[原创]如何实现验证码的刷新

 

这是我写的一段脚本，用来刷新验证码的。

<script type="text/javascript" language="javascript">
//重新获取验证字符
function changeImage()
{
//单击触发图片重载事件，完成图片验证码的更换
document.getElementById("imgRandom").src = document.getElementById("imgRandom").src + '?';
}
</script>

 

另附验证码页面代码

 

<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %><%@ page import="java.io.OutputStream "%> <%!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);}%><%try{//设置页面不缓存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);OutputStream os = response.getOutputStream();// 获取图形上下文Graphics g = image.getGraphics();//生成随机类Random random = new Random();// 设定背景色g.setColor(getRandColor(200,250));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(160,200));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);}// 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SESSIONsession.setAttribute("systemrand",sRand);// 图象生效g.dispose();// 输出图象到页面ImageIO.write(image, "JPEG", os);os.flush();os.close();os = null ;response.flushBuffer();out.clear();out  =  pageContext.pushBody();}catch (IllegalStateException e){ System.out.println(e.getMessage()); e.printStackTrace();}%>