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javascript - 未处理的承诺拒绝和 ERR_HTTP_HEADERS_SENT

问题描述

我正在尝试使用 node express 和 mysql 创建一个 rest api 服务器，请求的结构是这样的：

这是路线

router.get('/api/courseDetails/:id', async (req, res) => {
    try {
        let levels = await db.levelsByCourseId(req.params.id)
        res.sendStatus(200).json(levels)
    } catch (e) {
        console.log(e)
        res.sendStatus(500)
    }
})

这是查询：

requests.levelsByCourseId = (id) => {
    let query = "select * from levels where parent_course_id="+id+" and visibility>0"
    return new Promise((resolve, reject) => {
        pool.query(query,(err, results) => {
            if (err) {
                return reject(err)
            }
            return resolve(results)
        })
    })
}

我也将此结构用于其他没有错误的请求，但这给了我这个错误：

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (_http_outgoing.js:485:11)
    at ServerResponse.header (C:\Users\giuse\VScodeProjects\noderest-tutorial-server\node_modules\express\lib\response.js:771:10)
    at ServerResponse.json (C:\Users\giuse\VScodeProjects\noderest-tutorial-server\node_modules\express\lib\response.js:264:10)
    at C:\Users\giuse\VScodeProjects\noderest-tutorial-server\server\routes\index.js:47:29
    at processTicksAndRejections (internal/process/task_queues.js:93:5) {
  code: 'ERR_HTTP_HEADERS_SENT'
}
(node:15588) UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (_http_outgoing.js:485:11)
    at ServerResponse.header (C:\Users\giuse\VScodeProjects\noderest-tutorial-server\node_modules\express\lib\response.js:771:10)
    at ServerResponse.contentType (C:\Users\giuse\VScodeProjects\noderest-tutorial-server\node_modules\express\lib\response.js:599:15)
    at ServerResponse.sendStatus (C:\Users\giuse\VScodeProjects\noderest-tutorial-server\node_modules\express\lib\response.js:357:8)
    at C:\Users\giuse\VScodeProjects\noderest-tutorial-server\server\routes\index.js:50:13
    at processTicksAndRejections (internal/process/task_queues.js:93:5)
(node:15588) 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:15588) [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.

任何人都可以帮助我吗？谢谢你

编辑：在客户端我有一个承诺而不是一些数据（它在承诺内）

Promise {<pending>}
__proto__: Promise
[[PromiseState]]: "fulfilled"
[[PromiseResult]]: "OK"

和 axios 代码：

 static async getCourseDetails(id) {
        try {
            const data = await axios.get(basepath + '/api/courseDetails/' + id)
            return data.data
        } catch (error) {
            throw error;
        }
    }

标签： javascriptnode.js

解决方案

在将结果发送给客户端之前，您使用了错误的方法来设置状态。它应该是这样的：

res.status(200).json(levels)

打电话给setStatus你res.status(200).send('OK')，然后你打电话json也设置状态 200 并将结果作为 JSON 发送。

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