JSP登录所需要的验证码，java验证码，JSP内写的验证码

首先我们编写一个登录的JSP

login.jsp

<script language="javascript">
   function loadimage(){
      document.getElementById("randImage").src = "image.jsp?"+Math.random();
   }
</script>

<div><font color="red">${msg }</font></div>
    <form action="login.do" method="post">
    UserName:<input type="text" name="userName"/></br>
    PaddWord:<input type="text" name="pwd"/></br>
    <img alt="code..." name="randImage" id="randImage" src="image.jsp" width="60" height="20" border="1" align="absmiddle">
       <a href="javascript:loadimage();"><font class=pt95>看不清点我</font></a>
   <input type="hidden" value="login" name="method"/></br>
    <input type="submit" value="提交"/><input type="reset" value="重置"/></br>
    </form>

其次我们编写一个image.jsp，这是JSP生成验证码的JSP


<%@ page contentType="image/jpeg" import="java.awt.*,
java.awt.image.*,java.util.*,javax.imageio.*" pageEncoding="gbk"%>
<%!
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);
}
%>
<%
out.clear();//这句针对resin服务器，如果是tomacat可以不要这句
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);

int width=60, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);


Graphics g = image.getGraphics();
Random random = new Random();

g.setColor(getRandColor(200,250));
g.fillRect(0, 0, width, height);

g.setFont(new Font("Times New Roman",Font.PLAIN,18));


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);
}


String sRand="";
for (int i=0;i<4;i++){
String rand=String.valueOf(random.nextInt(10));
sRand+=rand;

g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
g.drawString(rand,13*i+6,16);
}

// 将认证码存入SESSION
session.setAttribute("rand",sRand);

g.dispose();

ImageIO.write(image, "JPEG", response.getOutputStream());
%>