models：

    1. const mongoose = require("mongoose");
    2. //1.连接本地数据库
    3. var mongodb = mongoose.createConnection( 'mongodb://127.0.0.1:27017/movies', {useNewUrlParser: true});
    4. var Schema = mongoose.Schema;
    6. module.exports = {
    7.     mongodb,
    8.     Schema
    9. };
    1. const {mongodb,Schema} = require("./baseDB/db-movies");
    2. //2.在本地定义一个Schema和远程数据库的字段映射
    3. var MovieSchema =new Schema({
    4.     pic:String,
    5.     title:String,
    6.     raiting:String,
    7.     slogo:String,
    8.     evaluate:String,
    9.     labels:Array
    10. });
    11. // 3.创建数据模型，操作数据库  table是需要访问的集合名
    12. function MovieModel(table){
    13.     return mongodb.model(table,MovieSchema,table);  //是我们获取的数据库里叫table（变量）的那张表
    14. }
    15. module.exports = MovieModel;

    在路由中使用：

    1. const router = require("koa-router")();
    2. const MovieModel = require("../../models/movie");
    3. router.get("/api/movie",async ctx=>{
    4.     let {m} = ctx.query;
    5.     var data = await MovieModel(m).find().sort({rating:-1});
    6.     ctx.body = {
    7.         code:200,
    8.         res:data,
    9.         request:"GET /api/top250"
    10.     }
    11. })
    12. module.exports = router;