema); 

    Document doc = builder.build(new FileReader(xml));    

    System.out.println("搞掂");

    XMLOutputter outputter = new XMLOutputter();

    outputter.output(doc, System.out);

   }catch(Exception e) {

    System.out.println("验证失败:"+e);

   }  

  } 

 }

 上面的程序就指出了要引入的XML Schema文件的位置。

 

 

 系统默认输出是UTF-8，这有可能导致出现乱码。

5、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.*;  

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

 

 

6、数据输入要用到XML文档要通过org.jdom.input包，反过来需要org.jdom.output。如前面所说，关是看API文档就能够使用。 

我们的例子读入XML文件exampleA.xml，加入一条处理指令，修改第一本书的价格和作者，并添加一条属性，然后写入文件exampleB.xml： 

//exampleA.xml 

<?xml version="1.0" encoding="GBK"?> 

<bookList> 

<book> 

<name>Java编程入门</name> 

<author>张三</author> 

<publishDate>2002-6-6</publishDate> 

<price>35.0</price> 

</book> 

<book> 

<name>XML在Java中的应用</name> 

<author>李四</author> 

<publishDate>2002-9-16</publishDate> 

<price>92.0</price> 

</book> 

</bookList> 

//testJDOM.java 

import org.jdom.*; 

import org.jdom.output.*; 

import org.jdom.input.*; 

import java.io.*; 

public class TestJDOM{ 

public static void main(String args[])throws Exception{ 

SAXBuilder sb = new SAXBuilder(); 

//从文件构造一个Document，因为XML文件中已经指定了编码，所以这里不必了 

Document doc = sb.build(new FileInputStream("exampleA.xml")); 

ProcessingInstruction pi = new ProcessingInstruction//加入一条处理指令 

("xml-stylesheet","href=\"bookList.html.xsl\" type=\"text/xsl\""); 

doc.addContent(pi); 

Element root = doc.getRootElement(); //得到根元素 

java.util.List books = root.getChildren(); //得到根元素所有子元素的集合 

Element book = (Element)books.get(0); //得到第一个book元素 

//为第一本书添加一条属性 

Attribute a = new Attribute("hot","true"); 

book.setAttribute(a); 

Element author = book.getChild("author"); //得到指定的字元素 

author.setText("王五"); //将作者改为王五 

//或 Text t = new Text("王五");book.addContent(t); 

Element price = book.getChild("price"); //得到指定的字元素 

//修改价格，比较郁闷的是我们必须自己转换数据类型，而这正是JAXB的优势 

author.setText(Float.toString(50.0f)); 

String indent = " "; 

boolean newLines = true; 

XMLOutputter outp = new XMLOutputter(indent,newLines,"GBK"); 

outp.output(doc, new FileOutputStream("exampleB.xml")); 

} 

}; 

执行结果exampleB.xml： 

<?xml version="1.0" encoding="GBK"?> 

<bookList> 

<book hot=”true”> 

<name>Java编程入门</name> 

<author>50.0</author> 

<publishDate>2002-6-6</publishDate> 

<price>35.0</price> 

</book> 

<book> 

<name>XML在Java中的应用</name> 

<author>李四</author> 

<publishDate>2002-9-16</publishDate> 

<price>92.0</price> 

</book> 

</bookList> 

<?xml-stylesheet href="bookList.html.xsl" type="text/xsl"?> 

在默认情况下，JDOM的Element类的getText()这类的方法不会过滤空白字符，如果你需要过滤，用setTextTrim() 。