[英]My api code retrieves an empty data array from mongodb while the code works well on mongodb playground
我的 mongodb 数据库包含一组用户,每个用户都有一系列商店,每个商店都有一系列产品。 这是我的收藏结构的简化版本:
[
{
"_id": "60e66b70da2439232e330415",
"name": "User1 Name",
"shops": [
{
"_id": "60e7c9e2be0d8f03544a03b8",
"shopName": "User1 Shop1 Name",
"products": [
{
"_id": "60e9e9e8105d6021a2e91535",
"title": "User1 Shop1 Product1 Title"
},
{
"_id": "60e9f4a0105d6021a2e91536",
"title": "User1 Shop1 Product2 Title"
}
]
},
{
"_id": "60e8e8c00f3986577cb968c9",
"shopName": "User1 Shop2 Name",
"products": [
{
"_id": "60e9f4fe105d6021a2e91537",
"title": "User1 Shop2 Product1 Title"
},
{
"_id": "60e9f515105d6021a2e91538",
"title": "User1 Shop2 Product2 Title"
}
]
}
]
},
{
"_id": "60e66b93da2439232e330416",
"name": "User2 Name",
"shops": [
{
"_id": "60e69698e76cad44e49e1fc8",
"shopName": "User2 Shop1 Name",
"products": [
{
"_id": "60e9f588105d6021a2e91539",
"title": "User2 Shop1 Product1 Title"
},
{
"_id": "60e9f59c105d6021a2e9153a",
"title": "User2 Shop1 Product2 Title"
}
]
},
{
"_id": "60e902b441e9df63c7fbcb49",
"shopName": "User2 Shop2 Name",
"products": [
{
"_id": "60e9f5c9105d6021a2e9153b",
"title": "User2 Shop2 Product1 Title"
},
{
"_id": "60e9f5de105d6021a2e9153c",
"title": "User2 Shop2 Product2 Title"
}
]
}
]
}
]
我有一个像.../api/products/60e9f5de105d6021a2e9153c
这样的 api 端点。 此端点包含一个参数,即 productId。 我有以下两个代码来从我的 mongodb 集合中检索产品数据,但检索到的数组为空。
我的端点代码:
app.get("/api/products/:productId", (req,res)=>{
let productId = req.params.productId;
myData.getProductByProductId(productId)
.then(products => res.json(products))
.catch(err => res.json({"message": err}));
});
我的数据服务代码:
getProductByProductId: function (productId) {
return new Promise((resolve, reject) => {
User.aggregate([
{
$match: {
"shops.products._id": productId
}
},
{
"$unwind": "$shops"
},
{
"$unwind": "$shops.products"
},
{
$match: {
"shops.products._id": productId
}
},
{
$project: {
"_id": "$shops.products._id",
"title": "$shops.products.title"
}
}
])
.exec().then(products => {
resolve(products)
}).catch(err => {
reject(err);
});
});
}
聚合代码在这个操场上运行良好,但在我的网络应用程序代码中检索一个空数组。
结果证明 ObjectId 的转换似乎是问题所在。 我们需要使用mongoose.Types.ObjectId
API 代码如下所示
getProductByProductId: function (productId) {
return new Promise((resolve, reject) => {
User.aggregate([
{
$match: {
"shops.products._id": mongoose.Types.ObjectId(productId)
}
},
{
"$unwind": "$shops"
},
{
"$unwind": "$shops.products"
},
{
$match: {
"shops.products._id": mongoose.Types.ObjectId(productId)
}
},
{
$project: {
"_id": "$shops.products._id",
"title": "$shops.products.title"
}
}
])
.then(products => {
resolve(products)
}).catch(err => {
reject(err);
});
});
}
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