Node 和 Express 中未处理的 promise 错误

Question

我正在使用 NodeJS、ExpressJS 和 Mongoose 制作 CRUD API，在执行以下代码时，第 29 行出现 UnhandledPromiseRejectionWarning 错误。尽管有一个 try-catch 块。

代码：

const express = require('express');
const app = express();
const port = process.env.PORT || 3000;
require('../src/db/conn.js');
const MensRanking = require('../src/models/mens.js');
app.use(express.json());
app.get('/', async (req, res) =>{
    res.send("<h1>Hello World!</h1>");
})

app.post('/mens', async (req, res) =>{
    try{
        const addingMensRecords = new MensRanking(req.body);
        console.log(req.body);
        const insert = await addingMensRecords.save();
        res.sendStatus(201).send(insert);
    }
    catch(e){
        res.sendStatus(400).send(e);
    }
})  

app.get('/mens', async (req, res) =>{
    try{
        const getMens = await MensRanking.find({});
        res.sendStatus(201).send(getMens);
    }
    catch(e){
        res.sendStatus(400).send(e);
    }
})

app.listen(port,()=>{
    console.log(`\nlistening at http://127.0.0.1:${port}\n`);
})

错误：

(node:20016) UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (_http_outgoing.js:518:11)
    at ServerResponse.header (D:\projects\rest-api-sections\rest-tute\node_modules\express\lib\response.js:771:10)
    at ServerResponse.contentType (D:\projects\rest-api-sections\rest-tute\node_modules\express\lib\response.js:599:15)
    at ServerResponse.sendStatus (D:\projects\rest-api-sections\rest-tute\node_modules\express\lib\response.js:357:8)
    at D:\projects\rest-api-sections\rest-tute\src\app.js:29:13
    at processTicksAndRejections (internal/process/task_queues.js:97:5)
(node:20016) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:20016) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Here is the complete code repository

Answer 1

您应该使用res.status 而不是sendStatus

Difference between response.status() vs. response.sendStatus() in express

const express = require('express');
const app = express();
const port = process.env.PORT || 3000;
require('../src/db/conn.js');
const MensRanking = require('../src/models/mens.js');
app.use(express.json());
app.get('/', async (req, res) => {
  res.send('<h1>Hello World!</h1>');
});

app.post('/mens', async (req, res) => {
  try {
    const addingMensRecords = new MensRanking(req.body);
    console.log(req.body);
    const insert = await addingMensRecords.save();
    res.status(201).send(insert);
  }
  catch (e) {
    res.status(400).send(e);
  }
});

app.get('/mens', async (req, res) => {
  try {
    const getMens = await MensRanking.find({});
    res.status(201).send(getMens);
  }
  catch (e) {
    res.status(400).send(e);
  }
});

app.listen(port, () => {
  console.log(`\nlistening at http://127.0.0.1:${port}\n`);
});

Answer 2

您正在使用 epxress.js 的 sendStatus 函数，因为它会立即将特定分配的代码发送到响应对象，该对象在设置数据之前触发响应，因此当您的 send 函数被调用时，响应对象已经发送，因此错误：

标头发送到客户端后无法设置

相反，当您需要设置 HTTP 响应代码以及数据时使用它

res.status(RESPONSE_CODE).send(DATA)

Answer 3

在这种情况下有两个有问题的函数我只强调一个，因为它们有相同的错误：

app.post('/mens', async (req, res) =>{
try{
    const addingMensRecords = new MensRanking(req.body);
    console.log(req.body);
    const insert = await addingMensRecords.save();
    res.sendStatus(201).send(insert);
}
catch(e){
    res.sendStatus(400).send(e);
}})  

1. 您已经在 try-block 中使用 res.sendStatus(201) 发送了响应，并尝试使用 .send(insert) 再次发送 -> 引发异常
2. 之后，您再次使用 res.sendStatus(400).send(e); 执行相同的错误；

下面的代码应该能达到你想要的效果：

app.post('/mens', async (req, res) =>{
try{
    const addingMensRecords = new MensRanking(req.body);
    console.log(req.body);
    const insert = await addingMensRecords.save();
    res.status(201).send(insert);
}
catch(e){
    res.status(400).send(e);
}})