java servlet/jsp隨機驗證碼

package com.banding.web.util;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.servlet.ServletException;
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 Image extends HttpServlet {
 
 //public static final long serialVersionUID = 1L ;
 
    //private static final String CONTENT_TYPE = "text/html; charset=GBK";

    public Color getRandColor(int fc, int bc) { //給定範圍獲得隨機顏色
        Random random = new Random();
        if (fc > 255) {
            fc = 255;
        }
        if (bc > 255) {
            bc = 255;
        }
        int r = fc + random.nextInt(bc - fc);
        int g = fc + random.nextInt(bc - fc);
        int b = fc + random.nextInt(bc - fc);
        return new Color(r, g, b);
    }

    //Initialize global variables
    public void init() throws ServletException {
    }

    //Process the HTTP Get request
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws
            ServletException, IOException {
        //設定頁面不緩衝
        response.setHeader("Pragma", "No-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);

  // 在記憶體中建立圖象
        int width = 60, height = 20;
        BufferedImage image = new BufferedImage(width, height,
                                                BufferedImage.TYPE_INT_RGB);

  // 擷取圖形上下文
        Graphics g = image.getGraphics();

  //產生隨機類
        Random random = new Random();

  // 設定背景色
        g.setColor(getRandColor(200, 250));
        g.fillRect(0, 0, width, height);

  //設定字型
        g.setFont(new Font("Times New Roman", Font.PLAIN, 18));

  //畫邊框
  //g.setColor(new Color());
  //g.drawRect(0,0,width-1,height-1);

  // 隨機產生155條幹擾線，使圖象中的認證碼不易被其它程式探測到
        g.setColor(getRandColor(160, 200));
        for (int i = 0; i < 155; i++) {
            int x = random.nextInt(width);
            int y = random.nextInt(height);
            int xl = random.nextInt(12);
            int yl = random.nextInt(12);
            g.drawLine(x, y, x + xl, y + yl);
        }

  // 取隨機產生的認證碼(4位元字)
        String sRand = "";
        for (int i = 0; i < 4; i++) {
            String rand = String.valueOf(random.nextInt(10));
            sRand += rand;
  // 將認證碼顯示到圖象中
            g.setColor(new Color(20 + random.nextInt(110),
                                 20 + random.nextInt(110),
                                 20 + random.nextInt(110)));
  //調用函數出來的顏色相同，可能是因為種子太接近，所以只能直接產生
            g.drawString(rand, 13 * i + 6, 16);
        }

  // 將認證碼存入SESSION
        request.getSession().setAttribute("rand", sRand);

  // 圖象生效
        g.dispose();

  // 輸出圖象到頁面
  //ImageIO.write(image, "JPEG", response.getOutputStream());
        JPEGImageEncoder encode = JPEGCodec.createJPEGEncoder(response.
                getOutputStream());
        encode.encode(image);

    }

    //Clean up resources
    public void destroy() {
    }
}

 

上面的代碼可以直接用，在web.xml中配置好以後就可以在瀏覽器中訪問這個servlet，能得到下面的效果

若要在jsp頁面中使用這個驗證碼 只需用一個 <img src="那個servlet的地址" />

這樣就好了