猫鼬不返回带有findById的输出

我正在与获取MEAN应用程序一起学习nodejs和mongodb

我的系统规格是

ubuntu 16.04（64位）
节点v 6.1.0
npm v 3.8.6

“ mongodb”：“ ^ 2.1.18”，
“ mongoose”：“ ^ 4.4.16”，

到目前为止，我已经创建的模式，并通过终端使用MongoDB中添加集合中的条目db.locations.save()，并得到生成的文档_id用db.locations.find()。

终端中的db.locations.find（）。pretty（）返回以下输出

{
    "_id" : ObjectId("57428745e89f5c55e1d057dc"),
     // and many other path 
}

现在，当我在浏览器中打开/ api / locations / 57428745e89f5c55e1d057dc时，它既没有给出结果，也没有结束请求。与邮递员一起测试时，永久显示加载中。

甚至尝试使用错误的ID也会返回正确的错误

{“ message”：“在路径\” _ id \“”，“ name”：“ CastError”，“ kind”：“ ObjectId”，“ value”：“ 57428745e89f5c55e1d057dca”的值\“ 57428745e89f5c55e1d057dca \”的对ObjectId的转换失败， “ path”：“ _ id”}

并使用正确的ID

console.log(mongoose.Types.ObjectId.isValid(req.params.locationid));  // return true

甚至尝试过

findOne({"_id": mongoose.Types.ObjectId(req.params.locationid) })

但是没有结果

可能是什么问题？猫鼬中是否有任何bug或缺少任何内容？以下是我的基本文件以及所需的代码

loc8r / app.js

require('./app_api/models/db');
var routesApi = require('./app_api/routes/index');
app.use('/api', routesApi);

loc8r / app_api / models / db.js

var mongoose  = require( 'mongoose' );    
var mongoURI = 'mongodb://localhost/loc8r';    
var mongoDB = mongoose.createConnection(mongoURI);

mongoDB.on('connected', function (){
    console.log('mongoose connected to ' + mongoURI);
});

require('./locations');

loc8r / app_api / models / locations.js

var mongoose  = require( 'mongoose' );    
var openingTimeSchema = new mongoose.Schema({
days: {type: String, required: true},
opening: String,
closing: String,
closed: {type: Boolean, required: true}
});

var reviewSchema = new mongoose.Schema({
author: String,
rating: {type: Number, required: true, min: 0, max: 5},
reviewText: String,
createdOn: {type: Date, "default": Date.now}
});

var locationSchema = new mongoose.Schema({
    name: {type: String, required: true},
    address: String,
    rating: {type: Number, "default": 0, min: 0, max: 5},
    facilities: [String],
    coords: {type: [Number], index: '2dspehere'},
    openingTime: [openingTimeSchema],
    reviews: [reviewSchema]
});

mongoose.model('Location', locationSchema);

loc8r / app_api / router / index.js

var express = require('express');
var router = express.Router();
var ctrlLocations = require('../controllers/locations');

/* Locations pages */
router.get('/locations/:locationid', ctrlLocations.locationsReadOne);

loc8r / app_api / controllers / locations.js

var mongoose = require('mongoose');
var Loc = mongoose.model('Location');

module.exports.locationsReadOne =  function (req, res) {
    if(req.params && req.params.locationid) {            
        Loc
        .findById(req.params.locationid)
        .exec(function(err, location) {
            if(err) {
                sendJsonResponse(res, 404, err);
                return;
            }
            if (!location) {
                sendJsonResponse(res, 404, {"message": "locationid not found"});
                return;
            }
            sendJsonResponse(res, 200, location);
        });
    } else {
         sendJsonResponse(res, 200, {"message": "no location id in request"});
    }
}

var sendJsonResponse = function(res, status, content) {
    res.status(status);
    res.json(content);
};