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bodyParser.json() doesn't support custom type option #247

hh54188 opened this Issue Jun 7, 2017 · 2 comments


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hh54188 commented Jun 7, 2017

Here is my script post request handler part:

const bodyParser = require('body-parser')

app.use( bodyParser.json({ type: 'secret' }) );       // to support JSON-encoded bodies
app.use( bodyParser.urlencoded({     // to support URL-encoded bodies
    extended: true
}) );'/upload', function (req, res) {

The post request from client set a custom Content-Type which is secret. Then I want the server resolve the post data as json. So I set type parameter to secret.

However, in the post handler function, I can print the Content-Type value in header is secret, but the req.body result is empty. It seems the bodyParser doesn't resolve the request.

If I change the request Content-Type to default application/json and without setting the type parameter, everything would be all right.

Is there anything wrong with my code ?


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dougwilson commented Jun 7, 2017

Hi @hh54188 for the type option:

This option can be a function or a string. If a string, type option is passed directly to the type-is library and this can be an extension name (like json), a mime type (like application/json), or a mime type with a wildcard (like / or */json). If a function, the type option is called as fn(req) and the request is parsed if it returns a truthy value.

So since you are providing a string that does not have a / (all valid content-type values require a slash -- see the HTTP specification), then since there is no normal reason this would represent the content-type value, instead it is defined to be the file extension, i.e. it is looking for a body that would result in a .secret file name.

If you want to match against an invalid content-type value, that is fine, but you just need to use the function form of the type option:

app.use( bodyParser.json({ type: (req) => req.get('Content-Type') === 'secret' }) ); // to support JSON-encoded bodies

@dougwilson dougwilson closed this Jun 7, 2017

@dougwilson dougwilson self-assigned this Jun 7, 2017

@dougwilson dougwilson added the question label Jun 7, 2017


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hh54188 commented Jun 7, 2017

Thank you for your reply.

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