我爱Java系列---【Java生成验证码案例】

需求: 在访问登录页面时，需要生产验证码。从而防止用户使用程序恶意登录。

代码演示：

1.页面代码：

<html>
<head>
    <title>登录页面</title>
    <style type="text/css">
        .biao{
              500px;
            height: 300px;
            border: 2px solid black;
            margin: 100px auto;
            align-items: center;
        }
        .login{
            margin: 0 auto;
        }
    </style>
</head>
<body>
<form action="/web11/userlogin" method="post" class="biao">

    <div class="login" >
   用户名：<input type="text" class="userName" name="userName" value="" placeholder="请输入用户名"></br>
   密　码：<input type="password" name="passWord" value="" placeholder="请输入密码"></br>
   验证码：<input type="text" class="userName" name="userName" value="" placeholder="请输入验证码">
    </div>

    <div class="form-group">
        <div class="col-sm-3">
            <img src="/web11/checkcode" onclick="changeImg(this)"/>
        </div>
    </div>

    <input type="submit" value="登录" >
</form>
</body>

<script type="text/javascript">
    function changeImg(obj) {
        // alert("切换验证码");
        //修改修改src
        obj.src = "/web11/checkcode?time=" + Date.now();
    }
</script>
</html>
2.Servlet代码
@WebServlet(urlPatterns = "/checkcode")

public class CheckServlet extends HttpServlet {

protected void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doGet(request, response);

}

protected void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

String t = request.getParameter("t");

System.out.println("time : " + t);

// 生成随机字符 ,打印到控制台

String code = getCodeString();

System.out.println(code);

// 生成图片

BufferedImage checkImg = ImgUtils.getCheckImg(code);

// 将画布显示在浏览器中

ImageIO.write(checkImg, "jpg", response.getOutputStream());

}

public String getCodeString() {

// 准备数据

String data = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";

// 准备随机对象

Random r = new Random();

// 声明一个变量保存验证码

StringBuilder code = new StringBuilder();

// 书写4个随机字符

for (int i = 0; i < 4; i++) {

// 将新的字符保存到验证码中

code.append(data.charAt(r.nextInt(data.length())));

}

return code.toString();

}

}

3.工具类代码

package util;

import java.awt.*;

import java.awt.image.BufferedImage;

import java.util.Random;

public class ImgUtils {

public static BufferedImage getCheckImg(String code) {

Random r = new Random();

// 创建画布

int width = 120;

int height = 40;

BufferedImage bufferedImage = new BufferedImage(width, height,

BufferedImage.TYPE_INT_RGB);// 获得画笔

Graphics g = bufferedImage.getGraphics();

// 填充背景颜色

g.setColor(Color.orange);

g.fillRect(0, 0, width, height);

// 绘制边框

g.setColor(Color.BLACK);

g.drawRect(0, 0, width - 1, height - 1);

// 设置字体

g.setFont(new Font("宋体", Font.BOLD, 28));

// 绘制干扰线

for (int i = 0; i < 6; i++) {

// 设置随机颜色

g.setColor(new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255)));

g.drawLine(r.nextInt(width), r.nextInt(height), r.nextInt(width),

r.nextInt(height));

}

// 书写4个字符

for (int i = 0; i < 4; i++) {

String ch = code.charAt(i) + "";

// 设置随机颜色

g.setColor(new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255)));

g.drawString(ch, 10 + i * 28, 30);

}

return bufferedImage;

}

}

愿你走出半生，归来仍是少年！