动态生成验证码_JSP教程

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推荐:Jsp验证码(检验码)实例代码
利用Apache的一个 开源项目Image Tag Library(http://jakarta.apache.org/taglibs/sandbox/doc/image-doc/intro.html) 下载必要文件 1)下载Jakarta-Taglibs: http://people.apache.org/builds/jakarta-taglibs-sandbox/nightly/ 解压后取出taglibs-image.jar

下面一个实例讲述如何动态生成验证码及验证码是否匹配。

显示验证码的html页面login.html代码如下:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>login.html</title>

<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="this is my page">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">

<!--<link rel="stylesheet" type="text/css" href="./styles.css">-->

</head>

<body>
<center>
<form action="login" method="post">
验证码:<input type="text" name="random"><img src="imgcode">
<br>
<br>
<input type="submit" value="提交">
</form>
</center>
</body>
</html>

动态生成验证码的servlet类RandomCodeServlet.java代码如下:
package iss;


import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.util.Random;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.imageio.*;

public class RandomCodeServlet extends HttpServlet ...{

/** *//**
* Constructor of the object.
*/
public RandomCodeServlet() ...{
super();
}

//验证码图片的宽度
private int width=60;
//验证码图片的高度
private int height=20;

protected void service(HttpServletRequest request,HttpServletResponse response)
throws ServletException,java.io.IOException...{
BufferedImage buffImg=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
Graphics2D g=buffImg.createGraphics();

//创建一个随机数生成器
Random random=new Random();

g.setColor(Color.WHITE);
g.fillRect(0, 0, width, height);

//创建字体,字体的大小应该根据图片的高度来定
Font font=new Font("Times New Roman",Font.PLAIN,18);
//设置字体
g.setFont(font);

//画边框
g.setColor(Color.BLACK);
g.drawRect(0, 0, width-1, height-1);

//随机产生160条干扰线
g.setColor(Color.GRAY);
for(int i=0;i<160;i++)...{
int x=random.nextInt(width);
int y=random.nextInt(height);
int x1=random.nextInt(12);
int y1=random.nextInt(12);
g.drawLine(x, y, x+x1, y+y1);
}

//randomCode用于保存随机产生的验证码
StringBuffer randomCode=new StringBuffer();
int red=0,green=0,blue=0;

//随机产生4位数字的验证码
for(int i=0;i<4;i++)...{
//得到随机产生的验证码数字
String strRand=String.valueOf(random.nextInt(10));

//产生随机的颜色分量来构造颜色值
red=random.nextInt(110);
green=random.nextInt(50);
blue=random.nextInt(50);

//用随机产生的颜色将验证码绘制到图像中
g.setColor(new Color(red,green,blue));
g.drawString(strRand, 13*i+6, 16);

randomCode.append(strRand);
}

//将四位数字的验证码保存到session中
HttpSession session=request.getSession();
session.setAttribute("randomCode", randomCode.toString());

//禁止图像缓存
response.setHeader("Pragma", "no-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);

response.setContentType("image/jpeg");
//将图像输出到servlet输出流中
ServletOutputStream sos=response.getOutputStream();
ImageIO.write(buffImg, "jpeg", sos);
sos.close();

}

}

判断验证码是否匹配的LoginServlet.java代码如下:
package iss;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class LoginServlet extends HttpServlet ...{

/** *//**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException ...{

HttpSession session=request.getSession();
String randomCode=(String)session.getAttribute("randomCode");
if(null==randomCode)...{
response.sendRedirect("login.html");
return;
}
String reqRandom=request.getParameter("random");
response.setCharacterEncoding("gbk");
response.setContentType("text/html;charset=gb2312");
PrintWriter out = response.getWriter();
if(randomCode.equals(reqRandom))...{
out.println("验证码匹配!");
}else...{
out.println("验证码不匹配!");
}

out.close();
}

}

web.xml如下:
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>RandomCodeServlet</servlet-name>
<servlet-class>iss.RandomCodeServlet</servlet-class>
</servlet>
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>iss.LoginServlet</servlet-class>
</servlet>


<servlet-mapping>
<servlet-name>RandomCodeServlet</servlet-name>
<url-pattern>/imgcode</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/login</url-pattern>
</servlet-mapping>
</web-app>

 

分享:网页无闪自动局部刷新实例
我们在网页制作的过程中经常会遇到及时刷新数据的问题,如果使用 meta http-equiv=refresh content=300 的方法,会造成整个屏幕不断闪烁刷新的效果,这会降低用户的操作满意度。所以我们需要一种可以实现无闪自动刷新数据的方法来解决以上问题。 实例解决

来源:模板无忧//所属分类:JSP教程/更新时间:2010-05-31
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