CaptcahCode.java

    1. package com.imooc.code;
    3. import javax.imageio.ImageIO;
    4. import javax.servlet.http.HttpServletRequest;
    5. import javax.servlet.http.HttpServletResponse;
    6. import java.awt.*;
    7. import java.awt.font.FontRenderContext;
    8. import java.awt.geom.Rectangle2D;
    9. import java.awt.image.BufferedImage;
    10. import java.io.IOException;
    11. import java.util.Random;
    13. /**
    14.  * 验证码工具类
    15.  */
    16. public class CaptcahCode {
    17.     /**
    18.      * 验证码生成的方法
    19.      * @param response
    20.      * @return
    21.      */
    23.     public static  String drawImage(HttpServletResponse response)  {
    24.         //1、定义以字符串的拼接的StringBuilder
    25.         StringBuilder builder = new StringBuilder();
    26.         //产生4个字符串的随机数
    27.         for (int i = 0; i < 4; i++) {
    28.             builder.append(randomChar());
    29.         }
    30.         String code = builder.toString();
    32.         //2、定义图片的宽度和高度
    33.         int width = 120;
    34.         int height = 25;
    35.         /**
    36.          *建立bufferedImage对象，制定图片的长度和宽度以及色彩,图片的缓冲流
    37.          * 把绘制的每个步骤先写入到缓冲流，然后进行输出，达到高效的目的,TYPE_3BYTE_BGR表示三原色
    38.          */
    39.         BufferedImage bi = new BufferedImage(width,height,BufferedImage.TYPE_3BYTE_BGR);
    41.         //3、获取到Graphic2D 绘制对象，开始绘制验证码
    42.         Graphics2D g = bi.createGraphics();
    44.         //4、设置文字的字体和大小
    45.         Font font = new Font("微软雅黑",Font.PLAIN,20);
    46.         //设置字体的颜色
    47.         Color color = new Color(0,0,0);
    49.         //关联字体属性
    50.         g.setFont(font);
    51.         //关联字体颜色
    52.         g.setColor(color);
    53.         //设置背景
    54.         g.setBackground(new Color(226, 235,240));
    56.         //开始绘制对象
    57.         g.clearRect(0,0,width,height);
    58.         //绘制形状，获取矩形对象
    59.         FontRenderContext context = g.getFontRenderContext();
    60.         Rectangle2D bounds = font.getStringBounds(code,context);
    62.         //计算文字的坐标和间距
    63.         double x = (width - bounds.getWidth())/2;
    64.         double y = (height - bounds.getHeight())/2;
    65.         double ascent = bounds.getY();
    66.         double baseY = y - ascent;
    67.         g.drawString(code,(int)x,(int)baseY);
    69.         //结束绘制
    70.         g.dispose();
    73.         try {
    74.             //这里可能会抛异常，加个try catch,把图片写到response
    75.             ImageIO.write(bi,"jpg",response.getOutputStream());
    76.             //刷新响应流
    77.             response.flushBuffer();
    78.         } catch (IOException e) {
    79.             e.printStackTrace();
    80.         };
    83.         //验证码的对比和存储
    84.         return code;
    85.     }
    87.     /**
    88.      * 此方法用于产生随机字母和数字组合
    89.      * @return
    90.      */
    91.     private static char randomChar(){
    92.         //1、定义验证需要的字母和数字
    93.         String string = "QWERTYUIOPASDFGHJKLZXCVBNM1234567890";
    94.         //2、定义随机对象，随机从字符串长度中选择一个字符
    95.         Random random = new Random();
    96.         return string.charAt(random.nextInt(string.length()));
    97.     }
    100. }

    code.jsp

    1. <%@ page import="com.imooc.code.CaptcahCode" %>
    2. <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    3. <%
    4.     //1、清空浏览器缓存，保证验证码图片来自服务器而不是本地缓存
    5.     response.setHeader("pragma","no-cache");
    6.     response.setHeader("cache-control","no-cache");
    7.     response.setHeader("expires","0");
    9.     //2、调用编写的生成验证码的工具
    10.     String code = CaptcahCode.drawImage(response);
    11.     session.setAttribute("code",code);
    12.     //我这里遇到一个问题，在firefox和ie没问题，用chrome就打不开，而且还报错ERR_INCOMPLETE_CHUNKED_ENCODING,然后执行下面的第三步操作，chrome就可以了...，
    14.     //3、解决getOutputStream异常问题,但是不知道为啥这么些
    15.     out.clear();
    16.     out = pageContext.pushBody();
    18. %>

    index.jsp

    1. <%--
    2.   Created by IntelliJ IDEA.
    3.   User: msi
    4.   Date: 2020/7/4
    5.   Time: 8:47
    6.   To change this template use File | Settings | File Templates.
    7. --%>
    8. <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    9. <html>
    10.   <head>
    11.     <title>验证码</title>
    12.   </head>
    13.   <body>
    14.     <img src="code.jsp" alt="oops" id = "code">
    15.     <a href="javascript:void(0);" onclick="changeCode()">换一张</a>
    16.     <script>
    17.       function changeCode() {
    18.         //这里加?time=是为了避免浏览器缓存而导致加载不出验证码
    19.         document.getElementById("code").src = "code.jsp"+"?time="+new Date().getTime();
    20.       }
    21.     </script>
    22.   </body>
    23. </html>