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, fileList) {
   
   
      const findex = this.fileList.map(f => f.name).indexOf(file.name