业务背景：一次性批量上传多个文件，只请求一次接口,则手动提交到后台

简单说明一个实现思路:

1. 前端vue统一处理多个文件保存到formData对象中，请求后台接口
2. 后台接口使用HttpServletRequest 进行接收，可转化成MultipartHttpServletRequest对象接收前端formData对象

//前端使用的UI组件是Ant Design of Vue的upload组件
<template>
  <div class="clearfix">
    <a-upload
      :multiple="true"
      :before-upload="beforeUpload"
      :list-type="listType"
      :file-list="fileList"
      @preview="handlePreview"
      @change="handleChange"
      @download="handleDownload"
    >
      <div v-if="isMore">
        <a-icon type="plus" />
        <div class="ant-upload-text">文件上传</div>
      </div>
      <div v-if="!isMore && fileList.length < 1">
        <a-icon type="plus" />
        <div class="ant-upload-text">文件上传</div>
      </div>
    </a-upload>
    <a-modal :visible="previewVisible" :footer="null" @cancel="handleCancel">
      <img alt="example" style="width: 100%" :src="previewImage" />
    </a-modal>
  </div>
</template>

JS的核心代码：
handleUpload() {
      const { fileList } = this
      if (fileList.length > 0) {
        var notUploaded = []
        var uploaded = []
        fileList.forEach((item) => {
          if (item.status && item.status === 'done') {
            uploaded.push(item.url)
          } else {
            notUploaded.push(item)
          }
        })
        let formData = new FormData()
        notUploaded.forEach((file, index) => {
          //所有文件保存在formData中
          formData.append(`file${index}`, file.originFileObj)
        })
        console.log('formData', JSON.stringify(formData))
        //请求批量上传接口
        batchUploadFile(formData, this.targetS).then((res) => {
          if (res.success) {
            console.log('res', JSON.stringify(res))
          } else {
            this.$message.error('图片上传失败，请重新上传')
          }
        })
        // return
        //this.$emit('loadImgUrl', this.loadImgUrl.join(','))
        //this.fileList = []
      } else {
        // 如果没有图片则返回空
        //this.$emit('loadImgUrl', '')
        //this.fileList = []
      }
    },

后台代码：

    @ApiOperation(value = "批量文件上传（最多同时上传5个文件）", notes = "批量文件上传")
    @PostMapping("/batchUploadFile/{filePath}")
    public Result<?> batchUploadFile(@ApiParam(value = "自定义上传文件的路径")
                                     @PathVariable("filePath") String filePath,
                                     HttpServletRequest request) throws Exception {
        MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;
        Map<String, MultipartFile> fileMap = multipartRequest.getFileMap();
        if (fileMap.isEmpty()) {
            return Result.error("上传文件不能为空");
        }
        if (fileMap.size() > 5) {
            return Result.error("批量上传文件数量不能超过5个文件");
        }
        List<Map<String, Object>> mapList = ftpUtils.batchUploadFile(fileMap, filePath);
        return Result.OK(mapList);
    }

注意：以上代码部分功能不完全只能作为参考，重点是实现思路
1.前端是如何组装参数

  let formData = new FormData()
        notUploaded.forEach((file, index) => {
          //所有文件保存在formData中
          formData.append(`file${index}`, file.originFileObj) //核心代码
        })

2.后台使用MultipartHttpServletRequest对象进行接受

  MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;
        Map<String, MultipartFile> fileMap = multipartRequest.getFileMap();

前端参数格式：

请求结果：