1 前言

图形验证码在用户登录模块常见，下面我们来讲解如何在SpringBoot生成图形验证码。

2 实现

2.1 创建图片生成工具类

直接复制即可，若有需要可自行修改

package com.example.animeApi.utils;

import java.awt.*;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.util.Random;

/**
 * 图形验证码生成
 */
public class CheckCodeUtils {
   // 默认验证码字符集
   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'};
   // 默认字符数量
   private final Integer SIZE;
   // 默认干扰线数量
   private final int LINES;
   // 默认宽度
   private final int WIDTH;
   // 默认高度
   private final int HEIGHT;
   // 默认字体大小
   private final int FONT_SIZE;
   // 默认字体倾斜
   private final boolean TILT;

   private final Color BACKGROUND_COLOR;

   /**
    * 初始化基础参数
    *
    * @param builder
    */
   private CheckCodeUtils(Builder builder) {
      SIZE = builder.size;
      LINES = builder.lines;
      WIDTH = builder.width;
      HEIGHT = builder.height;
      FONT_SIZE = builder.fontSize;
      TILT = builder.tilt;
      BACKGROUND_COLOR = builder.backgroundColor;
   }

   /**
    * 实例化构造器对象
    *
    * @return
    */
   public static Builder newBuilder() {
      return new Builder();
   }

   /**
    * @return 生成随机验证码及图片
    * Object[0]：验证码字符串；
    * Object[1]：验证码图片。
    */
   public Object[] createImage() {
      StringBuffer sb = new StringBuffer();
      // 创建空白图片
      BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
      // 获取图片画笔
      Graphics2D graphic = image.createGraphics();
      // 设置抗锯齿
      graphic.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
      // 设置画笔颜色
      graphic.setColor(BACKGROUND_COLOR);
      // 绘制矩形背景
      graphic.fillRect(0, 0, WIDTH, HEIGHT);
      // 画随机字符
      Random ran = new Random();

      //graphic.setBackground(Color.WHITE);

      // 计算每个字符占的宽度，这里预留一个字符的位置用于左右边距
      int codeWidth = WIDTH / (SIZE + 1);
      // 字符所处的y轴的坐标
      int y = HEIGHT * 3 / 4;

      for (int i = 0; i < SIZE; i++) {
         // 设置随机颜色
         graphic.setColor(getRandomColor());
         // 初始化字体
         Font font = new Font(null, Font.BOLD + Font.ITALIC, FONT_SIZE);

         if (TILT) {
            // 随机一个倾斜的角度 -45到45度之间
            int theta = ran.nextInt(45);
            // 随机一个倾斜方向 左或者右
            theta = (ran.nextBoolean() == true) ? theta : -theta;
            AffineTransform affineTransform = new AffineTransform();
            affineTransform.rotate(Math.toRadians(theta), 0, 0);
            font = font.deriveFont(affineTransform);
         }
         // 设置字体大小
         graphic.setFont(font);

         // 计算当前字符绘制的X轴坐标
         int x = (i * codeWidth) + (codeWidth / 2);

         // 取随机字符索引
         int n = ran.nextInt(chars.length);
         // 得到字符文本
         String code = String.valueOf(chars[n]);
         // 画字符
         graphic.drawString(code, x, y);

         // 记录字符
         sb.append(code);
      }
      // 画干扰线
      for (int i = 0; i < LINES; i++) {
         // 设置随机颜色
         graphic.setColor(getRandomColor());
         // 随机画线
         graphic.drawLine(ran.nextInt(WIDTH), ran.nextInt(HEIGHT), ran.nextInt(WIDTH), ran.nextInt(HEIGHT));
      }
      // 返回验证码和图片
      return new Object[]{sb.toString(), image};
      //return new Object[]{sb.toString(), BufferedImageToBase64(image)};
   }

   /**
    * 随机取色
    */
   private Color getRandomColor() {
      Random ran = new Random();
      Color color = new Color(ran.nextInt(256), ran.nextInt(256), ran.nextInt(256));
      return color;
   }

   /**
    * 构造器对象
    */
   public static class Builder {
      // 默认字符数量
      private int size = 4;
      // 默认干扰线数量
      private int lines = 8;
      // 默认宽度
      private int width = 156;
      // 默认高度
      private int height = 40;
      // 默认字体大小
      private int fontSize = 30;
      // 默认字体倾斜
      private boolean tilt = true;
      //背景颜色
      private Color backgroundColor = Color.LIGHT_GRAY;

      public Builder setSize(int size) {
         this.size = size;
         return this;
      }

      public Builder setLines(int lines) {
         this.lines = lines;
         return this;
      }

      public Builder setWidth(int width) {
         this.width = width;
         return this;
      }

      public Builder setHeight(int height) {
         this.height = height;
         return this;
      }

      public Builder setFontSize(int fontSize) {
         this.fontSize = fontSize;
         return this;
      }

      public Builder setTilt(boolean tilt) {
         this.tilt = tilt;
         return this;
      }

      public Builder setBackgroundColor(Color backgroundColor) {
         this.backgroundColor = backgroundColor;
         return this;
      }

      public CheckCodeUtils build() {
         return new CheckCodeUtils(this);
      }
   }
}

2.2 测试

@GetMapping("/code")
public void code(HttpServletResponse resp) {
   /*
   生成验证码
   objs[0]：验证码字符串
   objs[1]：图片验证码
    */
   Object[] objs = CheckCodeUtils.newBuilder().build().createImage();
   System.out.println(objs[0]);

   try {
      // 将图片输出给浏览器
      BufferedImage image = (BufferedImage) objs[1];
      resp.setContentType("image/png");
      OutputStream os = resp.getOutputStream();
      ImageIO.write(image, "png", os);
   } catch (IOException e) {
      e.printStackTrace();
   }
}

2.3 验证码如下