日常生活中,如网站用户注册、登录、论坛、贴吧发表意见等都需要用到验证码,以下为在eclipse中使用servlet实现简单的数字、字母组合验证码验证:
验证码定义:
验证码: 是一种区分用户是计算机还是人的公共全自动程序。
作用: 可以防止恶意破解密码、刷票、论坛灌水,有效防止某个黑客对某一个特定注册用户用特定程序暴力破解方式进行不断的尝试。
代码实现:
创建以下web工程:
详细代码见下:
文件名: index.jsp:
注:jsp表达式中路径需要使用 request.getContextPath() 来获得绝对路径,意思为范围web项目的根目录,即WebContent,此路径不写程序照样可以正常运行
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
<script type="text/javascript">
function reloadCode(){
var time = new Date().getTime();
document.getElementById("imagecode").src="<%=request.getContextPath()%>/servlet/ImageServlet?d="+time;
}
</script>
</head>
<body>
<form action="<%=request.getContextPath()%>/servlet/LoginServlet" method="get">
验证码:<input type="text" name="checkcode"/>
<img alt="验证码" id="imagecode" src="<%=request.getContextPath()%>/servlet/ImageServlet"/>
<a href="javascript:reloadCode();">看不清楚</a><br>
<input type="submit" value="提交">
</form>
</body>
</html>
类: ImageServlet.java:
package com.mayo;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.jws.WebService;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ImageServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
// 创建图片缓存区
BufferedImage bi = new BufferedImage(68, 22, BufferedImage.TYPE_INT_RGB);
// 创建绘制环境,相当于拿起画笔
Graphics g = bi.getGraphics();
// 设置画笔
Color c = new Color(200, 150, 225);
g.setColor(c);
// 画背景
g.fillRect(0, 0, 68, 22);
// 画内容
// 设置文本
char[] ch = "QWERTYUIOPASDFGHJKLZXCVBNM1234567890".toCharArray();
// 生成随机数
Random r = new Random();
StringBuffer sb = new StringBuffer();
int len = ch.length, index;
for (int i = 0; i < 4; i++) {
index = r.nextInt(len);
g.setColor(new Color(r.nextInt(88), r.nextInt(188), r.nextInt(255)));
// 画字符
g.drawString(ch[index] + "", (i * 15) + 3, 18);
sb.append(ch[index]);
}
request.getSession().setAttribute("piccode", sb.toString());
// 输出图片
ImageIO.write(bi, "JPG", response.getOutputStream());
}
}
类:LoginServlet.java:
package com.mayo;
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;
public class LoginServlet extends HttpServlet{
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获得原验证码信息
String piccode = (String) request.getSession().getAttribute("piccode");
//获得用户输入的信息
String checkcode = request.getParameter("checkcode");
checkcode = checkcode.toUpperCase();
response.setContentType("text/html;charset=utf-8");
//判断
PrintWriter out = response.getWriter();
if(checkcode.equals(piccode)){
out.println("验证码输入正确!!");
}else{
out.print("验证码输入错误!!");
}
out.flush();
out.close();
}
}
配置文件:web.xml:
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
<display-name>check</display-name>
<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>
<servlet>
<servlet-name>ImageServlet</servlet-name>
<servlet-class>com.mayo.ImageServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ImageServlet</servlet-name>
<url-pattern>/servlet/ImageServlet</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>com.mayo.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/servlet/LoginServlet</url-pattern>
</servlet-mapping>
</web-app>