java登录验证码实现代码

package com.spring.controller;
import java.awt.Color;        
import java.awt.Font;        
import java.awt.Graphics2D;        
import java.awt.image.BufferedImage;        
import java.util.Random;        
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; 
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
@Controller
public class VerifyCodeServlet extends HttpServlet {
  // 验证码图片的宽度。        
    private int width = 60;        
    // 验证码图片的高度。        
    private int height = 20;        
    // 验证码字符个数        
    private int codeCount = 4;        
    private int x = 0;        
    // 字体高度        
    private int fontHeight;        
    private int codeY;        
    char[] codeSequence = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',        
            'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',        
            'X', 'Y', 'Z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };        
    /**      
     * 初始化验证图片属性      
     */       
    public void initxuan() throws ServletException {        
        // 从web.xml中获取初始信息        
        // 宽度        
        String strWidth ="80";        
        // 高度        
        String strHeight ="30";        
        // 字符个数        
        String strCodeCount = "4";        
        // 将配置的信息转换成数值        
        try {        
            if (strWidth != null && strWidth.length() != 0) {        
                width = Integer.parseInt(strWidth);        
            }        
            if (strHeight != null && strHeight.length() != 0) {        
                height = Integer.parseInt(strHeight);        
            }        
            if (strCodeCount != null && strCodeCount.length() != 0) {        
                codeCount = Integer.parseInt(strCodeCount);        
            }        
        } catch (NumberFormatException e) {        
        }        
        x = width / (codeCount + 1);        
        fontHeight = height - 2;        
        codeY = height - 4;        
    }  
    @RequestMapping(value="xuan/verifyCode",method=RequestMethod.GET)
    public void service(HttpServletRequest req, HttpServletResponse resp)        
            throws ServletException, java.io.IOException {
        initxuan();
        // 定义图像buffer        
        BufferedImage buffImg = new BufferedImage(width, height,        
                BufferedImage.TYPE_INT_RGB);        
        Graphics2D g = buffImg.createGraphics();        
        // 创建一个随机数生成器类        
        Random random = new Random();        
        // 将图像填充为白色        
        g.setColor(Color.WHITE);        
        g.fillRect(0, 0, width, height);        
        // 创建字体，字体的大小应该根据图片的高度来定。        
        Font font = new Font("Fixedsys", Font.PLAIN, fontHeight);        
        // 设置字体。        
        g.setFont(font);        
        // 画边框。        
        g.setColor(Color.BLACK);        
        g.drawRect(0, 0, width - 1, height - 1);        
        // 随机产生160条干扰线，使图象中的认证码不易被其它程序探测到。        
        g.setColor(Color.BLACK);        
        for (int i = 0; i < 10; 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);        
        }        
        // randomCode用于保存随机产生的验证码，以便用户登录后进行验证。        
        StringBuffer randomCode = new StringBuffer();        
        int red = 0, green = 0, blue = 0;        
        // 随机产生codeCount数字的验证码。        
        for (int i = 0; i < codeCount; i++) {        
            // 得到随机产生的验证码数字。        
            String strRand = String.valueOf(codeSequence[random.nextInt(36)]);        
            // 产生随机的颜色分量来构造颜色值，这样输出的每位数字的颜色值都将不同。        
            red = random.nextInt(255);        
            green = random.nextInt(255);        
            blue = random.nextInt(255);        
            // 用随机产生的颜色将验证码绘制到图像中。        
            g.setColor(new Color(red, green, blue));        
            g.drawString(strRand, (i + 1) * x, codeY);        
            // 将产生的四个随机数组合在一起。        
            randomCode.append(strRand);        
        }        
        // 将四位数字的验证码保存到Session中。        
        HttpSession session = req.getSession();        
        session.setAttribute("validateCode", randomCode.toString());        
        // 禁止图像缓存。        
        resp.setHeader("Pragma", "no-cache");        
        resp.setHeader("Cache-Control", "no-cache");        
        resp.setDateHeader("Expires", 0);        
        resp.setContentType("image/jpeg");        
        // 将图像输出到Servlet输出流中。        
        ServletOutputStream sos = resp.getOutputStream();        
        ImageIO.write(buffImg, "jpeg", sos);        
        sos.close();        
    }        
}

package com.spring.controller;
import java.io.IOException;        
import java.io.PrintWriter;        
import javax.servlet.ServletException;               
import javax.servlet.http.HttpServletRequest;        
import javax.servlet.http.HttpServletResponse;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
@Controller
public class ResultServlet {
     @RequestMapping(value="resultServlet/validateCode",method=RequestMethod.POST)
     public void doPost(HttpServletRequest request, HttpServletResponse response)        
             throws ServletException, IOException {        
         response.setContentType("text/html;charset=utf-8");        
         String validateC = (String) request.getSession().getAttribute("validateCode");        
         String veryCode = request.getParameter("c");        
         PrintWriter out = response.getWriter();        
         if(veryCode==null||"".equals(veryCode)){        
             out.println("验证码为空");        
         }else{        
             if(validateC.equals(veryCode)){        
                 out.println("验证码正确");        
             }else{        
                 out.println("验证码错误");        
             }        
         }        
         out.flush();        
         out.close();        
     }        
}

<%@ page language="java" contentType="text/html; charset=UTF-8"      
    pageEncoding="UTF-8"%>      
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">      
<html>      
    <head>      
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>test verify code</title> 
    </head> 
    <body>      
        <input id="veryCode" name="veryCode" type="text"/>      
        <img id="imgObj"  alt="" src="xuan/verifyCode"/>      
        <a href="#" onclick="changeImg()">换一张</a>      
        <input type="button" value="验证" onclick="isRightCode()"/>      
        <div id="info"></div>      
    </body>      
</html>
<script type="text/javascript">
 function changeImg(){    
    var imgSrc = $("#imgObj");    
    var src = imgSrc.attr("src");    
    imgSrc.attr("src",chgUrl(src));    
}    
//时间戳    
//为了使每次生成图片不一致，即不让浏览器读缓存，所以需要加上时间戳    
function chgUrl(url){    
    var timestamp = (new Date()).valueOf();    
    urlurl = url.substring(0,17);    
    if((url.indexOf("&")>=0)){    
        urlurl = url + "×tamp=" + timestamp;    
    }else{    
        urlurl = url + "?timestamp=" + timestamp;    
    }    
    return url;    
}    
function isRightCode(){    
    var code = $("#veryCode").attr("value");    
    code = "c=" + code;    
    $.ajax({    
        type:"POST",    
        url:"resultServlet/validateCode",    
        data:code,    
        success:callback    
    });    
}    
function callback(data){    
    $("#info").html(data);    
} 
</script>