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javaWeb验证码

2015-09-21 20:48 519 查看

在web开发中，我们经常会用到，验证码的用法。现在就给大家写一个例子。

注：利用到的技术：主要是HttpServlet

jsp主页面：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head><!-- 该函数无法执行的话，可能是没有通知浏览器不要缓存的原因 -->
<script type="text/javascript">
function toreal(){
document.location.href="index.jsp";
}

</script>

<body>
<form action="" method="post">
<input type="text" name="username"><br/>
<input type="password" name="password"><br/>
<input type="text" name="code">
<img alt="验证码" src="/java_Code/servlet/code">
<a href="javascript:toreal()">看不清</a>
<br/>
<input type="submit" value="登录"><br/><!-- 内部自动发送请求，加载验证码 -->

</form>
</body>
</html>

servlet页面生成验证码的图片代码：

package com.dp.java.code;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
* 输出验证码图片
*
*/
public class code extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//通知浏览器不要缓存
response.setHeader("Expires", "-1");
response.setHeader("Cache-Control", "no-cache");
response.setHeader("Pragma", "-1");

int height=25;
int width=120;
//得到一个内存图像BufferedImage
BufferedImage img=new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
//得到一个画笔
Graphics g=img.getGraphics();
//画边框drawRect绘制指定矩形的边框。
g.drawRect(0, 0, width, height);
//填充颜色
g.setColor(Color.RED);
g.fillRect(1, 1, width-2, height-2);
//画干扰线
g.setColor(Color.BLACK);
Random r=new Random();
for(int i=0;i<20;i++)
g.drawLine(r.nextInt(width), r.nextInt(height), r.nextInt(width), r.nextInt(height));
//生成随机数字
g.setColor(Color.BLUE);
g.setFont(new Font("微软雅黑", Font.BOLD|Font.ITALIC, 20));//BOLD加粗，ITALIC斜体
int d=15;
for(int j=0;j<4;j++){
g.drawString(r.nextInt(10)+"", d, 20);
d+=20;
}

//输出打web页面
ImageIO.write(img, "jpg", response.getOutputStream());
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}

}

最后是xml映射文件：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>java_Code</display-name>
<servlet>
<servlet-name>code</servlet-name>
<servlet-class>com.dp.java.code.code</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>code</servlet-name>
<url-pattern>/servlet/code</url-pattern>
</servlet-mapping>

<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>

结果：

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