【项目背景】

考虑登录时的验证安全，需要添加验证码验证，纯前端实现的验证码其实没有真正意义上做到安全验证的要求，简单一个网页爬虫就能获取到前端生成的验证码，所以应该由后台生成验证码，并由后台完成校验过程。

【实现思路】

登录页面初始化的时候，向后台请求返回base64格式的图片流，渲染到验证码控件上，前端用户输入验证码提交到后台进行对比校验。

【实现过程】

Spring Boot 后端代码

#1#-> 先创建一个验证码图片生成类 VertifyCodeUtils.java

package com.mhwz.utils;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.Random;

public class VertifyCodeUtils {

    //使用到Algerian字体，系统里没有的话需要安装字体，字体只显示大写，去掉了1,0,i,o几个容易混淆的字符
    public static final String VERIFY_CODES = "23456789ABCDEFGHJKLMNPQRSTUVWXYZ";
    private static Random random = new Random();

    /**
     * 使用系统默认字符源生成验证码
     *
     * @param verifySize 验证码长度
     * @return
     */
    public static String generateVerifyCode(int verifySize) {
        return generateVerifyCode(verifySize, VERIFY_CODES);
    }

    /**
     * 使用指定源生成验证码
     *
     * @param verifySize 验证码长度
     * @param sources    验证码字符源
     * @return
     */
    public static String generateVerifyCode(int verifySize, String sources) {
        if (sources == null || sources.length() == 0) {
            sources = VERIFY_CODES;
        }
        int codesLen = sources.length();
        Random rand = new Random(System.currentTimeMillis());
        StringBuilder verifyCode = new StringBuilder(verifySize);
        for (int i = 0; i < verifySize; i++) {
            verifyCode.append(sources.charAt(rand.nextInt(codesLen - 1)));
        }
        return verifyCode.toString();
    }

    /**
     * 生成随机验证码文件,并返回验证码值
     *
     * @param w
     * @param h
     * @param outputFile
     * @param verifySize
     * @return
     * @throws IOException
     */
    public static String outputVerifyImage(int w, int h, File outputFile, int verifySize) throws IOException {
        String verifyCode = generateVerifyCode(verifySize);
        outputImage(w, h, outputFile, verifyCode);
        return verifyCode;
    }

    /**
     * 输出随机验证码图片流,并返回验证码值
     *
     * @param w
     * @param h
     * @param os
     * @param verifySize
     * @return
     * @throws IOException
     */
    public static String outputVerifyImage(int w, int h, OutputStream os, int verifySize) throws IOException {
        String verifyCode = generateVerifyCode(verifySize);
        outputImage(w, h, os, verifyCode);
        return verifyCode;
    }

    /**
     * 生成指定验证码图像文件
     *
     * @param w
     * @param h
     * @param outputFile
     * @param code
     * @throws IOException
     */
    public static void outputImage(int w, int h, File outputFile, String code) throws IOException {
        if (outputFile == null) {
            return;
        }
        File dir = outputFile.getParentFile();
        if (!dir.exists()) {
            dir.mkdirs();
        }
        try {
            outputFile.createNewFile();
            FileOutputStream fos = new FileOutputStream(outputFile);
            outputImage(w, h, fos, code);
            fos.close();
        } catch (IOException e) {
            throw e;
        }
    }

    /**
     * 输出指定验证码图片流
     *
     * @param w
     * @param h
     * @param os
     * @param code
     * @throws IOException
     */
    public static void outputImage(int w, int h, OutputStream os, String code) throws IOException {
        int verifySize = code.length();
        BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
        Random rand = new Random();
        Graphics2D g2 = image.createGraphics();
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        Color[] colors = new Color[5];
        Color[] colorSpaces = new Color[]{Color.WHITE, Color.CYAN,
                Color.GRAY, Color.LIGHT_GRAY, Color.MAGENTA, Color.ORANGE,
                Color.PINK, Color.YELLOW};
        float[] fractions = new float[colors.length];
        for (int i = 0; i < colors.length; i++) {
            colors[i] = colorSpaces[rand.nextInt(colorSpaces.length)];
            fractions[i] = rand.nextFloat();
        }
        Arrays.sort(fractions);

        g2.setColor(Color.GRAY);// 设置边框色
        g2.fillRect(0, 0, w, h);

        Color c = getRandColor(200, 250);
        g2.setColor(c);// 设置背景色
        g2.fillRect(0, 2, w, h - 4);

        //绘制干扰线
        Random random = new Random();
        g2.setColor(getRandColor(160, 200));// 设置线条的颜色
        for (int i = 0; i < 20; i++) {
            int x = random.nextInt(w - 1);
            int y = random.nextInt(h - 1);
            int xl = random.nextInt(6) + 1;
            int yl = random.nextInt(12) + 1;
            g2.drawLine(x, y, x + xl + 40, y + yl + 20);
        }

        // 添加噪点
        float yawpRate = 0.05f;// 噪声率
        int area = (int) (yawpRate * w * h);
        for (int i = 0; i < area; i++) {
            int x = random.nextInt(w);
            int y = random.nextInt(h);
            int rgb = getRandomIntColor();
            image.setRGB(x, y, rgb);
        }

        shear(g2, w, h, c);// 使图片扭曲

        g2.setColor(getRandColor(100, 160));
        int fontSize = h - 4;
        Font font = new Font("Algerian", Font.ITALIC, fontSize);
        g2.setFont(font);
        char[] chars = code.toCharArray();
        for (int i = 0; i < verifySize; i++) {
            AffineTransform affine = new AffineTransform();
            affine.setToRotation(Math.PI / 4 * rand.nextDouble() * (rand.nextBoolean() ? 1 : -1), (w / verifySize) * i + fontSize / 2, h / 2);
            g2.setTransform(affine);
            g2.drawChars(chars, i, 1, ((w - 10) / verifySize) * i + 5, h / 2 + fontSize / 2 - 10);
        }

        g2.dispose();
        ImageIO.write(image, "jpg", os);
    }

    private static Color getRandColor(int fc, int bc) {
        if (fc > 255)
            fc = 255;
        if (bc > 255)
            bc = 255;
        int r = fc + random.nextInt(bc - fc);
        int g = fc + random.nextInt(bc - fc);
        int b = fc + random.nextInt(bc - fc);
        return new Color(r, g, b);
    }

    private static int getRandomIntColor() {
        int[] rgb = getRandomRgb();
        int color = 0;
        for (int c : rgb) {
            color = color << 8;
            color = color | c;
        }
        return color;
    }

    private static int[] getRandomRgb() {
        int[] rgb = new int[3];
        for (int i = 0; i < 3; i++) {
            rgb[i] = random.nextInt(255);
        }
        return rgb;
    }

    private static void shear(Graphics g, int w1, int h1, Color color) {
        shearX(g, w1, h1, color);
        shearY(g, w1, h1, color);
    }

    private static void shearX(Graphics g, int w1, int h1, Color color) {

        int period = random.nextInt(2);

        boolean borderGap = true;
        int frames = 1;
        int phase = random.nextInt(2);

        for (int i = 0; i < h1; i++) {
            double d = (double) (period >> 1)
                    * Math.sin((double) i / (double) period
                    + (6.2831853071795862D * (double) phase)
                    / (double) frames);
            g.copyArea(0, i, w1, 1, (int) d, 0);
            if (borderGap) {
                g.setColor(color);
                g.drawLine((int) d, i, 0, i);
                g.drawLine((int) d + w1, i, w1, i);
            }
        }

    }

    private static void shearY(Graphics g, int w1, int h1, Color color) {

        int period = random.nextInt(40) + 10; // 50;

        boolean borderGap = true;
        int frames = 20;
        int phase = 7;
        for (int i = 0; i < w1; i++) {
            double d = (double) (period >> 1)
                    * Math.sin((double) i / (double) period
                    + (6.2831853071795862D * (double) phase)
                    / (double) frames);
            g.copyArea(i, 0, 1, h1, 0, (int) d);
            if (borderGap) {
                g.setColor(color);
                g.drawLine(i, (int) d, i, 0);
                g.drawLine(i, (int) d + h1, i, h1);
            }

        }

    }
}

#2#->  Controller类 LoginController.java

（1）新增验证码返回接口 /getVertifyCodeImage

// 生成验证码
@GetMapping("/getVertifyCodeImage")
public String getImageCode(HttpServletRequest request) throws IOException{
    // 1. 使用工具类生成验证码
    String code = VertifyCodeUtils.generateVerifyCode(4);
    validate_code = code; // 存放生成的验证码
    // 2. 将验证码放入ServletContext作用域
    request.getServletContext().setAttribute("code", code);
    // 3. 将图片转换成base64格式
    // 字节数组输出流在内存中创建一个字节数组缓冲区，所有发送到输出流的数据保存在该字节数组缓冲区中
    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
    //将得到的验证码，使用工具类生成验证码图片，并放入到字节数组缓存区
    VertifyCodeUtils.outputImage(220,60,byteArrayOutputStream,code);
    //使用spring提供的工具类，将字节缓存数组中的验证码图片流转换成Base64的形式
    //并返回给浏览器
    return "data:image/png;base64," + Base64Utils.encodeToString(byteArrayOutputStream.toByteArray());
}

（2）在原本的登录接口/login中添加验证码校验过程

// 验证成功
if(validate_code_input.equals(validate_code)){
    // 继续验证用户
    return loginService.loginService(user_id,user_pswd);
} else { // 验证失败
    JSONObject obj = new JSONObject();
    obj.put("validate_result", "failed");
    return obj;
}

完整的LoginController.java ​​​​​​

package com.mhwz.controller;

import com.mhwz.service.LoginService;
import com.mhwz.utils.VertifyCodeUtils;
import net.sf.json.JSON;
import net.sf.json.JSONObject;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.util.Base64Utils;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.servlet.http.HttpServletRequest;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Map;

@RestController
public class LoginController {

    private String validate_code = null;

    @Autowired
    LoginService loginService;

    //@GetMapping("hello")
    @RequestMapping("/login")
    public Map<String,Object> loginController(@RequestBody JSONObject data) {

        //System.out.println(data.toString());
        JSONObject jsonObject = new JSONObject();
        jsonObject =  data;

        String user_id = jsonObject.getString("user_id");
        String user_pswd = jsonObject.getString("user_pswd");
        String validate_code_input = jsonObject.getString("vertify_code");

//        System.out.println("validate_code: " + validate_code);
//        System.out.println("validate_code_input: " + validate_code_input);

        // 验证成功
        if(validate_code_input.equals(validate_code)){
            // 继续验证用户
            return loginService.loginService(user_id,user_pswd);
        } else { // 验证失败
            JSONObject obj = new JSONObject();
            obj.put("validate_result", "failed");
            return obj;
        }
    }

    // 生成验证码
    @GetMapping("/getVertifyCodeImage")
    public String getImageCode(HttpServletRequest request) throws IOException{
        // 1. 使用工具类生成验证码
        String code = VertifyCodeUtils.generateVerifyCode(4);
        validate_code = code; // 存放生成的验证码
        // 2. 将验证码放入ServletContext作用域
        request.getServletContext().setAttribute("code", code);
        // 3. 将图片转换成base64格式
        // 字节数组输出流在内存中创建一个字节数组缓冲区，所有发送到输出流的数据保存在该字节数组缓冲区中
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        //将得到的验证码，使用工具类生成验证码图片，并放入到字节数组缓存区
        VertifyCodeUtils.outputImage(220,60,byteArrayOutputStream,code);
        //使用spring提供的工具类，将字节缓存数组中的验证码图片流转换成Base64的形式
        //并返回给浏览器
        return "data:image/png;base64," + Base64Utils.encodeToString(byteArrayOutputStream.toByteArray());
    }
}

 Vue 前端代码

#1#-> 渲染验证码控件

<template>
  <div class="login_container">
    <div class="login_box">
      <!-- 登录表单区域 -->
      <el-form class="login_form" :model="loginForm" :rules="loginFormRules" ref="loginFormRef">
        <!-- 用户名 -->
        <el-form-item prop="user_id">
          <el-input v-model="loginForm.user_id" placeholder="工号" prefix-icon="el-icon-user"></el-input>
        </el-form-item>
        <!-- 密码 -->
        <el-form-item prop="user_pswd">
          <el-input v-model="loginForm.user_pswd" placeholder="密码" prefix-icon="el-icon-lock" show-password></el-input>
        </el-form-item>
        <!-- 验证码 -->
        <el-form-item prop="vertify_code">
          <el-input v-model="loginForm.vertify_code" placeholder="验证码" prefix-icon="el-icon-key">
            <template slot="append">
              <el-image class="login-code" :src="code_url" @click="getVertifyCode" title="看不清？点击切换"></el-image>
            </template>
          </el-input>
        </el-form-item>
        <!--按钮区域-->
        <el-form-item class="btns">
          <el-button class="btn-login" @click="submitLogin('loginFormRef')">登录</el-button>
          <el-button class="btn-reset" @click="resetLoginForm('loginFormRef')">重置</el-button>
        </el-form-item>
      </el-form>
    </div>
  </div>
</template>

#2#-> data里添加对应的code_url字段

<script>
  export default {
    name: 'Login',
    data () {
      return {
        // 验证码图片URL
        code_url: ''
      }
    }
  }
</script>

 #3#-> methods添加获取验证码的请求代码

// 获取验证码
async getVertifyCode () {
    const { data: res } = await this.$http.get('/getVertifyCodeImage/?time=' + Math.random())
    // console.log(res)
    this.code_url = res // 验证码图片渲染
}

#4#-> 初始化加载验证码

created () {
    this.getVertifyCode() // 页面初始化从后端加载验证码
}

【实现效果】

【参考】

SpringBoot+Vue前后端分离Demo（一）：验证码获取及显示 

https://blog.csdn.net/CSRAWD/article/details/113988243

SPRINGBOOT+VUE实现请求后台获取BASE64编码的图片验证码并使用REDIS缓存实现2分钟内有效

https://www.freesion.com/article/20121255549/

前后端分离情况下的图片验证码验证问题

https://blog.csdn.net/jiahao791869610/article/details/79175268

前端+后端：验证码实现

https://www.cnblogs.com/makexu/articles/5314314.html