NodeJS + MongoDB：使用 findOne() 从集合中获取数据
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NodeJS + MongoDB: Getting data from collection with findOne ()
提问by f1nn
I have a collection "companies" with several objects. Every object has "_id" parameter. I'm trying to get this parameter from db:
我有一个包含多个对象的“公司”集合。每个对象都有“_id”参数。我正在尝试从 db 获取此参数：
app.get('/companies/:id',function(req,res){
db.collection("companies",function(err,collection){
console.log(req.params.id);
collection.findOne({_id: req.params.id},function(err, doc) {
if (doc){
console.log(doc._id);
} else {
console.log('no data for this company');
}
});
});
});
So, I request companies/4fcfd7f246e1464d05000001 (4fcfd7f246e1464d05000001 is _id-parma of a object I need) and findOne returns nothing, that' why console.log('no data for this company'); executes.
因此，我请求公司/4fcfd7f246e1464d05000001（4fcfd7f246e1464d05000001 是我需要的对象的 _id-parma）并且 findOne 什么都不返回，这就是为什么 console.log('no data for this company'); 执行。
I'm absolutely sure that I have an object with _id="4fcfd7f246e1464d05000001". What I'm doing wrong? Thanks!
我绝对确定我有一个 _id="4fcfd7f246e1464d05000001" 的对象。我做错了什么？谢谢！
However, I've just noticed that id is not a typical string field. That's what mViewer shows:
但是，我刚刚注意到 id 不是典型的字符串字段。这就是 mViewer 显示的内容：
"_id": {
"$oid": "4fcfd7f246e1464d05000001"
},
Seems to be strange a bit...
好像有点奇怪……
回答by Adam Comerford
You need to construct the ObjectID and not pass it in as a string. Something like this should work:
您需要构造 ObjectID 而不是将其作为字符串传入。这样的事情应该工作：
var BSON = require('mongodb').BSONPure;
var obj_id = BSON.ObjectID.createFromHexString("4fcfd7f246e1464d05000001");
Then, try using that in your find/findOne.
然后，尝试在您的 find/findOne 中使用它。
Edit: As pointed out by Ohadin the comments (thanks Ohad!), you can also use:
编辑：正如Ohad在评论中指出的（感谢 Ohad！），您还可以使用：
new require('mongodb').ObjectID(req.params.id)
Instead of createFromHexStringas outlined above.
而不是createFromHexString如上所述。
回答by Aleksei Zabrodskii
That's because _idfield in mongo isn't of stringtype (as your req.params.id). As suggested in other answers, you should explicitly convert it.
那是因为_idmongo 中的字段不是string类型（如您的req.params.id）。正如其他答案中所建议的那样，您应该明确转换它。
Try mongoskin, you could use it like node-mongodb-native driver, but with some sugar. For example:
试试mongoskin，你可以像 node-mongodb-native 驱动程序一样使用它，但要加点糖。例如：
// connect easier
var db = require('mongoskin').mongo.db('localhost:27017/testdb?auto_reconnect');
// collections
var companies = db.collection('companies');
// create object IDs
var oid = db.companies.id(req.params.id);
// some nice functions…
companies.findById();
//… and bindings
db.bind('companies', {
top10: function(callback) {
this.find({}, {limit: 10, sort: [['rating', -1]]).toArray(callback);
}
});
db.companies.top10(printTop10);
回答by darren
You can use findById()which will take care of the id conversion for you.
您可以使用findById()which 将为您处理 id 转换。
company = Company.findById(req.params.id, function(err, company) {
//////////
});
回答by matteo_dm
In case these didn't work for you, this worked for me for accessing a blog post:
如果这些对您不起作用，这对我访问博客文章有用：
const getSinglePost = async (req, res) => {
let id = req.params.id;
var ObjectId = require('mongodb').ObjectId;
const db = await client.db('CMS');
const data = await db.collection("posts").findOne({ _id: ObjectId(id) })
if (data) {
res.status(200).send(data)
} else res.status(400).send({ message: "no post found" })
}
