jsp中验证码的实现-蒲公英云

jsp中验证码的实现

<%@ page language=”java” import=”java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*“ pageEncoding=”gbk”%>
<%@ page contentType=”image/jpeg;charset=GBK” %>

<%
String path = request.getContextPath();
String basePath = request.getScheme()+”://“+request.getServerName()+”:”+request.getServerPort()+path+”/“;
%>

<!DOCTYPE HTML PUBLIC “-//W3C//DTD HTML 4.01 Transitional//EN”>

My JSP ‘MyJsp.jsp’ starting page

<%!
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);
}
%>

<%

out.clear(); //加上这句
out = pageContext.pushBody(); //还有这句就OK了
//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);

// 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SESSION session.setAttribute("rand",sRand); // 图象生效 g.dispose(); // 输出图象到页面 //ImageIO.setUseCache(true); ServletOutputStream stream = null ; stream = response.getOutputStream(); ImageIO.write(image, "JPEG",stream); %>