Express+Mongoose中/hello路由出现ObjectId转换错误求助

使用本地MongoDB、Node.js、Express和Mongoose开发，其余路由均正常，唯独GET方法的/products/hello路由出现如下错误：

{
    "stringValue": "\"hello\"",
    "valueType": "string",
    "kind": "ObjectId",
    "value": "hello",
    "path": "_id",
    "reason": {},
    "name": "CastError",
    "message": "Cast to ObjectId failed for value \"hello\" (type string) at path \"_id\" for model \"product\""
}

将该路由改为POST方法可正常工作，改回GET方法仍报错，即使删除该路由错误依然存在。

相关代码 #

index.js

import mongoose from "mongoose";
import  express, { json }  from "express";
import 'dotenv/config'
import productRouter from './routes/productR.js' 

const app = express()

const connectionToDB = async () => {
  try {
    await mongoose.connect('mongodb://127.0.0.1:27017/testingDB')
    console.log('Connected to mongoDB');
  } catch (error) {
    console.log(error);
  }
}

app.use(json())
app.use('/products', productRouter)

app.listen(process.env.PORT, ()=>{
    connectionToDB()
    console.log('Server in up at '+ process.env.PORT);
})

product模型（productM.js）

import mongoose from "mongoose";

const productSchema = new mongoose.Schema({
    name:{
        type:String
    },
    brand:{
        type: String,
    },
    size:{
        type:[String],
    },
    desc:{
        type:String
    },
    price:{
        type:Number
    }, 
    category:{
        type:String
    },
    picture:{
        type:String
    }
})

export default mongoose.model('product',productSchema)

product路由（productR.js）

import express  from "express";
import { addProduct, deleteProduct, getProduct, getProducts, updateProduct } from "../controllers/productC.js";

const router = express.Router()

router.post('/',addProduct)
router.put('/:id',updateProduct)
router.delete('/:id',deleteProduct)
router.get('/:id',getProduct)
router.get('/',getProducts)

router.get("/hello",(req, res)=>{
    res.json('5464')
})

export default router;

product控制器（productC.js）

import Product from '../models/productM.js'

export const addProduct = async (req, res)=>{
    const newProduct = Product(req.body)
    try {
        const savedProduct = await newProduct.save()
        res.status(200).json(savedProduct)
    } catch (error) {
        res.status(500).json(error)
    }
}

export const updateProduct = async (req, res) => {
    try {
        const updatedProduct = await Product.findById(req.params.id)
        if(req.body.name) { updatedProduct.name = req.body.name}
        if(req.body.brand) { updatedProduct.brand = req.body.brand}
        if(req.body.size) { updatedProduct.size =(req.body.size)}
        if(req.body.desc) { updatedProduct.desc = req.body.desc}
        if(req.body.price) { updatedProduct.price = req.body.price}
        if(req.body.picture) { updatedProduct.picture = req.body.picture}
        if(req.body.category) { updatedProduct.category = req.body.category}
        await updatedProduct.save()
        res.status(200).json(updatedProduct)
    } catch (error) {
        res.status(500).json(error)
    }
}

export const deleteProduct = async (req, res) => {
    
    try {
        await Product.findByIdAndDelete(req.params.id)
        res.status(200).json(`The product (${req.params.id}) has been deleted`)
    } catch (error) {
        res.status(500).json(error)
    }
}

export const getProduct = async (req, res) => {
    const productID = req.params.id
    try {
        const foundProduct = await Product.findById(productID)
        res.status(200).json(foundProduct)
    } catch (error) {
        res.status(500).json(error)
    }
}

export const getProducts = async (req, res) => {
    const {min,max, ...others} = req.query
    const name = req.query.name || "";
    const category = req.query.category || "";
    const brand = req.query.brand || "";
    console.log(name);
    try {
        const foundProducts = await Product.find({$and:[
            { price:{$gte:parseInt(min) || 1, $lte:parseInt(max) || 9999}},
            {name: {$regex: `${name}` || "" , $options: 'i' }},
            {brand: {$regex: `${brand}` || "" , $options: 'i' }},
            {category: {$regex: `${category}` || "" , $options: 'i' }}
        ]})
        res.status(200).json(foundProducts)
    } catch (error) {
        res.status(500).json(error)
    }
}

原因 #

Express路由按定义顺序匹配。当前代码中router.get('/:id', getProduct)在router.get('/hello', ...)之前，请求/products/hello时，Express会把hello当作:id参数传入getProduct控制器。Mongoose的findById方法会尝试将这个字符串转换为MongoDB ObjectId，而hello不是合法的ObjectId格式，因此抛出CastError。

改为POST方法能正常工作，是因为POST路由中没有定义/:id，不存在匹配冲突；删除/hello路由后错误依然存在，是因为/products/hello仍会被/:id路由捕获，触发同样的转换错误。

解决方案 #

调整路由顺序，将静态路由（如/hello）放在动态参数路由（如/:id）之前，让Express优先匹配静态路由：

修改后的product路由代码：

import express  from "express";
import { addProduct, deleteProduct, getProduct, getProducts, updateProduct } from "../controllers/productC.js";

const router = express.Router()

router.post('/',addProduct)
router.put('/:id',updateProduct)
router.delete('/:id',deleteProduct)
// 静态路由提前
router.get("/hello",(req, res)=>{
    res.json('5464')
})
router.get('/:id',getProduct)
router.get('/',getProducts)

export default router;

额外优化建议 #

在getProduct控制器中提前校验参数是否为合法ObjectId，避免Mongoose抛出异常：

import mongoose from 'mongoose';
import Product from '../models/productM.js'

export const getProduct = async (req, res) => {
    const productID = req.params.id
    // 校验ObjectId合法性
    if(!mongoose.Types.ObjectId.isValid(productID)){
        return res.status(400).json({message: '无效的产品ID格式'})
    }
    try {
        const foundProduct = await Product.findById(productID)
        if(!foundProduct){
            return res.status(404).json({message: '未找到该产品'})
        }
        res.status(200).json(foundProduct)
    } catch (error) {
        res.status(500).json(error)
    }
}

内容的提问来源于stack exchange，提问作者Mohammed Nacer Eddine Meddour