imageservlet.java

五种不同功能的jsp验证码提供下载

package web;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import com.sun.image.codec.jpeg.*;
import java.awt.*;
import com.sun.image.codec.jpeg.*;
import java.awt.image.BufferedImage;
import java.awt.image.DataBuffer;
import java.awt.geom.GeneralPath;
import javax.swing.*;
import java.math.*;
import javax.imageio.ImageIO;


public class ImageServlet extends HttpServlet {
    private static final String CONTENT_TYPE = "text/html; charset=GBK";

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

    //Process the HTTP Get request
    public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
   // 设置页面不缓存
   response.setHeader("Pragma", "No-cache");
   response.setHeader("Cache-Control", "no-cache");
   response.setDateHeader("Expires", 0);

   // 设置图片的长宽
   int width = 62, height = 22;

   // 创建内存图像
   BufferedImage image = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);
   
   // 获取图形上下文
   Graphics g = image.createGraphics();

   // 设定图像背景色(因为是做背景，所以偏淡)
   g.setColor(getRandColor(180, 250));
   g.fillRect(0, 0, width, height);
   
   // 设置字体
   g.setFont(new Font("Times New Roman", Font.PLAIN, 17));

   // 设置默认生成4个验证码
   int length = 4;
   java.util.Random rand = new Random(); // 设置随机种子

   /*
    * if (request.getParameter("length") != null) { try { length =
    * Integer.parseInt(request.getParameter("length")); }catch
    * (NumberFormatException e) {} }
    */
    
   // 设置备选验证码:包括"a-z"和数字"0-9"
   String base = "abcdefghijklmnopqrstuvwxyz0123456789";
   int size = base.length();
   StringBuffer str = new StringBuffer();
   for (int i = 0; i < length; i++) {
		int start = rand.nextInt(size);
    String tmpStr = base.substring(start, start + 1);

    str.append(tmpStr);
    
    // 生成随机颜色(因为是做前景，所以偏深)
    g.setColor(getRandColor(10, 150));

    // 将此字画到图片上
    // g.drawString(str.toString(), 4, 17);
    g.drawString(tmpStr, 13 * i + 6 + rand.nextInt(5), 14 + rand.nextInt(6));

   }

   // 将认证码存入session
   request.getSession().setAttribute("valiCode", str.toString());

   // 图象生效
   g.dispose();

   // 输出图象到页面
   ImageIO.write(image, "JPEG", response.getOutputStream());
   
  }




    //Process the HTTP Post request
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws
            ServletException, IOException {
        doGet(request, response);
    }

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

    // 给定范围获得一个随机颜色
Color getRandColor(int fc, int bc) {
 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);
}


}