验证码生成步骤：
1、获得随机生成的颜色，画出随机线条生成背景底。
2、String codes = "23456789abcdefghijkmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYXZ";随机选取4个字符构成验证码。随机字符集合中不包括0和o，O，1和l，因为这些不易区分。
3、选取4个字符进行旋转、伸缩后再单个单个绘制；生成4字符验证码。

示例源码：login.jsp---登录表单。

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<html>
<head>
<title>登录页面</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">
 
<script type="text/javascript">
  function myReload() {
    document.getElementById("CreateCheckCode").src = 
        document.getElementById("CreateCheckCode").src+ "?nocache=" + new Date().getTime();
  }
</script>
 
</head>
 
<body>
  <form action="loginServlet" method="get">
      <p class="font tdheight">
        验证码：<input type="text" name="checkCode" style="width:80px;height:35px;"> 
        <img src="pictureCheckCode" id="CreateCheckCode" align="middle" style="margin-top:-10px;"> <br> 
        
        <a href="" onclick="myReload()" style="font-size:12px;color:red;margin-left:156px;">看不清,换一个</a>
      </p>
      <br><input type="submit" value="提交"
            class="font" style="width:240px;height:35px;background:#f19e28">
 
    </form>
</body>
</html>

LoginServlet---处理登录请求。

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
 
/**
 *处理登录请求
 */
@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        request.setCharacterEncoding("UTF-8"); 
        response.setCharacterEncoding("UTF-8");
        
        String code = request.getParameter("checkCode");
        HttpSession session = request.getSession();
        if (!code.equalsIgnoreCase((String) session.getAttribute("randCheckCode"))) {
            request.setAttribute("errormsg", "验证码不正确");
            response.getWriter().println("<script> type='text/javascript'>window.alert('*验证码错误！');window.location.href='login.jsp'</script>");
        }
        response.getWriter().println("<script> type='text/javascript'>window.alert('*用户登录成功！');window.location.href='login.jsp'</script>");
    }
 
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

PictureCheckCode---验证码生成与更新。

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;
import java.awt.geom.Line2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
 
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
 
/**
 *验证码生成与更新
 */
@WebServlet("/pictureCheckCode")
public class PictureCheckCode extends HttpServlet {
 
    private static final long serialVersionUID = 1L;
    
 
    /* 该方法主要作用是获得随机生成的颜色 */
    public Color getRandColor(int s, int e) {
        Random random = new Random();
        if (s > 255)
            s = 255;
        if (e > 255)
            e = 255;
        int r, g, b;
        r = s + random.nextInt(e - s); // 随机生成RGB颜色中的r值
        g = s + random.nextInt(e - s); // 随机生成RGB颜色中的g值
        b = s + random.nextInt(e - s); // 随机生成RGB颜色中的b值
        return new Color(r, g, b);
    }
    
    private Random r = new Random();
    
    // 随机字符集合中不包括0和o，O，1和l，因为这些不易区分 
    private String codes = "23456789abcdefghijkmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYXZ";  
    private char randomChar() {  
        int index = r.nextInt(codes.length());  
        return codes.charAt(index);  
    } 
 
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
 
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 
        request.setCharacterEncoding("UTF-8");
        response.setCharacterEncoding("UTF-8");
        
        // 设置不缓存图片
        response.setHeader("Pragma", "No-cache");
        response.setHeader("Cache-Control", "No-cache");
        response.setDateHeader("Expires", 0);
        
        // 指定生成的响应图片,一定不能缺少这句话,否则错误.
        response.setContentType("image/jpeg");
        int width = 80, height = 35; // 指定生成验证码的宽度和高度
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); // 创建BufferedImage对象,其作用相当于一图片
        Graphics g = image.getGraphics(); // 创建Graphics对象,其作用相当于画笔
        Graphics2D g2d = (Graphics2D) g; // 创建Grapchics2D对象
        
        Random random = new Random();
        Font mfont = new Font("楷体", Font.BOLD, 16); // 定义字体样式
        g.setColor(getRandColor(200, 250));
        g.fillRect(0, 0, width, height); // 绘制背景
        g.setFont(mfont); // 设置字体
        g.setColor(getRandColor(180, 200));
 
        // 绘制100条颜色和位置全部为随机产生的线条,该线条为2f
        for (int i = 0; i < 100; i++) {
            int x = random.nextInt(width - 1);
            int y = random.nextInt(height - 1);
            int x1 = random.nextInt(6) + 1;
            int y1 = random.nextInt(12) + 1;
            BasicStroke bs = new BasicStroke(2f, BasicStroke.CAP_BUTT, BasicStroke.JOIN_BEVEL); // 定制线条样式
            Line2D line = new Line2D.Double(x, y, x + x1, y + y1);
            g2d.setStroke(bs);
            g2d.draw(line); // 绘制直线
        }
        
        
        //用来保存验证码字符串文本内容  
        StringBuilder sb = new StringBuilder();  
        
        for (int i = 0; i < 4; ++i) {// 随机生成4个字符  
            String sTemp = String.valueOf(randomChar());
            sb.append(sTemp);  
            
            Color color = new Color(20 + random.nextInt(110), 20 + random.nextInt(110), random.nextInt(110));
            g.setColor(color);
            // 将生成的随机数进行随机缩放并旋转制定角度 PS.建议不要对文字进行缩放与旋转,因为这样图片可能不正常显示
            
            /* 将文字旋转制定角度 */
            Graphics2D g2d_word = (Graphics2D) g;
            AffineTransform trans = new AffineTransform();
            trans.rotate((45) * 3.14 / 180, 15 * i + 8, 7);
            
            /* 缩放文字 */
            float scaleSize = random.nextFloat() + 0.8f;
            if (scaleSize > 1f)
                scaleSize = 1f;
            trans.scale(scaleSize, scaleSize);
            g2d_word.setTransform(trans);
            g.drawString(sTemp, 15 * i + 18, 14);
        }
        
        HttpSession session = request.getSession(true);
        session.setAttribute("randCheckCode", sb.toString());
        System.out.println("sRand="+sb.toString());
        g.dispose(); // 释放g所占用的系统资源
        ImageIO.write(image, "JPEG", response.getOutputStream()); // 输出图片
    }
 
}

测试：

原文：https://blog.csdn.net/ljheee/article/details/72799746

posted on 2018-08-19 14:23 漂流的老妖怪阅读(601) 评论(0) 编辑收藏举报

刷新页面返回顶部

导航