Express错误处理中间件未触发致服务崩溃问题求助

你的路由处理器是async函数，内部抛出的错误会转化为未处理的Promise拒绝，Express无法自动将这类错误传递给自定义错误处理中间件，最终导致服务器崩溃。

方案一：手动捕获错误并传递给next #

修改路由处理器，添加next参数，用try/catch捕获错误后传递给错误中间件：

import express, { Request, Response, NextFunction } from "express";
import { body, validationResult } from "express-validator";

const router = express.Router();

router.post(
    "/lead",
    [
        body("email").isEmail().withMessage("Email must be valid"),
        body("name").notEmpty().withMessage("A name has to be provided"),
    ],
    async (req: Request, res: Response, next: NextFunction) => {
        try {
            const errors = validationResult(req);

            if (!errors.isEmpty()) {
                throw new Error("Invalid Email");
            }

            const { email, name } = req.body;

            console.log("Creating a user...");

            res.send({});
        } catch (err) {
            next(err); // 将错误传递给自定义错误处理中间件
        }
    }
);

export { router as leadRouter };

方案二：封装通用async错误处理包装函数 #

避免每个async路由都重复写try/catch，可以定义一个通用包装函数自动捕获错误：

import express, { Request, Response, NextFunction } from "express";
import { body, validationResult } from "express-validator";

const router = express.Router();

// 定义async错误处理包装函数
const asyncHandler = (fn: (req: Request, res: Response, next: NextFunction) => Promise<any>) => {
    return (req: Request, res: Response, next: NextFunction) => {
        fn(req, res, next).catch(next);
    };
};

router.post(
    "/lead",
    [
        body("email").isEmail().withMessage("Email must be valid"),
        body("name").notEmpty().withMessage("A name has to be provided"),
    ],
    asyncHandler(async (req: Request, res: Response) => {
        const errors = validationResult(req);

        if (!errors.isEmpty()) {
            throw new Error("Invalid Email");
        }

        const { email, name } = req.body;

        console.log("Creating a user...");

        res.send({});
    })
);

export { router as leadRouter };

方案三：直接返回express-validator验证错误（更贴合场景） #

既然已经使用express-validator，可以直接返回验证结果，无需手动抛错：

import express, { Request, Response } from "express";
import { body, validationResult } from "express-validator";

const router = express.Router();

router.post(
    "/lead",
    [
        body("email").isEmail().withMessage("Email must be valid"),
        body("name").notEmpty().withMessage("A name has to be provided"),
    ],
    async (req: Request, res: Response) => {
        const errors = validationResult(req);

        if (!errors.isEmpty()) {
            return res.status(400).send({ 
                message: "Something went wrong",
                details: errors.array() 
            });
        }

        const { email, name } = req.body;

        console.log("Creating a user...");

        res.send({});
    }
);

export { router as leadRouter };

Express的错误处理中间件仅能捕获同步代码错误，或通过next(err)主动传递的错误。对于async函数内部的错误，必须手动捕获后传递给next，或通过包装函数自动处理，否则会触发未处理的Promise拒绝，导致服务器崩溃。

内容的提问来源于stack exchange，提问作者Wagner Gauer