使用servlet产生随机验证码

来源：互联网发布：网络上说的cp什么意思编辑：程序博客网时间：2024/05/18 23:53

图片效果:

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.awt.*;
import java.awt.image.*;
import java.util.*;
import javax.imageio.*;
import com.sun.image.codec.jpeg.*;

public class ValidImage extends HttpServlet
{
private static final String CONTENT_TYPE = "image/jpeg; charset=GB2312";

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

//Process the HTTP Get request
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
response.setContentType(CONTENT_TYPE);
//设置页面不缓存

HttpSession session=request.getSession();

  response.setHeader("Pragma","No-cache");
  response.setHeader("Cache-Control","no-cache");
  response.setDateHeader("Expires", 0);
  // 在内存中创建图象
  int width=60, height=20;
  BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
  // 获取图形上下文
  Graphics g = image.getGraphics();
  // 设定背景色
  g.setColor(getRandColor(155,254));
  //g.setColor(new Color(255,255,255));
  g.fillRect(0, 0, width, height);
  //设定字体
  g.setFont(new Font("Times New Roman",Font.PLAIN,18));
  //画边框
  //g.setColor(new Color());
  //g.drawRect(0,0,width-1,height-1);
  // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
  g.setColor(getRandColor(160,220));

//生成随机类
Random random = new Random();

  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);
  }
  // 取随机产生的认证码(4位数字)
  String sRand="";
  for (int i=0;i<4;i++)
  {
   String rand=String.valueOf(random.nextInt(10));
   sRand+=rand;
   // 将认证码显示到图象中
   g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
   g.drawString(rand,13*i+6,16);
  }
  // 将认证码存入SESSION
  session.setAttribute("randcode",sRand);
  // 图象生效
  g.dispose();
  // 输出图象到页面
  ImageIO.write(image, "JPEG", response.getOutputStream());

}

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

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

这里产生了一个 randcode 的session, 用户在第二页验证此验证码