Node Cors捕获中间件回调错误 [英] Node cors catch middleware callback error

问题描述

我有以下代码使用express和npm cors插件来检查原始标头并允许访问

I have the following code to check the origin header and allow access, using express and the npm cors plugin

const app = express();
const cors = require('cors')
var corsOptions = {
    origin: function (origin: any, callback: any) {
        if (!origin || whitelist.indexOf(origin) !== -1) {
            callback(null, true)
        } else {
            callback(new Error('Not allowed by CORS'))
        }
    }
}
app.use(cors(corsOptions));

现在，我想知道是否有办法捕获新错误回调？

Now I wonder if there is way to catch the "new Error" callback?

并发回400个http状态？

And send back a 400 http status?

谢谢！

推荐答案

是的，这在Express文档中的错误处理。

Yes, this is explained in the Express docs under Error Handling.

Express带有内置的错误处理程序，可以处理在应用程式。该默认的错误处理中间件功能已添加到中间件功能栈的末尾。

Express comes with a built-in error handler that takes care of any errors that might be encountered in the app. This default error-handling middleware function is added at the end of the middleware function stack.

如果将错误传递给 next（），并且您不会在自定义错误处理程序中进行处理，它将由内置错误处理程序进行处理；错误将与堆栈跟踪一起写入客户端。堆栈跟踪不包含在生产环境中。

If you pass an error to next() and you do not handle it in a custom error handler, it will be handled by the built-in error handler; the error will be written to the client with the stack trace. The stack trace is not included in the production environment.

文档不会对那进行过多介绍有关默认处理程序的更多详细信息，但在查看源代码之后，默认处理程序是名为 finalhandler 。

The docs don't go into that much more detail on the default handler, but after looking at the source code, the default handler is a separate module called finalhandler.

无论如何，要覆盖此处理程序，请参阅Express文档中标题为 编写错误处理程序 。

Anyways, to override this handler, refer to the section in the Express docs titled Writing error handlers.

它解释：

以与其他中间件功能相同的方式定义错误处理中间件功能，除了错误处理功能有四个参数，而不是三个：（错误，要求，结果，下一个）。例如：

app.use(function (err, req, res, next) {
  console.error(err.stack)
  res.status(500).send('Something broke!')
})

在其他 app.use（）和路由调用之后，最后定义错误处理中间件

You define error-handling middleware last, after other app.use() and routes calls

因此，在您的情况下，如果您想回答400，则可能会这样写：

So in your case, if you wanted to respond with a 400, you might write something like this:

const app = express();
const cors = require('cors')
var corsOptions = {
    origin: function (origin: any, callback: any) {
        if (!origin || whitelist.indexOf(origin) !== -1) {
            callback(null, true)
        } else {
            callback(new Error('Not allowed by CORS'))
        }
    }
}
app.use(cors(corsOptions));

// This overrides the default error handler, and must be called _last_ on the app
app.use(function customErrorHandler(err, req, res, next) {
   res.status(400).send('Your custom error message here');
});

也可以在其存储库中包含示例服务器，显示了此erorr处理覆盖。

Express also includes a sample server in its repo, showing this erorr handling override.

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