闲来无事,探究一番若依框架文件上传下载实现原理

前端部分

若依已经封装好了图片和文件上传组件,参照官方文档使用就行

1. 图片上传

<template>
  <div class="component-upload-image">
    <el-upload
      multiple
      :action="uploadImgUrl"
      list-type="picture-card"
      :on-success="handleUploadSuccess"
      :before-upload="handleBeforeUpload"
      :limit="limit"
      :on-error="handleUploadError"
      :on-exceed="handleExceed"
      name="file"
      :on-remove="handleRemove"
      :show-file-list="true"
      :headers="headers"
      :file-list="fileList"
      :on-preview="handlePictureCardPreview"
      :class="{hide: this.fileList.length >= this.limit}"
    >
      <i class="el-icon-plus"></i>
    </el-upload>
    
    <!-- 上传提示 -->
    <div class="el-upload__tip" slot="tip" v-if="showTip">
      请上传
      <template v-if="fileSize"> 大小不超过 <b style="color: #f56c6c">{{ fileSize }}MB</b> </template>
      <template v-if="fileType"> 格式为 <b style="color: #f56c6c">{{ fileType.join("/") }}</b> </template>
      的文件
    </div>

    <el-dialog
      :visible.sync="dialogVisible"
      title="预览"
      width="800"
      append-to-body
    >
      <img
        :src="dialogImageUrl"
        style="display: block; max-width: 100%; margin: 0 auto"
      />
    </el-dialog>
  </div>
</template>

<script>
import { getToken } from "@/utils/auth";

export default {
  props: {
    value: [String, Object, Array],
    // 图片数量限制
    limit: {
      type: Number,
      default: 5,
    },
    // 大小限制(MB)
    fileSize: {
       type: Number,
      default: 5,
    },
    // 文件类型, 例如['png', 'jpg', 'jpeg']
    fileType: {
      type: Array,
      default: () => ["png", "jpg", "jpeg"],
    },
    // 是否显示提示
    isShowTip: {
      type: Boolean,
      default: true
    }
  },
  data() {
    return {
      number: 0,
      uploadList: [],
      dialogImageUrl: "",
      dialogVisible: false,
      hideUpload: false,
      baseUrl: process.env.VUE_APP_BASE_API,
      uploadImgUrl: process.env.VUE_APP_BASE_API + "/common/upload", // 上传的图片服务器地址
      headers: {
        Authorization: "Bearer " + getToken(),
      },
      fileList: []
    };
  },
  watch: {
    value: {
      handler(val) {
        if (val) {
          // 首先将值转为数组
          const list = Array.isArray(val) ? val : this.value.split(',');
          // 然后将数组转为对象数组
          this.fileList = list.map(item => {
            if (typeof item === "string") {
              if (item.indexOf(this.baseUrl) === -1) {
                  item = { name: this.baseUrl + item, url: this.baseUrl + item };
              } else {
                  item = { name: item, url: item };
              }
            }
            return item;
          });
        } else {
          this.fileList = [];
          return [];
        }
      },
      deep: true,
      immediate: true
    }
  },
  computed: {
    // 是否显示提示
    showTip() {
      return this.isShowTip && (this.fileType || this.fileSize);
    },
  },
  methods: {
    // 删除图片
    handleRemove(file,) {
      const findex = this.fileList.map(f => f.name).indexOf(file.name);
      if(findex > -1) {
        this.fileList.splice(findex, 1);
        this.$emit("input", this.listToString(this.fileList));
      }
    },
    // 上传成功回调
    handleUploadSuccess(res) {
      this.uploadList.push({ name: res.fileName, url: res.fileName });
      if (this.uploadList.length === this.number) {
        this.fileList = this.fileList.concat(this.uploadList);
        this.uploadList = [];
        this.number = 0;
        this.$emit("input", this.listToString(this.fileList));
        this.$modal.closeLoading();
      }
    },
    // 上传前loading加载
    handleBeforeUpload(file) {
      let isImg = false;
      if (this.fileType.length) {
        let fileExtension = "";
        if (file.name.lastIndexOf(".") > -1) {
          fileExtension = file.name.slice(file.name.lastIndexOf(".") + 1);
        }
        isImg = this.fileType.some(type => {
          if (file.type.indexOf(type) > -1) return true;
          if (fileExtension && fileExtension.indexOf(type) > -1) return true;
          return false;
        });
      } else {
        isImg = file.type.indexOf("image") > -1;
      }

      if (!isImg) {
        this.$modal.msgError(`文件格式不正确, 请上传${this.fileType.join("/")}图片格式文件!`);
        return false;
      }
      if (this.fileSize) {
        const isLt = file.size / 1024 / 1024 < this.fileSize;
        if (!isLt) {
          this.$modal.msgError(`上传头像图片大小不能超过 ${this.fileSize} MB!`);
          return false;
        }
      }
      this.$modal.loading("正在上传图片，请稍候...");
      this.number++;
    },
    // 文件个数超出
    handleExceed() {
      this.$modal.msgError(`上传文件数量不能超过 ${this.limit} 个!`);
    },
    // 上传失败
    handleUploadError() {
      this.$modal.msgError("上传图片失败，请重试");
      this.$modal.closeLoading();
    },
    // 预览
    handlePictureCardPreview(file) {
      this.dialogImageUrl = file.url;
      this.dialogVisible = true;
    },
    // 对象转成指定字符串分隔
    listToString(list,) {
      let strs = "";
      separator = separator || ",";
      for (let i in list) {
        strs += list[i].url.replace(this.baseUrl, "") + separator;
      }
      return strs != '' ? strs.substr(0, strs.length - 1) : '';
    }
  }
};
</script>
<style scoped lang="scss">
// .el-upload--picture-card 控制加号部分
::v-deep.hide .el-upload--picture-card {
    display: none;
}
// 去掉动画效果
::v-deep .el-list-enter-active,
::v-deep .el-list-leave-active {
    transition: all 0s;
}

::v-deep .el-list-enter, .el-list-leave-active {
    opacity: 0;
    transform: translateY(0);
}
</style>

2.文件上传

<template>
  <div class="upload-file">
    <el-upload
      multiple
      :action="uploadFileUrl"
      :before-upload="handleBeforeUpload"
      :file-list="fileList"
      :limit="limit"
      :on-error="handleUploadError"
      :on-exceed="handleExceed"
      :on-success="handleUploadSuccess"
      :show-file-list="false"
      :headers="headers"
      class="upload-file-uploader"
      ref="upload"
    >
      <!-- 上传按钮 -->
      <el-button size="mini" type="primary">选取文件</el-button>
      <!-- 上传提示 -->
      <div class="el-upload__tip" slot="tip" v-if="showTip">
        请上传
        <template v-if="fileSize"> 大小不超过 <b style="color: #f56c6c">{{ fileSize }}MB</b> </template>
        <template v-if="fileType"> 格式为 <b style="color: #f56c6c">{{ fileType.join("/") }}</b> </template>
        的文件
      </div>
    </el-upload>

    <!-- 文件列表 -->
    <transition-group class="upload-file-list el-upload-list el-upload-list--text" name="el-fade-in-linear" tag="ul">
      <li :key="file.url" class="el-upload-list__item ele-upload-list__item-content" v-for="(file, index) in fileList">
        <el-link :href="`${baseUrl}${file.url}`" :underline="false" target="_blank">
          <span class="el-icon-document"> {{ getFileName(file.name) }} </span>
        </el-link>
        <div class="ele-upload-list__item-content-action">
          <el-link :underline="false" @click="handleDelete(index)" type="danger">删除</el-link>
        </div>
      </li>
    </transition-group>
  </div>
</template>

<script>
import { getToken } from "@/utils/auth";

export default {
  name: "FileUpload",
  props: {
    // 值
    value: [String, Object, Array],
    // 数量限制
    limit: {
      type: Number,
      default: 5,
    },
    // 大小限制(MB)
    fileSize: {
      type: Number,
      default: 5,
    },
    // 文件类型, 例如['png', 'jpg', 'jpeg']
    fileType: {
      type: Array,
      default: () => ["doc", "xls", "ppt", "txt", "pdf"],
    },
    // 是否显示提示
    isShowTip: {
      type: Boolean,
      default: true
    }
  },
  data() {
    return {
      number: 0,
      uploadList: [],
      baseUrl: process.env.VUE_APP_BASE_API,
      uploadFileUrl: process.env.VUE_APP_BASE_API + "/common/upload", // 上传的图片服务器地址
      headers: {
        Authorization: "Bearer " + getToken(),
      },
      fileList: [],
    };
  },
  watch: {
    value: {
      handler(val) {
        if (val) {
          let temp = 1;
          // 首先将值转为数组
          const list = Array.isArray(val) ? val : this.value.split(',');
          // 然后将数组转为对象数组
          this.fileList = list.map(item => {
            if (typeof item === "string") {
              item = { name: item, url: item };
            }
            item.uid = item.uid || new Date().getTime() + temp++;
            return item;
          });
        } else {
          this.fileList = [];
          return [];
        }
      },
      deep: true,
      immediate: true
    }
  },
  computed: {
    // 是否显示提示
    showTip() {
      return this.isShowTip && (this.fileType || this.fileSize);
    },
  },
  methods: {
    // 上传前校检格式和大小
    handleBeforeUpload(file) {
      // 校检文件类型
      if (this.fileType) {
        let fileExtension = "";
        if (file.name.lastIndexOf(".") > -1) {
          fileExtension = file.name.slice(file.name.lastIndexOf(".") + 1);
        }
        const isTypeOk = this.fileType.some((type) => {
          if (file.type.indexOf(type) > -1) return true;
          if (fileExtension && fileExtension.indexOf(type) > -1) return true;
          return false;
        });
        if (!isTypeOk) {
          this.$modal.msgError(`文件格式不正确, 请上传${this.fileType.join("/")}格式文件!`);
          return false;
        }
      }
      // 校检文件大小
      if (this.fileSize) {
        const isLt = file.size / 1024 / 1024 < this.fileSize;
        if (!isLt) {
          this.$modal.msgError(`上传文件大小不能超过 ${this.fileSize} MB!`);
          return false;
        }
      }
      this.$modal.loading("正在上传文件，请稍候...");
      this.number++;
      return true;
    },
    // 文件个数超出
    handleExceed() {
      this.$modal.msgError(`上传文件数量不能超过 ${this.limit} 个!`);
    },
    // 上传失败
    handleUploadError(err) {
      this.$modal.msgError("上传图片失败，请重试");
      this.$modal.closeLoading()
    },
    // 上传成功回调
    handleUploadSuccess(res) {
      this.uploadList.push({ name: res.fileName, url: res.fileName });
      if (this.uploadList.length === this.number) {
        this.fileList = this.fileList.concat(this.uploadList);
        this.uploadList = [];
        this.number = 0;
        this.$emit("input", this.listToString(this.fileList));
        this.$modal.closeLoading();
      }
    },
    // 删除文件
    handleDelete(index) {
      this.fileList.splice(index, 1);
      this.$emit("input", this.listToString(this.fileList));
    },
    // 获取文件名称
    getFileName(name) {
      if (name.lastIndexOf("/") > -1) {
        return name.slice(name.lastIndexOf("/") + 1);
      } else {
        return "";
      }
    },
    // 对象转成指定字符串分隔
    listToString(list,) {
      let strs = "";
      separator = separator || ",";
      for (let i in list) {
        strs += list[i].url + separator;
      }
      return strs != '' ? strs.substr(0, strs.length - 1) : '';
    }
  }
};
</script>

<style scoped lang="scss">
.upload-file-uploader {
  margin-bottom: 5px;
}
.upload-file-list .el-upload-list__item {
  border: 1px solid #e4e7ed;
  line-height: 2;
  margin-bottom: 10px;
  position: relative;
}
.upload-file-list .ele-upload-list__item-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  color: inherit;
}
.ele-upload-list__item-content-action .el-link {
  margin-right: 10px;
}
</style>

process.env.VUE_APP_BASE_API 来自.env.development文件,用于区分多环境

后端部分

其中涉及的工具类大家可以下载若依开源项目获取,这里只梳理思路

1.文件上传

需要将附件信息返回到前端,随前端表单一起提交,提交过程中先保存表单信息,获取到相关记录主键id,然后将附件信息和主键id一起存到附件表

/**
     *  上传附件
     * @author Milo Lee
     * @date 2022/5/31 17:44
     * @param file 文件
     * @param cuDir 目录
     * @return com.sjft.common.model.ResultBody<com.sjft.file.client.model.entity.FileUploadRecord>
     */
    @PostMapping(value = "/common/upload")
    public ResultBody<FileUploadRecord> upload(MultipartFile file, @RequestParam("curDir")String cuDir) {
        //改变文件名称,如果容器选用undertow,需要此操作
        MultipartFile file1 = FileUtils.changeFileName(file, "fileName");
        String name = null;
        try {
            name = FileUploadUtils.upload(pathUpload + cuDir, file1);
        } catch (IOException e) {
            e.printStackTrace();
        }
        //组装返回信息
        String url = domain + filePrefix   + name;
        FileUploadRecord fileAttachment = new FileUploadRecord();
        //上传时间
        fileAttachment.setCreateTime(DateUtil.date());
        //访问url[通过nginx代理,实现访问]
        fileAttachment.setUrl(url);
        //文件保存名[用于下载]
        fileAttachment.setSaveName(name);
        return ResultBody.ok().data(fileAttachment);
    }

2.通用下载

一般在涉及到模块下载这类功能,直接使用通用下载,在存储路径下面新建download文件夹,下载路径=磁盘基础路径+文件名,直接可以定位文件,进行下载

/**
     * 通用下载请求
     * @param fileName 文件名称
     * @param delete 是否删除
     */
    @GetMapping("common/download")
    public void fileDownload(String fileName, Boolean delete, HttpServletResponse response, HttpServletRequest request) {
        try {
            if (!FileUtils.isValidFilename(fileName)) {
                throw new Exception("文件名称非法，不允许下载。"+fileName);
            }
            String realFileName = fileName.substring(fileName.indexOf("_") + 1);
            //这一步,pathDownLoad就是磁盘存储路径前缀,fileName就是文件名称
            String filePath = pathDownLoad + fileName;

            response.setCharacterEncoding("utf-8");
            response.setContentType("multipart/form-data");
            response.setHeader("Content-Disposition",
                    "attachment;fileName=" + FileUtils.setFileDownloadHeader(request, realFileName));
            FileUtils.writeBytes(filePath, response.getOutputStream());
            if (delete) {
                FileUtils.deleteFile(filePath);
            }
        } catch (Exception e) {
            log.error("下载文件失败", e);
        }
    }

3. 普通下载

/**
     * 文件下载请求
     * @author Milo Lee
     * @date 2022/5/28 10:41
     */
    @GetMapping("/common/download/resource")
    public  void resourceDownload(String url, HttpServletRequest request, HttpServletResponse response) throws Exception
    {
        // 文件上传base路径
        String localPath = pathUpload;
        // 下面两步就是将访问url转换为文件在磁盘的存储路径
        String downloadPath = localPath + substringAfter(url, "profile");
        // 下载名称
        String downloadName = substringAfterLast(downloadPath, "/");
        response.setCharacterEncoding("utf-8");
        response.setContentType("multipart/form-data");
        response.setHeader("Content-Disposition",
                "attachment;fileName=" + FileUtils.setFileDownloadHeader(request, downloadName));
        FileUtils.writeBytes(downloadPath, response.getOutputStream());
    }

    public   String substringAfter(String str, String separator) {
        if (StrUtil.isEmpty(str)) {
            return str;
        } else if (separator == null) {
            return "";
        } else {
            int pos = str.indexOf(separator);
            return pos == -1 ? "" : str.substring(pos + separator.length());
        }
    }
    public  String substringAfterLast(String str, String separator) {
        if (StrUtil.isEmpty(str)) {
            return str;
        } else if (StrUtil.isEmpty(separator)) {
            return "";
        } else {
            int pos = str.lastIndexOf(separator);
            return pos != -1 && pos != str.length() - separator.length() ? str.substring(pos + separator.length()) : "";
        }
    }