<el-upload
       class="upload-demo"
       action=""
       :before-upload="beforeUpload" //上傳前操作
       :before-remove="beforeRemove" //移除錢操作
       :multiple="false"  //禁止多選
       :http-request="myUpload" //文件上傳,重寫文件上傳方法,action的路徑不會起作用
       accept=".jar"  //限制文件選擇類型
       :drag="false"
       :data="param" //參數(shù)
       :file-list="fileList">//文件顯示列表
       <el-button size="small" type="primary">點擊上傳</el-button>
       <div slot="tip" class="el-upload__tip">只能上傳jar文件，且不超過500kb</div><!-- :headers="head"-->
      </el-upload><!--:on-preview="handlePreview"-->

   /*文件上傳前,判斷文件名是否存在,等其他處理*/
   beforeUpload(file){
    console.log("文件名",file.name,this.fileList)
    for (let i = 0; i <this.fileList.length ; i++) {
     if (this.fileList[i].name==file.name) {
      this.$message.info("文件已存在");
      return false;
     }
    }
    this.file=file;

    return true;
   },
    /*文件移除前,提示是否刪除*/
   beforeRemove(file,fileList){//delJar
    this.$confirm('此操作將永久刪除該文件, 是否繼續(xù)?', '提示', {
     confirmButtonText: '確定',
     cancelButtonText: '取消',
     type: 'warning'
    }).then(() => {
     this.$http.get('/aaaa/task/del?taskId='+this.taskId+'&name='+file.name).then(function(res) {
      ......
     });
    }).catch(() => {
     this.getJarList();
     return false;
    });
   },
   /*文件上傳,重寫文件上傳方法,action的路徑不會起作用*/
   myUpload(file){
    let fd = new FormData();
    fd.append('file',this.file);//傳文件
    fd.append('taskId',this.taskId);//傳其他參數(shù)
    // fd.append('filename',file.name);//傳其他參數(shù)
    this.$http.post('/aaaa/task/add',fd).then(function(res) {
     ....
    });
   },

name:"xxxx.jar"
status:"success"
uid:123456456

this.param={
  taskId:this.taskId
}

  @RequestMapping(value = "/add", produces = "multipart/form-data;charset=utf-8", method = RequestMethod.POST)
  public String addJar(int taskId, HttpServletRequest request) throws IOException, ServletException {
    ....
    //獲取文件
    Part part = request.getPart("file");// input的name值
    String dis = part.getHeader("Content-Disposition");
    // 獲取文件名--sdsf.jar
    String fna = dis.substring(dis.indexOf("filename=") + 10, dis.length() - 1);
    String fname = fna.substring(fna.lastIndexOf("\\") + 1, fna.length());// 有的瀏覽器獲取的是路徑+文件名
    // 若是文件名為空，說明此時沒有選擇文件，返回，文件上傳失敗，選擇文件
    if (fname.length() < 1) {
     //此時沒有選擇文件
    }
    ....
  }

imageUrl: '',

<el-form-item label="封面圖片" :required="true">
  <el-upload class="avatar-uploader" action="http://xxx.cn/xx/file/uploadImg/" name='photo' :show-file-list="false"
   :on-success="handleAvatarSuccess" :before-upload="beforeAvatarUpload">
   <img v-if="imageUrl" :src="imageUrl" class="avatar">
   <i v-else class="el-icon-plus avatar-uploader-icon"></i>
  </el-upload>
</el-form-item>

handleAvatarSuccess(res, file) {
    console.log(res)
    console.log(file)
    this.imageUrl = URL.createObjectURL(file.raw);
    console.log(this.imageUrl)
   },
   //驗證圖片格式
   beforeAvatarUpload(file) {
    const isJPG = file.type === 'image/jpeg';
    const isLt2M = file.size / 1024 / 1024 < 2;

    if (!isJPG) {
     this.$message.error('上傳頭像圖片只能是 JPG 格式!');
    }
    if (!isLt2M) {
     this.$message.error('上傳頭像圖片大小不能超過 2MB!');
    }
    return isJPG && isLt2M;
   },

/* 圖片上傳css */
 .avatar-uploader /deep/.el-upload {
  border: 1px dashed #d9d9d9;
  border-radius: 6px;
  cursor: pointer;
  position: relative;
  overflow: hidden;
 }

 .avatar-uploader .el-upload:hover {
  border-color: #409EFF;
 }

 .avatar-uploader-icon {
  font-size: 28px;
  color: #8c939d;
  width: 100px;
  height: 100px;
  line-height: 100px;
  text-align: center;
 }
 .avatar {
  width: 100px;
  height: 100px;
  display: block;
 }