<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" pageEncoding="UTF-8" %>
<%!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)
}%>
<%
//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 = 80, 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.BOLD, 18))
//画边框
g.setColor(new Color(0, 0, 0))
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 = 0i <155i++) {
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 = 0i <4i++) {
String rand = null
//随机生成数字或者字母
if (random.nextInt(10) >5) {
rand = String.valueOf((char)(random
.nextInt(10) + 48))
} else {
rand = String.valueOf((char)(random
.nextInt(26) + 65))
}
sRand += rand
// 将认证码显示到图象中
g.setColor(new Color(random.nextInt(80), random
.nextInt(80), random.nextInt(80)))
//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, 15 * i + 10, 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.write(image, "JPEG", response.getOutputStream())
%>
使用验证码图片的文件a.jsp
<%@ page contentType="text/htmlcharset=gb2312" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>认证码输入页面</title>
<meta http-equiv="Content-Type" content="text/htmlcharset=gb2312">
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<META HTTP-EQUIV="Cache-Control" CONTENT="no-cache">
<META HTTP-EQUIV="Expires" CONTENT="0">
</head>
<body>
<form method=post action="check.jsp">
<table>
<tr>
<td align=left>系统产生的认证码：</td>
<td><img id="code" border=0 src="image.jsp"><a href="#" onClick="javascript:var dt=new Date()document.getElementById('code').src='image.jsp?dt='+dt">看不清验证码请单击这里</a></td>
<!--这里的image.jsp?dt='+dt很重要，如果只是改为image.jsp则不会有图片改变的效果，因为浏览器认为SRC没有改变，所以一定要生成一个随时在改变的dt来实现这一功能-->
</tr>
<tr>
<td align=left>输入上面的认证码：</td>
<td><input type=text name=rand maxlength=4 value=""></td>
</tr>
<tr>
<td colspan=2 align=center><input type=submit value="提交检测"></td>
</tr>
</table>
</form>
</body>
</html>
验证的页面check.jsp
<%@ page contentType="text/htmlcharset=gb2312" language="java" import="java.sql.*" errorPage="" %>
<html>
<head>
<title>认证码验证页面</title>
<meta http-equiv="Content-Type" content="text/htmlcharset=gb2312">
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<META HTTP-EQUIV="Cache-Control" CONTENT="no-cache">
<META HTTP-EQUIV="Expires" CONTENT="0">
</head>
<body>
<%
String rand = (String)session.getAttribute("rand")
String input = request.getParameter("rand")
%>
系统产生的认证码为： <%= rand %><br>
您输入的认证码为： <%= input %><br>
<br>
<%
if (rand.equals(input)) {
%>
<font color=green>输入相同，认证成功！</font>
<%
} else {
%>
<font color=red>输入不同，认证失败！</font>
<%
}
%>
</body>
</html>
这个一定可以的，也符合你的要求
分类: 电脑/网络 >>程序设计 >>其他编程语言问题描述:
写了一个Servlet用来生成图片验证码，在register.jsp中使用，在regdo.jsp页面用rand =(String)application.getAttribute("rand")来接生成的验证码，用num = request.getParameter("num")来接输入的验证码，进行比较，在本地计算机测试没问题，可是放上服务器后偶尔会出现验证码输入错误的问题，过段时间就好了，请问这是为什么？谢谢！
解析:
起servlet服务吧
首页
<img src=RandomCodeCtrl/>
web.xml
<servlet>
<servlet-name>RandomCodeCtrl</servlet-name>
<servlet-class>.chainway.util.RandomCodeCtrl</servlet-class>
<load-on-startup>4</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>RandomCodeCtrl</servlet-name>
<url-pattern>/RandomCodeCtrl</url-pattern>
</servlet-mapping>
RandomCodeCtrl:
package .chainway.util
import java.io.IOException
import javax.servlet.ServletException
import javax.servlet..HttpServlet
import javax.servlet..HttpServletRequest
import javax.servlet..HttpServletResponse
public class RandomCodeCtrl extends HttpServlet {
private static final long serialVersionUID = 1L
protected void doGet(HttpServletRequest req,HttpServletResponse resp) throws ServletException, IOException {
resp.setContentType("image/jpeg")
resp.setHeader("Pragma","No-cache")
resp.setHeader("Cache-Control","no-cache")
resp.setDateHeader("Expires", 0)
RandomCode rc = new RandomCode()
try{
rc.getRandcode(req,resp)
}catch(Exception e){
System.err.println(e)
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response)
}
}
生成类
数字文字图片验证码
package .chainway.util
import java.awt.Color
import java.awt.Font
import java.awt.Graphics
import java.awt.image.BufferedImage
import java.util.Random
import javax.imageio.ImageIO
import javax.servlet..HttpServletRequest
import javax.servlet..HttpServletResponse
import javax.servlet..HttpSession
public class RandomCode {
/**
* 随机取得一个字体
* @param Random random 随机数
* @return Font 返回一个新字体
*/
private synchronized Font getsFont(Random random){
return new Font("Fixedsys",Font.CENTER_BASELINE,18)
}
/**
* 返回一个随机颜色
* @param int fc 随机数
* @param int bc 随机数
* @param Random random 随机数
* @return Color 返回一个新颜色
*/
synchronized Color getRandColor(int fc,int bc,Random random){
if(fc>255) fc=255
if(bc>255) bc=255
int r=fc+random.nextInt(bc-fc-6)
int g=fc+random.nextInt(bc-fc-4)
int b=fc+random.nextInt(bc-fc-8)
return new Color(r,g,b)
}
/**
* 生成随机数图片
*/
public synchronized void getRandcode(HttpServletRequest request,HttpServletResponse response)throws Exception{
System.setProperty("java.awt.headless","true")
HttpSession session = request.getSession()
int width=80, height=26设置图片大小
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB)
Graphics g = image.getGraphics()
Random random = new Random()
g.fillRect(0, 0, width, height)设定边框
g.setFont(new Font("Times New Roman",Font.ROMAN_BASELINE,18))
g.setColor(getRandColor(111,133,random))
产生随机线
for (int i=0i<11i++){
int x = random.nextInt(width)
int y = random.nextInt(height)
int xl = random.nextInt(13)
int yl = random.nextInt(15)
g.drawLine(x,y,x+xl,y+yl)
}
产生随机点
g.setColor(getRandColor(130,150,random))
产生5个随机数
String sRand=""
for (int i=0i<5i++){
g.setFont(getsFont(random))
g.setColor(new Color(random.nextInt(101),random.nextInt(111),random.nextInt(121)))
String rand=String.valueOf(getRandomString(random.nextInt(36)))
String rand=String.valueOf(getRandomString(random.nextInt(10)))
sRand+=rand
g.translate(random.nextInt(3),random.nextInt(3))
g.drawString(rand,13*i,16)
}
session.removeAttribute("Rand")
session.setAttribute("Rand",sRand)
g.dispose()
ImageIO.write(image, "JPEG", response.getOutputStream())
}
public synchronized String getRandomString(int num){
String randstring = "***********"
String randstring = "***********abcdefghijklmnopqrstuvwxyz"
return String.valueOf(randstring.charAt(num))
}
}
登陆判断方法
从session里面取验证码数字进行比较
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