一、什么是session？

Session由服务器创建，并为每一次会话分配一个Session对象。同一个浏览器发起的多次请求，同属于一次会话（Session）。首次使用到Session时，服务器会自动创建Session，并创建Cookie来存储Session ID发送回客户端。Session ID用于唯一标识一个会话，确保在同一个会话中请求被正确地处理。

一台服务器对应多个客户端，服务器如何知道谁是谁 ---》 通过cookies和session进行匹配的

每个测览器访可同一个站点的不同方法的时候都会携带一个cookie，名字叫JSESSICNID给服务器，服务器将JSESSIONID的值作为sesion的id进行存诸，通过这两个进行匹配，找到对应的客户端

先看实现效果是如何滴？

输入验证码，前端发送请求到后端，后端接收，存入session，并且后端校验验证码是否正确，将结果返回前端，并设置了验证码的有效时间为1min，1分钟过后过期

话不多说，来实现这个功能！

二、代码

前端：cookie，后端：session

思路：

前端页面一加载调用验证码的生成（created），输入验证码，点击登录按钮，发送到后端进行处理和判断【首先从session取出来验证码，然后进行判断，返回前端】

验证码用session存，调用验证码的工具类，生成图片验证码，然后将验证码存入session，在设置有效的时间为60s

前端相关的代码：

<el-button @click="doLogin">登录</el-button>
//验证码，点击验证码可以改变<p style="margin-left: 100px">验证码：<input type="text" v-model="code">< class="changeCodeImg" :src="codeUrl" alt="" @click="changeCode"></p>

 data(){return{code:"",codeUrl:"http://localhost:9091/api/code/createCode",}},created(){this.changeCode()},
methods:{//点击图片改变changeCode(){//看你后端接口的路径哦，如果写完了想看路径对不对，可以通过直接访问路径得到验证码图片this.codeUrl="http://localhost:9091/api/code/createCode},
}

重头戏的是后端的啦，看看后端怎么实现🤔

后端相关代码：

点击登录按钮时判断验证码是否正确，返回结果给前端

//controller
//点击登录按钮判断验证码是否正确
@RequestMapping("/login")public ResponseDto login(@RequestBody LoginVo vo, HttpSession session){System.out.println(session.getAttribute("code"));//先判断验证码是否正确，正确在进行账号密码的判断if (vo.getCode().equals(session.getAttribute("code"))){//登录验证码如果成功要做的事情*****}else if (session.getAttribute("code") == null){//ResponseDto是我写的返回消息的工具类return new ResponseDto(-1,"验证码过期",null);}else {return new ResponseDto(2,"验证码错误",null);}}

import com.cykj.util.ImageCodeUtils;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;@RestController
@RequestMapping("/code")
public class CodeController {@RequestMapping("/createCode")public void createCode(HttpServletResponse response, HttpSession session){//生成验证码图片的工具类ImageCodeUtils imageCodeUtils = new ImageCodeUtils();//将验证码存入session中session.setAttribute("code",imageCodeUtils.getCode());//设置有效时间，单位为秒session.setMaxInactiveInterval(60);try {//写回去imageCodeUtils.write(response.getOutputStream());} catch (IOException e) {throw new RuntimeException(e);}}
}

接下来就是工具类

消息返回工具类 

public class ResponseDto {private int code;private String msg;private Object data;public int getCode() {return this.code;}public void setCode(int code) {this.code = code;}public String getMsg() {return this.msg;}public void setMsg(String msg) {this.msg = msg;}public Object getData() {return this.data;}public void setData(Object data) {this.data = data;}public ResponseDto(int code, String msg, Object data) {this.code = code;this.msg = msg;this.data = data;}public String toString() {return "ResponseDto{code=" + this.code + ", msg='" + this.msg + '\'' + ", data=" + this.data + '}';}}

生成验证码工具类

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;/*** @description TODO* @date 2023/12/21 0:38*/
public class ImageCodeUtils {/*** 图片的宽度*/private int width = 160;/*** 图片的高度*/private int height = 40;/*** 验证码字符个数*/private int codeCount = 4;/*** 验证码干扰线数*/private int lineCount = 20;/*** 验证码*/private String code = null;private BufferedImage buffImg = null;Random random = new Random();public ImageCodeUtils() {createImage();}public ImageCodeUtils(int width, int height) {this.width = width;this.height = height;createImage();}public ImageCodeUtils(int width, int height, int codeCount) {this.width = width;this.height = height;this.codeCount = codeCount;createImage();}public ImageCodeUtils(int width, int height, int codeCount, int lineCount) {this.width = width;this.height = height;this.codeCount = codeCount;this.lineCount = lineCount;createImage();}/*** 生成图片*/private void createImage() {// 字体的宽度int fontWidth = width / codeCount;// 字体的高度int fontHeight = height - 5;int codeY = height - 8;// 图像bufferbuffImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);Graphics g = buffImg.getGraphics();// 设置背景色g.setColor(getRandColor(200, 250));g.fillRect(0, 0, width, height);// 设置字体//Font font1 = getFont(fontHeight);Font font = new Font("Fixedsys", Font.BOLD, fontHeight);g.setFont(font);// 设置干扰线for (int i = 0; i < lineCount; i++) {int xs = random.nextInt(width);int ys = random.nextInt(height);int xe = xs + random.nextInt(width);int ye = ys + random.nextInt(height);g.setColor(getRandColor(1, 255));g.drawLine(xs, ys, xe, ye);}// 添加噪点float yawpRate = 0.01f;int area = (int) (yawpRate * width * height);for (int i = 0; i < area; i++) {int x = random.nextInt(width);int y = random.nextInt(height);buffImg.setRGB(x, y, random.nextInt(255));}// 得到随机字符String str1 = randomStr(codeCount);this.code = str1;for (int i = 0; i < codeCount; i++) {String strRand = str1.substring(i, i + 1);g.setColor(getRandColor(1, 255));// a为要画出来的东西，x和y表示要画的东西最左侧字符的基线位于此图形上下文坐标系的 (x, y) 位置处g.drawString(strRand, i*fontWidth+3, codeY);}}/*** 得到随机字符串* @param n* @return*/private String randomStr(int n) {String str1 = "ABCDEFGHJKMNOPQRSTUVWXYZabcdefghjkmnopqrstuvwxyz1234567890";String str2 = "";int len = str1.length() - 1;double r;for (int i = 0; i < n; i++) {r = (Math.random()) * len;str2 = str2 + str1.charAt((int) r);}return str2;}/*** 得到随机颜色* @param fc* @param bc* @return*/private 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);}/*** 产生随机字体*/private Font getFont(int size) {Random random = new Random();Font[] font = new Font[5];font[0] = new Font("Ravie", Font.PLAIN, size);font[1] = new Font("Antique Olive Compact", Font.PLAIN, size);font[2] = new Font("Fixedsys", Font.PLAIN, size);font[3] = new Font("Wide Latin", Font.PLAIN, size);font[4] = new Font("Gill Sans Ultra Bold", Font.PLAIN, size);return font[random.nextInt(5)];}/*** 扭曲方法* @param g* @param w1* @param h1* @param color*/private void shear(Graphics g, int w1, int h1, Color color) {shearX(g, w1, h1, color);shearY(g, w1, h1, color);}private 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 void shearY(Graphics g, int w1, int h1, Color color) {int period = random.nextInt(40) + 10;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);}}}public void write(OutputStream sos) throws IOException {ImageIO.write(buffImg, "png", sos);sos.close();}public BufferedImage getBuffImg() {return buffImg;}public String getCode() {return code.toLowerCase();}
}