登录页面图片验证码的实现

验证码图片的生成用页面

<%@ page contentType="image/jpeg" import="java.awt.*,

java.awt.image.*,java.util.*,javax.imageio.*" pageEncoding="UTF-8"%>

<%!

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);

}

%>

<%

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());

out.clear();

out = pageContext.pushBody();

%>

那么登录界面放验证码的image控件直接连接就可以啦：

<img class="pull-right" name="randImage"  id="randImage" src="<%=basePath%>/jsp/image.jsp" border="1" onclick="loadimage()"/>

单击切换图片用js:

function loadimage(){

          document.getElementById("randImage").src="<%=basePath%>jsp/image.jsp?"+Math.random();

      }