//ImageServlet
package?com.muke;
import?java.awt.Color;
import?java.awt.Graphics;
import?java.awt.image.BufferedImage;
import?java.io.IOException;
import?java.util.Random;

import?javax.imageio.ImageIO;
import?javax.servlet.http.HttpServlet;
import?javax.servlet.http.HttpServletRequest;
import?javax.servlet.http.HttpServletResponse;

public?class?ImageServlet??extends?HttpServlet{

	public?void?doGet(HttpServletRequest?request,HttpServletResponse?response)?throws?IOException{
		
		BufferedImage?bi=?new?BufferedImage(68,22,BufferedImage.TYPE_INT_RGB);
	????Graphics?g=bi.getGraphics();
	????Color?c?=?new?Color(200,150,255);
	????g.setColor(c);
	????g.fillRect(0,?0,?68,?22);
	????
	????//驗證碼里面內容字母數字組合
	????char[]?ch?="ABCDEFGHIGKLMNOPQRSTUVWXYZ0123456789".toCharArray();
		Random?r?=new?Random();
		int?len=ch.length,index;
		StringBuffer?sb=new?StringBuffer();
		for(int?i=0;i<4;i++){
??????????index=r.nextInt(len);
????????g.setColor(new?Color(r.nextInt(88),r.nextInt(188),r.nextInt(255)));??//隨機產生顏色
		g.drawString(ch[index]+"",?(i*15)+3,?18);
		sb.append(ch[index]);
		}
		request.getSession().setAttribute("piccde",?sb.toString());
		ImageIO.write(bi,"JPG",response.getOutputStream());
	}
}

//web.xml
<?xml?version="1.0"?encoding="UTF-8"?>
<web-app?version="2.5"?
	xmlns="http://java.sun.com/xml/ns/javaee"?
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"?
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee?
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
	
	<servlet>
	??????<servlet-name>ImageServlet</servlet-name>
	??????<servlet-class>com.muke.ImageServlet</servlet-class>
	</servlet>
	<servlet-mapping>
	????????<servlet-name>ImageServlet</servlet-name>
	????????<url-pattern>/servlet/ImageServlet</url-pattern>
	</servlet-mapping>
??<welcome-file-list>
????<welcome-file>index.jsp</welcome-file>
??</welcome-file-list>
</web-app>