项目结构如下，MyEclipse中新建一个Web Project，取名servlet

 

1、src下new一个servlet类

 

package com.servlet;import java.awt.Color;import java.awt.Font;import java.awt.Graphics2D;import java.awt.image.BufferedImage;import java.io.IOException;import java.io.PrintWriter;import java.util.Random;import javax.servlet.ServletException;import javax.servlet.ServletOutputStream;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.sun.image.codec.jpeg.JPEGCodec;import com.sun.image.codec.jpeg.JPEGImageEncoder;public class IdentityServlet extends HttpServlet {    public static final char[] chars={
   '2','3','4','5','6','7','8','9','A'};//自定义验证码池    public static Random random=new Random();　　//随机数        public static String getRandomString(){　　//获取6位随机数，放在图片里        StringBuffer buffer=new StringBuffer();        for(int i=0;i<6;i++){            buffer.append(chars[random.nextInt(chars.length)]);        }        return buffer.toString();    }        public static Color getRandomColor(){　　//获取随机的颜色        return new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255));    }        public static Color getReverseColor(Color c){　　//返回某颜色的反色        return new Color(255 - c.getRed(), 255 - c.getGreen(), 255 - c.getBlue());    }        /**     * Constructor of the object.     */    public IdentityServlet() {        super();    }    /**     * Destruction of the servlet. 
     */    public void destroy() {        super.destroy(); // Just puts "destroy" string in log        // Put your code here    }    /**     * The doGet method of the servlet. 
     *     * This method is called when a form has its tag value method equals to get.     *      * @param request the request send by the client to the server     * @param response the response send by the server to the client     * @throws ServletException if an error occurred     * @throws IOException if an error occurred     */    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        response.setContentType("image/jpeg");　　//设置输出类型                String randomString = getRandomString();　　//随机字符串        request.getSession(true).setAttribute("randomString", randomString);//放到session里                int width=100;　　//图片宽度        int height=30;　　//图片高度                Color color=getRandomColor();　　//随机颜色，用于背景色        Color reverse=getReverseColor(color);//反色，用于前景色        //创建一个彩色图片        BufferedImage bi=new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);        Graphics2D g=bi.createGraphics();　　//绘图对象        g.setFont(new Font(Font.SANS_SERIF,Font.BOLD,16));//设置字体        g.setColor(color);//设置颜色        g.fillRect(0, 0, width, height);//绘制背景        g.setColor(reverse);        g.drawString(randomString, 18, 20);//绘制随机字符        for(int i=0,n=random.nextInt(100);i
     

* * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } /** * Initialization of the servlet.

* * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here }}