hutool 常用工具类 ---（有空看看-含验证码）前端流文件生成图片展示的方法

https://www.hutool.cn/docs/#/

 <dependency>
                <groupId>cn.hutool</groupId>
                <artifactId>hutool-all</artifactId>
                <version>5.4.1</version>
            </dependency>

验证码

后端代码

    @PostMapping("/no2")
    //获取用户信息的方法 用Authentication类
    public void NO2(HttpServletResponse response) throws IOException {
//        HttpHeaders headers = new HttpHeaders();
////        //生成验证码图片
        LineCaptcha lineCaptcha = CaptchaUtil.createLineCaptcha(200, 100);
        //输出code,这里可以存到redis，前端给个随机码 +这个验证码
        Console.log("输出验证码code: "+lineCaptcha.getCode());
        //指定响应头给浏览器
        response.setContentType("image/png");//告诉浏览器输出内容为图片
        response.setHeader("Pragma", "No-cache");//禁止浏览器缓存
        response.setHeader("Cache-Control", "no-cache");
        //输出流文件给前端
        lineCaptcha.write(response.getOutputStream());
    }

前端代码

<template>
  <div>
    <img :src="src" alt="图像的替代文本">
    <button @click="post">更新验证码</button>
  </div>
</template>
<script>
import {photo} from "../../api/index";
import {photo2} from "../../api/index";
export default {
  data() {
    return {
        type:'1',
        src:'https://emoji.cdn.bcebos.com/yunque/hejirukou.jpg',
  }
},
  methods: {

//下载验证码
   async post(){
       try {
          let { response } = await photo();
          const objectUrl = window.URL.createObjectURL(new Blob([response], {type: "image/png"}));
          this.src = objectUrl;     //到这步已经实现图片展示了 
          const a = document.createElement('a');  //模拟生成一个a标签 点就下载
          a.href = objectUrl;
          a.download = '2023.png';
          a.click();
          a.remove();
        } catch (e) {
          console.log(e);
        }
}

}}
</script>
<style>
</style>

常用api

//把one实体类 复制到 userDTO 实体类 ，相同字段会自动赋值过去
import cn.hutool.core.bean.BeanUtil;
BeanUtil.copyProperties(one, userDTO, true);

//判断变量是否为空
import cn.hutool.core.util.StrUtil;
StrUtil.isBlank(username)

import cn.hutool.core.date.DateUtil;
//当前时间加20秒后的时间
DateUtil.offsetSecond(new Date(), 20)
当前时间加2小时后的时间    
DateUtil.offsetHour(new Date(), 2)
    
//输出结果: 2022-06-14 17:28:26

//格式化
import cn.hutool.core.util.StrUtil;
String template = "{}爱{}，就像老鼠爱大米";
String str = StrUtil.format(template, "我", "你"); //str -> 我爱你，就像老鼠爱大米

//字符转json
import cn.hutool.json.JSONUtil;
String html = "{\"name\":\"Something must have been changed since you leave\"}";
JSONObject jsonObject = JSONUtil.parseObj(html);
jsonObject.getStr("name");
System.out.println(jsonObject);


//List转Json，maps是List类型的参数
String json = JSONUtil.toJsonStr(maps);
System.out.println("这是json字符串: "+json);

//Json转List 
//例子: {
//    "items": [
//        {
//            "id": "62f64658923314000118f4f6",
//           "phoneNumber": "15994727178",
//          "captcha": "247743",
//          "state": "SUCCESS",
//            "sendTime": 1660307032
//        }]
//        }
JSONArray objects =JSONUtil.parseArray(json);
List<Map> maps1 = JSONUtil.toList(objects, Map.class);
System.out.println("这是list集合: "+maps1);



String ss="{'items': [{'id':'62f64658923314000118f4f6'}]}";
JSONObject jsonObject = JSONUtil.parseObj(ss);
System.out.println(jsonObject);  //{"items":[{"id":"62f64658923314000118f4f6"}]}
List<Map> maps1 = JSONUtil.toList(jsonObject.getJSONArray("items"), Map.class);
System.out.println("这是list集合: "+maps1);  //这是list集合: [{id=62f64658923314000118f4f6}]--类型 java.util.ArrayList

json转java对象

场景: 接收前端100多个字段的json，直接映射到实体类里面，然后通过Mongo传实体类分别把字段插入到数据库

AcceptCancelationApplyReq req = JSONUtil.toBean(request, AcceptCancelationApplyReq.class);