* XML（Extensible Markup Language，可擴充套件標記語言）

1、XML DOM解析：

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
File f = ...
Document doc=builder.parse(f);
URL u=...
Document doc=builder.parse(u);
InputStream in=...
Document doc=builder.parse(in);
 

2、XML DTD（Document Type Definition，文件型別驗證）驗證：

• XML中驗證：<!DOCTYPE configuration [<!Element configuration ...> more rules ...]>
• 外部dtd檔案驗證：<!DOCTYPE configuration SYSTEM "config.dtd">
• URL驗證：<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN" "http://java.sun.com/j2ee/dtds/web-app_2.2.dtd">

3、XML Schema：其本身就是一個XML檔案，同時其內容指明瞭某種XML的格式。

關於dtd和XML Schema文件的編寫可以參考《Java核心技術 卷II》Page 152-154中給出的具體檔案內容示例。

例項主要邏輯：

• HelloWorld.java提供反射機制訪問的類
• test.xml檔案給出HelloWorld類的資訊
• Test.java檔案讀取xml中的類資訊，並利用反射機制生成HelloWorld類的例項，並呼叫其中的方法

具體檔案如圖所示

各檔案內容如下

HelloWorld.java

import java.util.Arrays;

public class HelloWorld {

	public void sayHello(){
		System.out.println("sya hello");
	}
  
	public void sayHello(int i){
		System.out.println("sya hello: " + i);
	}

	public void sayHello(String[] str){
		System.out.println("say hello: " + Arrays.toString(str));
	}

	public static void main(String[] args) {
		String[] str = {"a", "b"};
		HelloWorld h = new HelloWorld();
		h.sayHello(str);
		System.out.println("hello world");
	}
}
 

test.xml

<?xml version="1.0" encoding="UTF-8"?>

<element>
	<import class="HelloWorld"/>
</element>

Test.java

import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.lang.reflect.Method;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

public class Test {
  /**
   * @param args
   * @throws IOException
   * @throws ParserConfigurationException 
   * @throws SAXException 
   * @throws ClassNotFoundException 
   * @input
   */
  public static void main(String[] args) throws Exception, ParserConfigurationException, SAXException, ClassNotFoundException {
    DocumentBuilder builder;
    builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
    if (args.length == 0)
      return;
    else {
      InputStream in=null;
      try {
		//讀取XML檔案
        String filePath = args[0];
        File file = new File(filePath);
        in = new FileInputStream(file);
        Document doc=builder.parse(in);
        Element eRoot = doc.getDocumentElement();
        NodeList nl = eRoot.getChildNodes();
        for (int i = 0; i < nl.getLength(); i++) {
          Node n = nl.item(i);
          if (!(n instanceof Element))
            continue;
          Element e = (Element) n;
          System.out.println("Element: " + e.getNodeName());
		  //取得類名
          String className=e.getAttribute("class");
          Class cl=Class.forName(className);
		  //建立類例項物件
          Object o=cl.newInstance();
		  //動態呼叫方法
          Method m=cl.getMethod("sayHello",  String[].class);
          Object[] ob=new Object[1];
          String arg[]=new String[1];
          arg[0]="1";
          ob[0]=arg;
          m.invoke(o,ob);
        }
      } 
	  finally {
        in.close();
      }
    }
  }
}

具體執行方法：

1. javac HelloWorld.java
2. javac -encoding utf-8 Test.java
3. java Test test.xml

輸出：

最後檔案：