一、实现思路
- 使用BufferedImage用于在内存中存储生成的验证码图片
- 使用Graphics来进行验证码图片的绘制,并将绘制在图片上的验证码存放到session中用于后续验证
- 最后通过ImageIO将生成的图片进行输出
- 通过页面提交的验证码和存放在session中的验证码对比来进行校验
二、生成验证码
页面通过访问servlet来生成验证码,servlet中的代码如下:
package org.test;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.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * @author worm0527 * 2016-03-22 23:15:54 * 生成验证码 */public class ImageServlet extends HttpServlet{ private static final int IMG_HEIGHT = 100; private static final int IMG_WIDTH = 30; private static final int CODE_LEN = 4; @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doPost(req, resp); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { BufferedImage bi = new BufferedImage(IMG_HEIGHT, IMG_WIDTH, BufferedImage.TYPE_INT_RGB); Graphics graphics = bi.getGraphics(); graphics.setColor(new Color(100, 230, 200)); graphics.fillRect(0, 0, 100, 30); char[] codeChar = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456".toCharArray(); String captcha = ""; Random random = new Random(); for(int i = 0; i < CODE_LEN; i++) { int index = random.nextInt(codeChar.length); graphics.setColor(new Color(random.nextInt(150), random.nextInt(200), random.nextInt(255))); graphics.drawString(codeChar[index] + "", (i * 20) + 15, 20); captcha += codeChar[index]; } req.getSession().setAttribute("code", captcha); ImageIO.write(bi, "JPG", resp.getOutputStream()); }}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
三、校验验证码
通过前台提交的验证码与session中数据进行对比来校验验证码,代码如下:
package org.test;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class CheckCodeServlet extends HttpServlet{ @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doPost(req, resp); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String code = (String) req.getSession().getAttribute("code"); String inputCode = req.getParameter("code"); if(code.toLowerCase().equals(inputCode.toLowerCase())) { req.getRequestDispatcher("/success.jsp").forward(req, resp); } else { req.getRequestDispatcher("/fail.jsp").forward(req, resp); } }}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
验证码提交页面html代码:
<form action="<%=request.getContextPath() %>/checkCode" method="post"> 请输入验证码:<input type="text" name="code"> <input type="submit" value="确定"></form><img alt="验证码" id="scode" src="<%=request.getContextPath() %>/getCode" ><a href="#" onclick="javascript:flushCode();">看不清?</a>
当生成的验证码不清楚时需要刷新重新生成验证码,js代码如下:
function flushCode() { var time = new Date(); document.getElementById("scode").src = "<%=request.getContextPath()%>/getCode?time=" + time;}