upload 文件自动上传写法，前后端下载流文件流

<el-upload
          v-model:file-list="fileList"
          :action="app.api+'/student/student/import'"
          :headers="{
       //   'Content-Type': 'multipart/form-data;boundary=----split-boundary', 此处切记不要加，否则会造成后端报错  Required request part 'file' is not present 
          'token':token
          }"
          name="file"//此处默认为file
          class="upload-demo"
          @on-success="handleSuccess"
          :on-error="handleAvatarSuccess"
          :limit="3"
          :on-progress="beforeAvatarUpload"
        >
<!--:auto-upload="false"-->
          <!--          :http-request="replaceRes"-->
          <span v-if="jinDu">
            <el-progress style="width: 245px; height: 19px" :text-inside="true" :stroke-width="20"
                         :percentage="percentage"/>
          </span>
          <span v-if="isUpload" style="color: #59c2c7;cursor:pointer;"
                @click="uploadChangeValue">导入学生学籍信息</span>
          <template #tip>
            <span style="color: #ff8282; margin-left: 20px">{{ importText }}</span>
          </template>
        </el-upload>
<script lang="ts" setup>

//此处后端穿了一个流给前端，所以需要解析一下，然后赋值给一个按钮，在点击时候才下载！！！
const handleSuccess = (response: any) => {
  console.log(response)
  if (Object.values(response.headers)[0] == 'application/vnd.ms-excel;charset=UTF-8') {
    const url = window.URL.createObjectURL(new Blob([response.data]));
    // 创建a标签，并隐藏a标签
    let link = document.createElement('a')
    link.style.display = 'none'
    // a标签的href属性指定下载链接
    link.href = url
    //setAttribute() 方法添加指定的属性，并为其赋指定的值
    // 后缀格式.csv/.xsls要和需要和后端返回格式相同，这里以.csv为例
    link.setAttribute('download', '文件名称.xlsx')
    document.body.appendChild(link)
    link.click()
    document.body.removeChild(link)
  }
};


//此处用于实时监听进度条进度
const beforeAvatarUpload = (event: any) => {
  let loadProgress = Math.floor(event.percent); //这就是当前上传的进度
  //可以进行其他逻辑
  percentage.value = loadProgress;
  importText.value = "学籍信息导入中……";
  if (percentage.value == 100) {
    importText.value = "学籍导入成功！"
  }
};
</script>

    @PostMapping("import")
    @ApiOperation("导入")
    @RequiresPermissions("student:student:import")
    @ApiImplicitParam(name = "file", value = "文件", paramType = "query", dataType = "file")
    public void importExcel(@RequestParam("file") MultipartFile file, HttpServletResponse response) throws Exception {
        UserDetail userDetail = SecurityUser.getUser();
        //保存所有的表单信息、如果表达有错误、将返回给客户端
        if (userWithErrorListInMap == null) {
            userWithErrorListInMap = new HashMap<>();
        }
        //每次都清空数据
        userWithErrorListInMap.put(userDetail.getId(), new ArrayList<>());

        ZsRef<Boolean> hasError = new ZsRef<>();
        new ExcelServiceListener<StudentExcel, StudentEntity>(studentService, file.getInputStream()) {
            private List<RegionEntity> regionList;

            /**
             * 地区编码 去掉末尾的数字0, 用于判断权限
             */
            private String userRegionCodeForPermission;

            private SchoolEntity schoolForPermission;

            @Override
            public void invoke(StudentExcel data, AnalysisContext context) {

                if (regionList == null) {
                    regionList = regionService.selectList(new HashMap<>());
                }
                if (userDetail.getRegionCode() != null) {
                    //去掉地区编码后面的0
                    userRegionCodeForPermission = userDetail.getRegionCode().replaceAll("0+?$", "");
                }

                if (userDetail.getSchoolCode() != null) {
                    schoolForPermission = schoolService.selectByParams("schoolCode", userDetail.getSchoolCode());
                }
                // 校验姓名
                if (data.getName() == null) {
                    hasError.value = true;
                    data.setName(data.getName() + "##名字不能为空, 长度最多四汉字");
                }
                // 校验性别
                if (data.getGender() == 2) {
                    hasError.value = true;
                    data.setGenderStr(data.getGenderStr() + "##性别只能是（男、女）中的一个");
                }

                // 校验身份证号
                if (isEmpty(data.getIdCard()) || data.getIdCard().length() != 18) {
                    hasError.value = true;
                    data.setName(data.getName() + "##身份证长度18位");
                }

                if (isEmpty(data.getNation())) {
                    hasError.value = true;
                    data.setNation(data.getNation() + "##民族不能为空");
                }

                // ************************ 校验地区 *********************************
                // 判断地区表中是否包含含这一项
                RegionEntity region1 = null, region2 = null;
                for (RegionEntity item : regionList) {
                    if (data.getRegion1() != null && data.getRegion1().contains(item.getName())) {
                        region1 = item;
                    }
                    if (data.getRegion2() != null && data.getRegion2().contains(item.getName())) {
                        region2 = item;
                    }
                }
                // RegionEntity region = regionList.stream().filter(r -> r.getName().contains(data.getRegion())).findFirst().orElse(null);
                if (region1 == null) {
                    hasError.value = true;
                    data.setRegion1(data.getRegion1() + "##城市不存在");
                }

                if (region2 == null) {
                    if (data.getRegion1().contains("济源")) {
                        //济源没有区县
                    } else {
                        hasError.value = true;
                        data.setRegion2(data.getRegion2() + "##区县不存在");
                    }
                }

                if (region1 != null && region2 != null) {
                    data.setRegionCode(region2.getCode());
                    //判断地区和学校 是否具备权限
                    if (isNotEmpty(userDetail.getRegionCode())) {
                        if (String.valueOf(data.getRegionCode()).startsWith(userRegionCodeForPermission)) {
                            //具备权限
                        } else {
                            hasError.value = true;
                            data.setRegion2(data.getRegion2() + "##不具备该地区的权限");
                        }
                    }
                }

                //判断是否具备该学校的权限
                if (isNotEmpty(userDetail.getSchoolCode())) {
                    if (isEquals(schoolForPermission.getName(), data.getSchoolName())) {
                        //具备权限
                    } else {
                        hasError.value = true;
                        data.setSchoolName(data.getSchoolName() + "##不具备该学校的权限");
                    }
                } else {
                    //不需要判断学校权限
                }

                if (isEquals(hasError.value, true)) {
                    userWithErrorListInMap.get(userDetail.getId()).add(data);
                } else {
                    //没有错误的才添加
                    super.list.add(data);
                }
            }

            @Override
            public void doAfterAllAnalysed(AnalysisContext context) {
                if (isEquals(hasError.value, true)) {
                    //  有错误, 不入库
                } else {
                    studentService.saveStudentWidthSchoolAndClass(super.list);
                }
            }
        }.start(2);

        if (Objects.equals(hasError.value, true)) {
            String errorFileName = file.getOriginalFilename().replace(".xlsx", "错误提示.xlsx");
            export(response, errorFileName, userWithErrorListInMap.get(userDetail.getId()));
        } else {
            PrintWriter pw = response.getWriter();
            //逻辑删除导入学籍时学籍不存在的学校班级（当前学期）
            schoolService.deleteBySchoolCode();
            gradeClassService.deleteByClassCode();
            //恢复导入学籍时学籍存在但逻辑删除的学校班级（当前学期）
            schoolService.updateBySchoolCode();
            gradeClassService.updateByClassCode();
            pw.write(ZsJson.toJson(new Result<>()));
            pw.close();
        }
        System.out.println("excel解析完成");
    }

下载一个后端返回的流文件

注意跨域问题

后端解决跨域问题

const downLoadExport=()=>{
  axios({
    method: 'post',
    url: baseUrl+"/electric/electricassets/download/assets",
    headers: {
      "Content-Type": "application/json;charset=UTF-8",
      "token":getToken()
    },
    responseType: 'blob'
  }).then(response => {
    if (Object.values(response.headers)[0]=='application/vnd.ms-excel;charset=UTF-8'){
      const url = window.URL.createObjectURL(new Blob([response.data]));
      // 创建a标签，并隐藏a标签
      let link = document.createElement('a')
      link.style.display = 'none'
      // a标签的href属性指定下载链接
      link.href = url
      //setAttribute() 方法添加指定的属性，并为其赋指定的值
      // 后缀格式.csv/.xsls要和需要和后端返回格式相同，这里以.csv为例
      link.setAttribute('download',   '文件名称.xlsx')
      document.body.appendChild(link)
      link.click()
      document.body.removeChild(link)
    }
  })
}