NestJS/Express 错误 [ERR_HTTP_HEADERS_SENT]：将标头发送到客户端后无法设置标头答案

【问题标题】：NestJS/Express Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the clientNestJS/Express 错误 [ERR_HTTP_HEADERS_SENT]：将标头发送到客户端后无法设置标头
【发布时间】：2022-11-30 13:41:40
【问题描述】：

有时我的服务器（嵌套) 因以下堆栈而崩溃：

node:internal/errors:464
    ErrorCaptureStackTrace(err);
    ^
Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at new NodeError (node:internal/errors:371:5)
    at ServerResponse.setHeader (node:_http_outgoing:576:11)
    at ServerResponse.header (/home/workspace/node_modules/express/lib/response.js:771:10)
    at ServerResponse.send (/home/workspace/node_modules/express/lib/response.js:170:12)
    at ServerResponse.json (/home/workspace/node_modules/express/lib/response.js:267:15)
    at ExpressAdapter.reply (/home/workspace/node_modules/@nestjs/platform-express/adapters/express-adapter.js:24:57)
    at ExceptionsHandler.handleUnknownError (/home/workspace/node_modules/@nestjs/core/exceptions/base-exception-filter.js:33:24)
    at ExceptionsHandler.catch (/home/workspace/node_modules/@nestjs/core/exceptions/base-exception-filter.js:17:25)
    at ExceptionsHandler.next (/home/workspace/node_modules/@nestjs/core/exceptions/exceptions-handler.js:16:20)
    at /home/workspace/node_modules/@nestjs/core/router/router-proxy.js:24:35
    at Layer.handle_error (/home/workspace/node_modules/express/lib/router/layer.js:71:5)
    at trim_prefix (/home/workspace/node_modules/express/lib/router/index.js:315:13)
    at /home/workspace/node_modules/express/lib/router/index.js:284:7
    at Function.process_params (/home/workspace/node_modules/express/lib/router/index.js:335:12)
    at next (/home/workspace/node_modules/express/lib/router/index.js:275:10)
    at Layer.handle_error (/home/workspace/node_modules/express/lib/router/layer.js:67:12) {
  code: 'ERR_HTTP_HEADERS_SENT'
}

我试图用我在类似 SO 上看到的一些建议（比如 here 或 here）来修复它，但它仍然发生。

使用的依赖项：

"@nestjs/common": "^7.6.12",
"@nestjs/config": "^0.6.3",
"@nestjs/core": "^7.6.12",
"@nestjs/jwt": "^7.2.0",
"@nestjs/mongoose": "^7.2.3",
"@nestjs/passport": "^7.1.5",
"@nestjs/platform-express": "^7.6.12",
"@nestjs/platform-socket.io": "^7.6.12",
"@nestjs/platform-ws": "^7.6.12",
"@nestjs/schedule": "^0.4.3",
"@nestjs/websockets": "^7.6.12",
"@types/string-similarity": "^4.0.0",
"bcrypt": "^5.0.1",
"class-transformer": "^0.2.3",
"class-validator": "^0.11.1",
"dotenv": "^10.0.0",
"express-useragent": "^1.0.15",
"mongodb": "^3.5.5",
"mongoose": "^5.9.7",
"nanoid": "^3.1.12",
"nestjs-i18n": "^8.1.0",
"nestjs-stripe": "^0.4.1",
"nodemailer": "^6.4.6",
"passport": "^0.4.1",
"passport-jwt": "^4.0.0",
"passport-local": "^1.0.0",
"path": "^0.12.7",
"reflect-metadata": "^0.1.13",
"rimraf": "^3.0.0",
"rxjs": "^6.5.3",
"string-similarity": "^4.0.4",
"stripe": "^8.39.0",
"typeorm": "^0.2.24"

可能有问题的代码：

应用控制器:

@Controller()
export class AppController {

    @Get()
    root(@Res() response): void {
        return response.sendFile(path.resolve(__dirname+'/../gui/index.html'));
    }

}

应用中间件:

@Injectable()
export class AppMiddleware implements NestMiddleware {

    use(req: Request, res: Response, next: Function) {
        const url = req.originalUrl;
        if (url.indexOf('api') === 1) {
            // it starts with /api --> continue with execution
            return next();
        } else if (allowedExt.filter(ext => url.indexOf(ext) > 0).length > 0) {
            // it has a file extension --> resolve the file
            return res.sendFile(path.resolve(__dirname + `/../gui/${url}`), err => {
                // Error: redirect to index.html
                if (err) {
                    return res.sendFile(path.resolve(__dirname + '/../gui/index.html'));
                }
            });
        } else {
            // in all other cases, redirect to the index.html
            return res.sendFile(path.resolve(__dirname + '/../gui/index.html'));
        }
    }

}

【问题讨论】：

标签： express nestjs

【解决方案1】：

在你的AppMiddleware：

return res.sendFile(path.resolve(__dirname + `/../gui/${url}`), err => {
    // Error: redirect to index.html
    if (err) {
        return res.sendFile(path.resolve(__dirname + '/../gui/index.html'));
    }
});

这可能是原因。你的 response 在 sendFile 之后结束，即使会出现错误，所以你不应该在回调中调用它。

【讨论】：