一 验证码的由来
在web项目开发中，为了防止部分人使用自动工具（如：自动注册机）等进行批量的数据处理，在不同的功能节点部分，添加了验证码进行验证，达到对自动软件的屏蔽效果
最经典的应用如：网站注册图形验证码；接下来，通过java技术，结合servlet实现一个网站注册需要的图形验证码程序，提供大家参考。
二 实现注册页面图形验证码效果
1. 创建web项目：java_servlet_verifyimg
2. 创建自动生成图形验证码的控制器——verifyimgservlet
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package com.phome.util;
import java.awt.color;
import java.awt.font;
import java.awt.graphics2d;
import java.awt.image.bufferedimage;
import java.io.ioexception;
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 com.sun.image.codec.jpeg.jpegcodec;
import com.sun.image.codec.jpeg.jpegimageencoder;
public class verifyimgservlet extends httpservlet {
/**
*
*/
private static final long serialversionuid = 1l;
// 设置随机字符字典。其中不包含0,o,1,i等难以辨认的字符
public static final char[] chars = { '2', '3', '4', '5', '6', '7', '8',
'9', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'j', 'k', 'l', 'm',
'n', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 'a',
'b', 'c', 'd', 'e', 'f', 'g', 'h', 'j', 'k', 'l', 'm', 'n', 'p',
'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z' };
public static random random = new random(); // 随机数对象
public static string getrandomstring() {
stringbuffer buffer = new stringbuffer(); // 字符串缓存
for (int i = 0; i < 6; i++) // 六次循环获取字符
{
buffer.append(chars[random.nextint(chars.length)]); // 每次随机取一个字符
}
return buffer.tostring();
}
public static color getrandomcolor() {
return new color(random.nextint(255), random.nextint(255),
random.nextint(255));
}
public static color getreversecolor(color c) {
return new color(255 - c.getred(), 255 - c.getgreen(),
255 - c.getblue());
}
public void doget(httpservletrequest request, httpservletresponse response)
throws servletexception, ioexception {
response.setcontenttype("image/jpeg"); // 设置输出类型 不可省略
string randomstring = getrandomstring(); // 调用生成随机字符串方法获取并接受随机字符串
request.getsession(true).setattribute("randomstring", randomstring); // 将字符串存储到session中
int width = 100; // 图片宽度
int height = 30; // 图片高度
color color = getrandomcolor(); // 获取随机颜色 用于背景色
color reverse = getreversecolor(color); // 反色 用于前景色
bufferedimage bi = new bufferedimage(width, height,
bufferedimage.type_int_rgb); // 创建一个彩色图片
graphics2d g = bi.creategraphics(); // 获取绘图对象
g.setfont(new font(font.sans_serif, font.bold, 16)); // 设置字体
g.setcolor(color); // 设置颜色
g.fillrect(0, 0, width, height); // 绘制背景
g.setcolor(reverse); // 设置颜色
g.drawstring(randomstring, 18, 20); // 绘制随机字符
for (int i = 0, n = random.nextint(100); i < n; i++) // 画最多一百个噪音点
{
g.drawrect(random.nextint(width), random.nextint(height), 1, 1); // 随机噪音点
}
servletoutputstream out = response.getoutputstream(); // 好像是获取输出流
jpegimageencoder encoder = jpegcodec.createjpegencoder(out); // 编码器
encoder.encode(bi); // 对图片进行编码
out.flush(); // 输出到客户端
}
public void dopost(httpservletrequest request, httpservletresponse response)
throws servletexception, ioexception {
this.doget(request, response);
}
}
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3. 创建注册控制器——registservlet
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package com.phome.servlet;
import java.io.ioexception;
import javax.servlet.servletexception;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import javax.servlet.http.httpsession;
/**
* 注册控制器
* @author zuoyi
*
*/
public class registservlet extends httpservlet{
/**
*
*/
private static final long serialversionuid = 1l;
@override
protected void doget(httpservletrequest req, httpservletresponse resp)
throws servletexception, ioexception {
this.dopost(req, resp);
}
@override
protected void dopost(httpservletrequest req, httpservletresponse resp)
throws servletexception, ioexception {
// 从session中获取注册随机验证码
httpsession session = req.getsession();
string randomstring = (string)session.getattribute("randomstring");
// 获取用户输入验证码
string inputrandomstring = req.getparameter("randomstr");
// 判断验证码通过，模拟进行注册
if (randomstring.equals(inputrandomstring)) {
req.setattribute("resinfo", "恭喜！注册成功！");
} else {
req.setattribute("resinfo", "验证码输入有误，请检查后重新进行注册！");
}
// 注册成功或者失败，都跳转到result.jsp页面，查看注册结果。。。
req.getrequestdispatcher("result.jsp").forward(req, resp);
}
}
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4. 配置servlet
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<?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" 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>simg</display-name>
<!-- 配置用户注册servlet -->
<servlet>
<servlet-name>registservlet</servlet-name>
<servlet-class>com.phome.servlet.registservlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>registservlet</servlet-name>
<url-pattern>/regist.action</url-pattern>
</servlet-mapping>
<!-- 配置图形验证码servlet -->
<servlet>
<servlet-name>verifyimg</servlet-name>
<servlet-class>com.phome.servlet.verifyimgservlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>verifyimg</servlet-name>
<url-pattern>/verifyimg.action</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
</web-app>
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5. 创建注册视图测试页面——regist.jsp
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<%@ page language="java" import="java.util.*" pageencoding="gb18030"%>
<%
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%>" rel="external nofollow" rel="external nofollow" >
<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" rel="external nofollow" rel="external nofollow" >
-->
</head>
<body>
<form action="${pagecontext.request.contextpath}/regist.action" method="post">
用户名：<input type="text" name="username"/>
<br />
密码：<input type="text" name="password"/>
<br />
请输入验证码进行注册：
<img src="${pagecontext.request.contextpath }/verifyimg.action"/>
<input type="text" name="randomstr"/>
<br />
<input type="submit" value="regist"/>
</form>
</body>
</html>
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5.1 创建注册结果页面——result.jsp
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<%@ page language="java" import="java.util.*" pageencoding="gb18030"%>
<%
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%>" rel="external nofollow" rel="external nofollow" >
<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" rel="external nofollow" rel="external nofollow" >
-->
</head>
<body>
${requestscope.resinfo }
</body>
</html>
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6.测试
（1）a.打开浏览器，输入测试地址：http://localhost:8080/java_servlet_verifyimg；出现如下图所示页面
b.输入注册账号、密码和验证码后点击regist提交
c.测试结果，跳转会注册页面，提示注册成功
（2）打开注册页面
输入错误注册码
测试结果页面
over!
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持快网idc。
原文链接：http://blog.csdn.net/muwenbin_flex/article/details/19766865
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