前端：
：limit用来控制上传文件数量的默认一

<template>
    <div class="app-container">
        <el-form :model="queryParams" ref="queryForm" size="small" :inline="true" v-show="showSearch" label-width="68px">
            <el-form-item label="唯一标识" prop="hwplmid">
                <el-input v-model="queryParams.hwplmid" placeholder="请输入唯一标识" clearable @keyup.enter.native="handleQuery" />
            </el-form-item>
            <el-form-item label="文件名" prop="filename">
                <el-input v-model="queryParams.filename" placeholder="请输入文件名" clearable @keyup.enter.native="handleQuery" />
            </el-form-item>
            <el-form-item>
                <el-button type="primary" icon="el-icon-search" size="mini" @click="handleQuery">搜索</el-button>
                <el-button icon="el-icon-refresh" size="mini" @click="resetQuery">重置</el-button>
            </el-form-item>
        </el-form>

        <el-row :gutter="10" class="mb8">
            <el-col :span="1.5">
                <el-button type="primary" plain icon="el-icon-plus" size="mini" @click="handleAdd"
                    v-hasPermi="['system:homeworkplanm:add']">新增</el-button>
            </el-col>
            <el-col :span="1.5">
                <el-button type="success" plain icon="el-icon-edit" size="mini" :disabled="single" @click="handleUpdate"
                    v-hasPermi="['system:homeworkplanm:edit']">修改</el-button>
            </el-col>
            <el-col :span="1.5">
                <el-button type="danger" plain icon="el-icon-delete" size="mini" :disabled="multiple" @click="handleDelete"
                    v-hasPermi="['system:homeworkplanm:remove']">删除</el-button>
            </el-col>
            <el-col :span="1.5">
                <el-button type="warning" plain icon="el-icon-download" size="mini" @click="handleExport"
                    v-hasPermi="['system:homeworkplanm:export']">导出</el-button>
            </el-col>
            <right-toolbar :showSearch.sync="showSearch" @queryTable="getList"></right-toolbar>
        </el-row>

        <el-table v-loading="loading" :data="homeworkplanmList" @selection-change="handleSelectionChange">
            <el-table-column type="selection" width="55" align="center" />
            <el-table-column label="唯一标识" align="center" prop="hwplmid" />

            <el-table-column label="文件" align="center">
                <template slot-scope="scope">
                    <a class="downa" :href="scope.row.filepath">下载</a>
                </template>
            </el-table-column>

            <el-table-column label="文件名" align="center" prop="filename" />
            <el-table-column align="center" prop="remark">
               
                <template #header>
                    <el-tooltip class="item" effect="dark" content="这里可以自定义内容，内容尽量规范（例如：企业*——*单位*——*用处）" placement="top-start">
                    <span class="custom-label">备注<svg-icon icon-class="helpowen"/></span>
                </el-tooltip>  
                </template>
               
            </el-table-column>
            <el-table-column label="操作" align="center" class-name="small-padding fixed-width">
                <template slot-scope="scope">
                    <el-button size="mini" type="text" icon="el-icon-edit" @click="handleUpdate(scope.row)"
                        v-hasPermi="['system:homeworkplanm:edit']">修改</el-button>
                    <el-button size="mini" type="text" icon="el-icon-delete" @click="handleDelete(scope.row)"
                        v-hasPermi="['system:homeworkplanm:remove']">删除</el-button>
                </template>
            </el-table-column>
        </el-table>

        <pagination v-show="total > 0" :total="total" :page.sync="queryParams.pageNum" :limit.sync="queryParams.pageSize"
            @pagination="getList" />

        <!-- 添加或修改作业方案对话框 -->
        <el-dialog :title="title" :visible.sync="open" width="500px" append-to-body>
            <el-form ref="form" :model="form" :rules="rules" label-width="80px">
                <el-form-item label="备注" prop="remark">
                    <el-input v-model="form.remark" type="textarea" placeholder="请输入内容" />
                </el-form-item>
                <el-form-item label="文件" prop="filepath">
                    <el-upload ref="upload" :limit="1" :action="upload.url" :headers="upload.headers"
                        :file-list="upload.fileList" :on-progress="handleFileUploadProgress" :on-success="handleFileSuccess"
                        :auto-upload="false">
                        <el-button slot="trigger" size="small" type="primary">选取文件</el-button>
                        <el-button style="margin-left: 10px;" size="small" type="success" :loading="upload.isUploading"
                            @click="submitUpload">上传到服务器</el-button>
                        <div slot="tip" class="el-upload__tip">只能上传bmp, gif, jpg, jpeg, png, doc, docx, xls, xlsx, ppt,
                            pptx, html, htm, txt, rar, zip, gz, bz2, mp4, avi, rmvb, pdf文件，且不超过3GB</div>
                    </el-upload>
                </el-form-item>

                <el-form-item label="文件名" prop="filename">
                    <el-input disabled v-model="form.filename" placeholder="请输入文件名" />
                </el-form-item>
            </el-form>
            <div slot="footer" class="dialog-footer">
                <el-button type="primary" @click="submitForm">确 定</el-button>
                <el-button @click="cancel">取 消</el-button>
            </div>
        </el-dialog>
    </div>
</template>
  
<script>
import { listHomeworkplanm, getHomeworkplanm, delHomeworkplanm, addHomeworkplanm, updateHomeworkplanm, byidgetInfo } from "@/api/system/homeworkplanm";
import { getToken } from "@/utils/auth";
export default {
    name: "Homeworkplanm",
    data() {
        return {
            // 遮罩层
            loading: true,
            // 选中数组
            ids: [],
            // 非单个禁用
            single: true,
            // 非多个禁用
            multiple: true,
            // 显示搜索条件
            showSearch: true,
            // 总条数
            total: 0,
            // 作业方案表格数据
            homeworkplanmList: [],
            // 弹出层标题
            title: "",
            // 是否显示弹出层
            open: false,
            // 查询参数
            queryParams: {
                pageNum: 1,
                pageSize: 10,
                filepath: null,
                hwplmid: null,
                filename: null
            },
            // 表单参数
            form: {},
            // 表单校验
            rules: {
                remark: [
                    { required: true, message: "描述不能为空", trigger: "blur" }
                ],
                filepath: [
                    { required: true, message: "请选择文件", trigger: "blur" }
                ],
            },
            // 上传参数
            upload: {
                // 是否禁用上传
                isUploading: false,
                // 设置上传的请求头部
                headers: { Authorization: "Bearer " + getToken() },
                // 上传的地址
                url: process.env.VUE_APP_BASE_API + "/file/upload",
                // 上传的文件列表
                fileList: []
            },
        };
    },
    created() {
        this.getList();
    },
    methods: {
        /** 查询作业方案列表 */
        getList() {
            this.loading = true;
            listHomeworkplanm(this.queryParams).then(response => {
                this.homeworkplanmList = response.rows;
                this.total = response.total;
                this.loading = false;
            });
        },
        // 取消按钮
        cancel() {
            this.open = false;
            this.reset();
        },
        // 表单重置
        reset() {
            this.form = {
                createBy: null,
                createTime: null,
                updateTime: null,
                updateBy: null,
                remark: null,
                filepath: null,
                hwplmid: null,
                filename: null
            };
            this.resetForm("form");
        },
        /** 搜索按钮操作 */
        handleQuery() {
            this.queryParams.pageNum = 1;
            this.getList();
        },
        /** 重置按钮操作 */
        resetQuery() {
            this.resetForm("queryForm");
            this.handleQuery();
        },
        // 多选框选中数据
        handleSelectionChange(selection) {
            this.ids = selection.map(item => item.hwplmid)
            this.single = selection.length !== 1
            this.multiple = !selection.length
        },
        /** 新增按钮操作 */
        handleAdd() {
            this.reset();
            this.open = true;
            this.title = "添加作业方案";
            this.upload.fileList = [];
        },
        /** 修改按钮操作 */
        handleUpdate(row) {
            this.reset();
            const createBy = row.hwplmid || this.ids
            byidgetInfo(createBy).then(response => {
                this.form = response.data;
                this.open = true;
                this.title = "修改作业方案";
            });
            this.upload.fileList = [{ name: this.form.fileName, url: this.form.filePath }];
        },
        /** 提交按钮 */
        submitForm() {
            this.$refs["form"].validate(valid => {
                if (valid) {

                    if (this.form.hwplmid != null) {
                        updateHomeworkplanm(this.form).then(response => {
                            this.$modal.msgSuccess("修改成功");
                            this.open = false;
                            this.getList();
                        });
                    } else {
                        alert(JSON.stringify(this.form))
                        alert(this.form.hwplmid)

                        addHomeworkplanm(this.form).then(response => {
                            this.$modal.msgSuccess("新增成功");
                            this.open = false;
                            this.getList();
                        });
                    }
                }
            });
        },
        /** 删除按钮操作 */
        handleDelete(row) {

            const createBys = row.hwplmid || this.ids;

            this.$modal.confirm('是否确认删除作业方案编号为"' + createBys + '"的数据项？').then(function () {
                return delHomeworkplanm(createBys);
            }).then(() => {
                this.getList();
                this.$modal.msgSuccess("删除成功");
            }).catch(() => { });
        },
        /** 导出按钮操作 */
        handleExport() {
            this.download('system/homeworkplanm/export', {
                ...this.queryParams
            }, `homeworkplanm_${new Date().getTime()}.xlsx`)
        },
        // 文件提交处理
        submitUpload() {
            this.$refs.upload.submit();
        },
        // 文件上传中处理
        handleFileUploadProgress(event, file, fileList) {
            this.upload.isUploading = true;
        },
        // 文件上传成功处理
        handleFileSuccess(response, file, fileList) {
            this.upload.isUploading = false;
            this.form.filepath = response.data.url;
            this.form.filename = response.data.name;
            this.msgSuccess(response.msg);
        }
    }
};
</script>
<style scoped>
.downa:link {
    color: #1890FF;
}

.downa:hover {
    color: red;
}
</style>

后端
若依项目自带的详情自己下载自己去找service层去看吧

 package com.ruoyi.file.controller;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;
import com.ruoyi.common.core.domain.R;
import com.ruoyi.common.core.utils.file.FileUtils;
import com.ruoyi.file.service.ISysFileService;
import com.ruoyi.system.api.domain.SysFile;

/**
 * 文件请求处理
 * 
 * @author ruoyi
 */
@RestController
public class SysFileController
{
    private static final Logger log = LoggerFactory.getLogger(SysFileController.class);

    @Autowired
    private ISysFileService sysFileService;

    /**
     * 文件上传请求
     */
    @PostMapping("upload")
    public R<SysFile> upload(MultipartFile file)
    {
        try
        {
            // 上传并返回访问地址
            String url = sysFileService.uploadFile(file);
            SysFile sysFile = new SysFile();
            sysFile.setName(FileUtils.getName(url));
            sysFile.setUrl(url);
            return R.ok(sysFile);
        }
        catch (Exception e)
        {
            log.error("上传文件失败", e);
            return R.fail(e.getMessage());
        }
    }
}