MongoDB不会从nodejs应用中的mongodb中获取一些结果

我想通过mongoskin从mongodb读取一些数据。 但是，当我尝试调用localhost：3000 /任务时，nodejs抛出错误

在我的数据库'todo'中有一些项目在集合'任务'。 当我启动应用程序时，控制台中的结果工作正常。

任何人都可以看到我写错了什么？

消息消息：

500 TypeError: Cannot read property 'tasks' of undefined at exports.list (/Users/piet/Websites/privat/mongo/routes/tasks.js:7:8) at callbacks (/Users/piet/Websites/privat/mongo/node_modules/express/lib/router/index.js:164:37) at param (/Users/piet/Websites/privat/mongo/node_modules/express/lib/router/index.js:138:11) at pass (/Users/piet/Websites/privat/mongo/node_modules/express/lib/router/index.js:145:5) at Router._dispatch (/Users/piet/Websites/privat/mongo/node_modules/express/lib/router/index.js:173:5) at Object.router (/Users/piet/Websites/privat/mongo/node_modules/express/lib/router/index.js:33:10) at next (/Users/piet/Websites/privat/mongo/node_modules/express/node_modules/connect/lib/proto.js:193: 15) at Object.methodOverride [as handle] (/Users/piet/Websites/privat/mongo/node_modules/express/node_modules/connect/lib/middleware/me thodOverride.js:48:5) at next (/Users/piet/Websites/privat/mongo/node_modules/express/node_modules/connect/lib/proto.js:193: 15) at Object.urlencoded [as handle] (/Users/piet/Websites/privat/mongo/node_modules/express/node_modules/connect/lib/middleware/ur lencoded.js:49:37) 

我的app.js：

 var express = require('express'); var routes = require('./routes'); var tasks = require('./routes/tasks'); var http = require('http'); var path = require('path'); var mongo = require("mongoskin"); var db = mongo.db('localhost:27017/todo?auto_reconnect=true', { safe:true }) .collection('tasks') .find() .toArray(function(error, items){ console.log(items); }) var app = express(); app.set('port', process.env.PORT || 3000); app.set('views', path.join(__dirname, 'views')); app.set('view engine', 'jade'); app.use(express.favicon()); app.use(express.logger('dev')); app.use(express.json()); app.use(express.urlencoded()); app.use(express.methodOverride()); app.use(app.router); app.use(express.static(path.join(__dirname, 'public'))); if ('development' == app.get('env')) { app.use(express.errorHandler()); } app.get('/', routes.index); app.get('/tasks', tasks.list); http.createServer(app).listen(app.get('port'), function(){ console.log('Express server listening on port ' + app.get('port')); }); 

/routes/tasks.js下的路由文件

 exports.list = function(req, res, next){ req.db.tasks.find({ completed: false }).toArray(function(error, tasks){ res.render('tasks', { title: "ToDo list", name: tasks = tasks || [] }) }) }; 

Answer 1

使用28017作为端口号。 你可以检查你在“req.db”中得到了什么。 Mayb这是不确定的。

Answer 2

您将需要一个中间件来将收集对象连接到您的请求：

 var db = mongo.db('localhost:27017/todo?auto_reconnect=true'); var tasks = db.collection('tasks'); ... app.use(function(req, res, next) { req.db = { tasks : tasks }; // this exposes the collection as `req.db.tasks` // to your route handlers next(); }); app.use(app.router); ... 

Answer 3

在您的routes / task.js中，req是Express.js的请求对象。 它没有“db”句柄，这就是为什么你会得到错误：

 500 TypeError: Cannot read property 'tasks' of undefined 

在app.js中，这是获取数据库句柄的不正确方法：

 var mongo = require("mongoskin"); var db = mongo.db('localhost:27017/todo?auto_reconnect=true', { safe:true }) .collection('tasks') .find() .toArray(function(error, items){ console.log(items); }); 

数据库代码应该移动到一个单独的模块（例如dbConnection.js），以便每次需要db句柄时，您只需要这样做：

 var db = require('./dbConnection').getDb(); 

routes / task.js需要获取数据库句柄来进行数据库调用。 所以这里是你修改的app.js，routes / task.js和新的dbConnection.js文件：

dbConnection.js：

 var open = function() { return require('mongoskin').db('localhost:27017/todo?auto_reconnect=true', {safe: true, strict: false} ); }; var db = open(); var dbConnection = { getDb: function() { if (!db) { db = open(); } return db; } }; module.exports = dbConnection; 

路线/ task.js：

 var db = require('../dbConnection').getDb(); exports.list = function(req, res, next){ var tasksCollection = db.collection('tasks'); tasksCollection.find({ completed: false }).toArray(function(error, tasks){ res.render('tasks', { title: "ToDo list", name: (tasks || []) }); }); }; 

app.js：

 var express = require('express'); var routes = require('./routes'); var tasks = require('./routes/tasks'); var http = require('http'); var path = require('path'); var app = express(); app.set('port', process.env.PORT || 3000); app.set('views', path.join(__dirname, 'views')); app.set('view engine', 'jade'); app.use(express.favicon()); app.use(express.logger('dev')); app.use(express.json()); app.use(express.urlencoded()); app.use(express.methodOverride()); app.use(app.router); app.use(express.static(path.join(__dirname, 'public'))); if ('development' == app.get('env')) { app.use(express.errorHandler()); } app.get('/', routes.index); app.get('/tasks', tasks.list); http.createServer(app).listen(app.get('port'), function(){ console.log('Express server listening on port ' + app.get('port')); });