servlet验证码

作者: simple乐 | 来源:发表于2018-11-07 17:58 被阅读3次

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package com;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
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.JPEGImageDecoder;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
import com.sun.jndi.url.corbaname.corbanameURLContextFactory;

public class servletFirst extends HttpServlet {

private static final long serialVersionUID = 1L;

public static final char[] CHARS = { '1', '2', '3', '4', '5', '6', '7',
        '8', '9', '0', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
        'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',
        'X', 'Y', 'Z', };
public static Random random = new Random();

public static String getRandomString() {
    StringBuffer buffer = new StringBuffer();
    for (int i = 0; i < 9; i++) {
        buffer.append(CHARS[random.nextInt(CHARS.length)]);
    }
    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");
    String radomString = getRandomString();
    request.getSession(true).setAttribute("radomString", radomString);
    Color color = getRandomColor();
    Color reverse = getReverseColor(color);
    BufferedImage bi = new BufferedImage(100, 30, BufferedImage.TYPE_INT_RGB);
    Graphics2D g = bi.createGraphics();
    g.setFont(new Font(Font.SANS_SERIF,Font.BOLD,16));
    g.setColor(color);
    g.fillRect(0,0,100,30);
    g.setColor(reverse);
    g.drawString(radomString,18,20);
    for (int i = 0,n = random.nextInt(100); i<n; i++) {
        g.drawRect(random.nextInt(100), random.nextInt(30), 1, 1);
    }
    ServletOutputStream out = response.getOutputStream();
    JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
    encoder.encode(bi);
    out.flush();
}

}

<%@ page language="java" contentType="text/html; charset=GBK" pageEncoding="GBK"%>
<%
String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + request.getContextPath() + "/";
%>
<%@ taglib prefix="s" uri="/struts-tags"%>
<html>
<head>
<base href="<%=basePath%>">
<title>实训管理系统</title>
<link rel="stylesheet" type="text/css" href="css/team.css" />
<script type="text/javascript">
function changeValidateCode(obj) {
/***

获取当前的时间作为参数，无具体意义
每次请求需要一个不同的参数，否则可能会返回同样的验证码
这和浏览器的缓存机制有关系，也可以把页面设置为不缓存，这样就不用这个参数了。
*/
var timenow = new Date().getTime();

obj.src="LoginCode.servlet?d="+timenow;
}
</script>
</head>
<body>
<div id="top">
<h1>实训管理系统</h1>
</div>
<div id="content">
<form action="admin/Login" method="post">
<p>用户：<input type="text" name="admin.name">
<p>密码：<input type="password" name="admin.password">
<p>验证码：<input type="text" name="code" size="11"><img src="LoginCode.servlet" onclick="changeValidateCode(this)" title="点击图片刷新验证码"/>
<p><input type="submit" value="登录"><input type="reset" value="重置"/></p>
</form>
</div>
</body>
</html>

public class LoginCodeServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {  
     //设置输出类型和浏览器不保存缓存
     response.setContentType("image/jpeg") ;
     response.setHeader("Cache-Control", "no-cache") ;
     
     //创建图片对象
     int width = 60,height = 20 ;
     BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB) ;
     
     Graphics g = image.getGraphics() ;
     
     //生成随机数
     Random random = new Random() ;
     String s = "" ;
     for(int i=0;i<4;i++){
         s += random.nextInt(10) ;
     }
     
     //把随机数存到Session里面，便于等下比较
     HttpSession session = request.getSession() ;
     session.setAttribute("code",s) ;
     
     //随机生成颜色  Color color =  new Color(255,255,255) ;     random.nextInt(256)的值范围是0~255
     Color color = new Color(random.nextInt(256),random.nextInt(256),random.nextInt(256)) ;
     
     //把随机数写到图片上
     String a = null ;
     Font font = new Font(a,Font.ITALIC,18) ;
     g.setColor(color) ;
     g.setFont(font);
     g.drawString(s,10,height-5) ;
     g.dispose() ;    //关闭画笔
     
     //把图片送到客户端
     ServletOutputStream output = response.getOutputStream() ;
     ImageIO.write(image,"JPEG",output) ;
     output.flush();   //关闭输出流
}

}