Spring boot implements verification code function

1. Create a tool class and configure the verification code related parameters

import java.awt.Color;    
import java.awt.Font;    
import java.awt.Graphics;    
import java.awt.image.BufferedImage;    
import java.util.Random;    
 
    
/**  
 * @author ld  
 *@date November 6, 2017  
 * @param   
 * @desc graphic verification code generation  
 *   
 */       
public class VerifyUtil {    
    // verification code character set      
        private static final char[] chars = {       
            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',       
            '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',      
            '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'};      
        // number of characters      
        private static final int SIZE = 4;      
        // number of interference lines      
        private static final int LINES = 5;      
        // width      
        private static final int WIDTH = 80;      
        // high      
        private static final int HEIGHT = 40;      
        // font size      
        private static final int FONT_SIZE = 30;      
    
        /**   
         * Generate random verification codes and pictures   
         * Object[0]: verification code string;   
         * Object[1]: Captcha image.   
         */      
        public static Object[] createImage() {      
            StringBuffer sb = new StringBuffer();      
            // 1. Create a blank image      
            BufferedImage image = new BufferedImage(      
                    WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);      
            // 2. Get the picture brush      
            Graphics graphic = image.getGraphics();      
            // 3. Set the brush color      
            graphic.setColor(Color.LIGHT_GRAY);      
            // 4. Draw a rectangle background      
            graphic.fillRect(0, 0, WIDTH, HEIGHT);      
            // 5. Draw random characters      
            Random ran = new Random();      
            for (int i = 0; i <SIZE; i++) {      
                // get random character index      
                int n = ran.nextInt(chars.length);      
                // set random color      
                graphic.setColor(getRandomColor());      
                // set font size      
                graphic.setFont(new Font(      
                        null, Font.BOLD + Font.ITALIC, FONT_SIZE));      
                // draw characters      
                graphic.drawString(      
                        chars[n] + "", i * WIDTH / SIZE, HEIGHT*2/3);      
                // record characters      
                sb.append(chars[n]);      
            }      
            // 6. Draw the interference line      
            for (int i = 0; i < LINES; i++) {      
                // set random color      
                graphic.setColor(getRandomColor());      
                // draw lines randomly      
                graphic.drawLine(ran.nextInt(WIDTH), ran.nextInt(HEIGHT),      
                        ran.nextInt(WIDTH), ran.nextInt(HEIGHT));      
            }      
            // 7. Return the verification code and picture      
            return new Object[]{sb.toString(), image};      
        }      
    
        /**   
         * Random color selection   
         */      
        public static Color getRandomColor() {      
            Random ran = new Random();      
            Color color = new Color(ran.nextInt(256),       
                    ran.nextInt (256), ran.nextInt (256));      
            return color;      
        }      
    
}

2. Interface

@RequestMapping(value="/createValicode",method=RequestMethod.GET)    
	    public void valicode(HttpServletResponse response,HttpSession session) throws Exception{      
	        //Using the image tool to generate the image      
	        //The first parameter is the generated verification code, and the second parameter is the generated image      
	        Object[] objs = VerifyUtil.createImage();      
	        //Save the verification code to the Session      
	        session.setAttribute("imageCode",objs[0]);     
	            
	        // output the image to the browser      
	        BufferedImage image = (BufferedImage) objs[1];      
	        response.setContentType("image/png");      
	        OutputStream os = response.getOutputStream();      
	        ImageIO.write(image, "png", os);    
	    }   

3. Test page call

<!DOCTYPE html>  
<html>  
<head lang="en">  
    <meta charset="UTF-8" />  
    <title>hello</title>  
</head>  
<body>  
    <h1 th:text="${info}" />  
    <div>  
        <!-- <img alt="This is a picture" src="/img/001.png"/> -->  
        <img alt="验证码" onclick = "this.src='/iot-frame/createValicode?' + Math.floor(Math.random() * 100)" src="/iot-frame/createValicode" />  
    </div>  
    <form action="imgvrifyControllerDefaultKaptcha">  
        <input type="text" name="vrifyCode" />  
        <input type="submit" value="提交"></input>  
    </form>  
</body>  
</html>