node.js – Mongodb错误：无法连接到[localhost：27017]

var express = require('express'),mongoose = require('mongoose');


var db = mongoose.connect('mongodb://localhost/bookAPI');

var Book = require('./models/bookmodel');

var app = express();

var port = process.env.PORT || 3002;


var bookRouter = express.Router();

bookRouter.route('/Books')
    .get(function(req,res){

        Book.find(function(err,books){
            if(err)
                console.log(err);
            else
                res.json(books);
        });
    });


app.use('/api',bookRouter);



app.get('/',function(req,res){
    res.send('welcome to my API!');
});

app.listen(port,function(){
    console.log('Gulp is running my app on  PORT: ' + port);
});

Bookmodel.js文件：

var mongoose = require('mongoose'),scheR_186_11845@a = mongoose.scheR_186_11845@a;

var bookmodel = new scheR_186_11845@a({
    title: {
        type: String
    },author: {type: String},genre: {type: String},read: {type: Boolean,default:falsE}
});

module.exports= mongoose.model('Book',bookmodel);

我的gulpfile是：

var gulp = require('gulp'),nodemon = require('gulp-nodemon');


gulp.task('default',function(){
    nodemon({
        script: 'app.js',ext: 'js',env: {
            PORT:8000
        },ignore: ['./node_modules/**']
    })
    .on('restart',function(){
        console.log('RestarTing');
    });
});

但是我一直收到错误：

Gulp is running my app on  PORT: 8000
events.js:85
      throw er; // Unhandled 'error' event
            ^
Error: Failed to connect to [localhost:27017]
  at null.<anonymous> (/Users/admin/Documents/NodeAndExpress/node_modules/mongoose/node_modules/mongodb/lib/mongodb/connection/server.js:549:74)

这非常令人沮丧,因为我非常密切地关注了Pluralsight课程.我已经安装了所有必要的npm软件包等.当我删除连接线时,它肯定是导致错误的mongoose连接.数据库尚未创建,但教师提到它应该自动创建(如果它尚不存在).

我尝试用mongod手动启动mongoose连接,但是我收到错误：

ERROR: dbpath (/data/db) does not exist.
 Create this directory or give exisTing directory in --dbpath.