node.js - 在此代码中，两条路线的逻辑相同，但它们的行为有所不同

// @route   GET api/profile/handle/:handle
// @desc    Get profile by handle
// @access  Public

router.get('/handle/:handle', (req, res) => {
    const errors = {};

    Profile.findOne({ handle: req.params.handle })
        .populate('user', ['name', 'avatar'])
        .then(profile => {
            //console.log('profile1 ' + profile);
            if (!profile) {
                errors.noprofile = 'There is no profile for this user for handle route (from then block)';
                res.status(404).json(errors);
            }
            res.json(profile);
        })
        .catch(err => res.status(404).json({ profile: 'There is no profile for this user for handle route (from error block)' }));

});

// @route   GET api/profile/user/:user_id
// @desc    Get profile by user ID
// @access  Public

router.get('/user/:user_id', (req, res) => {
    const errors = {};

    Profile.findOne({ user: req.params.user_id })
        .populate('user', ['name', 'avatar'])
        .then(profile => {
            // console.log('profile not found by userid');
            //console.log('profile2 ' + profile);
            if (!profile) {
                errors.noprofile = 'There is no profile for this user for user_id route (from then block)';
                res.status(404).json(errors);
            }
            res.json(profile);
        })
        .catch(err => res.status(404).json({ profile: 'There is no profile for this user for user_id route (from error block)',
err: err }));
});

我有以上两条路线。第一个是使用handle（用户名）从dB搜索用户，第二个是使用dB本身创建的user_id搜索。当我使用错误的句柄请求第一条路线时，then（）块将被执行，并且得到以下响应：

{
    "noprofile": "There is no profile for this user for handle route (from then block)"
}

但是在第二条路线（通过user_id搜索）中，当我输入错误的user_id时，catch块被执行，并且得到以下响应：

{
    "profile": "There is no profile for this user for user_id route (from error block)",
    "err": {
        "message": "Cast to ObjectId failed for value \"5cb0ec06d1d6f93c20874427rhdh\" at path \"user\" for model \"profile\"",
        "name": "CastError",
        "stringValue": "\"5cb0ec06d1d6f93c20874427rhdh\"",
        "kind": "ObjectId",
        "value": "5cb0ec06d1d6f93c20874427rhdh",
        "path": "user"
    }
}

两条路线的逻辑相同，但是它们的响应方式不同。这背后的原因是什么？？？

如果要查看Profile模式，则为：

const ProfileSchema = new Schema({
    user: {
        type: Schema.Types.ObjectId,
        ref: 'users'
    },
    handle: {
        type: String,
        required: true,
        max: 40
    },
    company: {
        type: String
    },
   ....
....
.....
});

请求错误的句柄时，我也收到警告：

(node:16996) UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (_http_outgoing.js:470:11)
    at ServerResponse.header (H:\MERN Stack Course\devConnector\node_modules\express\lib\response.js:767:10)
    at ServerResponse.send (H:\MERN Stack Course\devConnector\node_modules\express\lib\response.js:170:12)
    at ServerResponse.json (H:\MERN Stack Course\devConnector\node_modules\express\lib\response.js:267:15)
    at Profile.findOne.populate.then.catch.err (H:\MERN Stack Course\devConnector\routes\api\profile.js:75:39)
    at process._tickCallback (internal/process/next_tick.js:68:7)
(node:16996) 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(). (rejection id: 1)
(node:16996) [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.

最佳答案

检查错误消息

"message": "Cast to ObjectId failed for value \"5cb0ec06d1d6f93c20874427rhdh\" at path \"user\" for model \"profile\""

user字段是mongodb类型ObjectId，而您要提供String，而handle是String类型

如果是handle查询，则没有错误，只有db中没有条目。

您可以像mongoose.Types.ObjectId(req.params.user_id)一样修复它。 More here

另外，您的代码也有问题。 （执行不会在您认为停止的地方停止，并且您会遇到无法处理的承诺拒绝）

.then(profile => {
  //console.log('profile1 ' + profile);
  if (!profile) { // <--- if true
    errors.noprofile = 'There is no profile for this user for handle route (from then block)';
    res.status(404).json(errors); // <-- executes
  }
  res.json(profile); // <--- always executes within then callback
})

如果此检查if (!profile)评估为true，则将执行res.status(404).json(errors)。然后执行下一个res.json(profile)。

在您的代码中，总是在没有错误的情况下执行res.json(profile)。您可以通过使用return停止执行或if..else进行纠正，例如：

return res.status(404).json(errors);

// or
if (!profile) {
  errors.noprofile = 'There is no profile for this user for handle route (from then block)';
  res.status(404).json(errors);
} else {
  res.json(profile);
}