验证码实现

关键字：验证码的实现



servlet代码：



package com.sinosoft.edu.common;

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

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
* 验证码 生成
* @author linzhen
*
*/
public class ValidateCodeServlet extends HttpServlet {

private static int WIDTH = 66;  
    private static int HEIGHT = 20;  
    private static int LENGTH = 4;  

protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {

this.doPost(req, resp);
}


protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

HttpSession session = request.getSession();  
 
         response.setContentType("image/jpeg");  
 
         ServletOutputStream sos = response.getOutputStream();  
 
         //设置浏览器不要缓存此图片  
         response.setHeader("Pragma","No-cache");  
         response.setHeader("Cache-Control","no-cache");  
         response.setDateHeader("Expires", 0);  
 
         //创建内存图象并获得其图形上下文  
         BufferedImage image =   
                new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);   
 
         Graphics g = image.getGraphics();  
 
         //产生随机的认证码  
         char [] rands = generateCheckCode();  
 
         //产生图像  
         drawBackground(g);  
 
         drawRands(g,rands);  
 
         //结束图像的绘制过程，完成图像  
         g.dispose();  
 
         //将图像输出到客户端  
         ByteArrayOutputStream bos = new ByteArrayOutputStream();  
 
         ImageIO.write(image, "JPEG", bos);  
 
         byte [] buf = bos.toByteArray();  
 
         response.setContentLength(buf.length);  
 
         //下面的语句也可写成：bos.writeTo(sos);  
         sos.write(buf);  
         bos.close();  
         sos.close();  
//System.out.print("*validateCodeservlei");
         //将当前验证码存入到Session或者数据库中,下一个表单处理中验证客户端提交的验证码是否正确  
         session.setAttribute("check_code",new String(rands));  
}

private static char [] generateCheckCode()  
    {  
       //定义验证码的字符表  
       String chars = "23456789ABCDEFGHKMNPQRSTUVWXYZ";  
 
       char [] rands = new char[LENGTH];  
       for(int i=0; i<LENGTH; i++)  
 
       {  
          int rand = (int)(Math.random() * 30);  
          rands[i] = chars.charAt(rand);  
       }  
 
       return rands;  
    }  

private void drawRands(Graphics g , char [] rands)   
    {  
       g.setColor(Color.BLACK);  
       g.setFont(new Font(null,Font.ITALIC|Font.BOLD,18));  

       //在不同的高度上输出验证码的每个字符           
       g.drawString("" + rands[0],1,17);  
       g.drawString("" + rands[1],16,15);  
       g.drawString("" + rands[2],31,18);  
       g.drawString("" + rands[3],46,16);  
//       g.drawString("" + rands[4],61,14);  
//       g.drawString("" + rands[5],76,19);  

      // //System.out.println(rands);  
    }  

private void drawBackground(Graphics g)  
 
    {  
        //画背景  
       g.setColor(new Color(0xDCDCDC));  
       g.fillRect(0, 0, WIDTH, HEIGHT);  

       //随机产生120个干扰点  
       for(int i=0; i<120; i++)  

       {  
          int x = (int)(Math.random() * WIDTH);  

          int y = (int)(Math.random() * HEIGHT);  

          int red = (int)(Math.random() * 255);  

          int green = (int)(Math.random() * 255);  

          int blue = (int)(Math.random() * 255);  

          g.setColor(new Color(red,green,blue));          

          g.drawOval(x,y,1,0);  

       }  
         
       //加两条干扰线  
       g.drawLine(0, 5, 90, 5);  
       g.drawLine(0, 15, 90, 15);  

    }  

}




jsp代码：


<img width="66" height="20" onclick="changeImg();" style="cursor:hand;" title='看不清楚? align="middle" id='imgsrc' src="ImgValidateServlet" />



附件是一个完整的工程，不过是我个性的设置，大家可以根据这个例子自己改一下！！！

至于字体（附件有 验证码支持的字体）、颜色、几位数、图片大小 等问题 自己修改 servlet内容即可！！！