Strapi-Mongodb从upload_file集合返回空数组

Question

upload.js文件：

const router = require('express').Router();
let Upload_file = require('../models/upload.model');

router.route('/upload_file').get((req, res) => {
    Upload_file.find()
        .then(upload_file => res.json(upload_file))
        .catch(err => res.status(400).json('Error: ' + err));
});

module.exports = router;

upload.model.js

const mongoose = require('mongoose');

const Schema = mongoose.Schema;

const upload_fileSchema = new Schema({
    upload_file: {
        _id: String,
        name: String,
        url: String,
        mime: String
    },
}, {
    timestamps: true,
});

const Upload_file = mongoose.model('Upload_file', upload_fileSchema);

module.exports = Upload_file;

其他集合工作完美，但是当我想获取json文件时，数组为空，但是集合中有多个文档。