File Upload — gqlgen

Graphql server has an already built-in Upload scalar to upload files using a multipart request.
It implements the following spec https://github.com/jaydenseric/graphql-multipart-request-spec,
that defines an interoperable multipart form field structure for GraphQL requests, used by
various file upload client implementations.

To use it you need to add the Upload scalar in your schema, and it will automatically add the
marshalling behaviour to Go types.

Configuration

There are two specific options that can be configured for uploading files:

  • uploadMaxSize
    This option specifies the maximum number of bytes used to parse a request body as multipart/form-data.
  • uploadMaxMemory
    This option specifies the maximum number of bytes used to parse a request body as
    multipart/form-data in memory, with the remainder stored on disk in temporary files.

Examples

Single file upload

For this use case, the schema could look like this.

"The `UploadFile, // b.txt` scalar type represents a multipart file upload."

scalar

Upload

"The `Query` type, represents all of the entry points into our object graph."

type

Query

{

...

}

"The `Mutation` type, represents all updates we can make to our data."

type

Mutation

{

singleUpload

(

file

:

Upload

!):

Boolean

!

}

cURL can be used the make a query as follows:

curl localhost:4000/graphql \  -F operations='{ "query": "mutation ($file: Upload!) { singleUpload(file: $file) }", "variables": { "file": null } }' \  -F map='{ "0": ["variables.file"] }' \  -F [email protected]

That invokes the following operation:

{

query

:

`

mutation($file: Upload!) {

singleUpload(file: $file)

}

`

,

variables

:

{

file

:

File

// a.txt

}

}

Multiple file upload

For this use case, the schema could look like this.

"The `Upload` scalar type represents a multipart file upload."

scalar

Upload

"The `File` type, represents the response of uploading a file."

type

File

{

id

:

Int

!

name

:

String

!

content

:

String

!

}

"The `UploadFile` type, represents the request for uploading a file with a certain payload."

input

UploadFile

{

id

:

Int

!

file

:

Upload

!

}

"The `Query` type, represents all of the entry points into our object graph."

type

Query

{

...

}

"The `Mutation` type, represents all updates we can make to our data."

type

Mutation

{

multipleUpload

(

req

:

[

UploadFile

!]!):

[

File

!]!

}

cURL can be used the make a query as follows:

curl localhost:4000/query

\

-F

operations

=

'{ "query": "mutation($req: [UploadFile!]!) { multipleUpload(req: $req) { id, name, content } }", "variables": { "req": [ { "id": 1, "file": null }, { "id": 2, "file": null } ] } }'

\

-F

map

=

'{ "0": ["variables.req.0.file"], "1": ["variables.req.1.file"] }'

\

-F

0

=

@b.txt

\

-F

1

=

@c.txt

That invokes the following operation:

{

query

:

`

mutation($req: [UploadFile!]!)

multipleUpload(req: $req) {

id,

name,

content

}

}

`

,

variables

:

{

req

:

[

{

id

:

1

,

File

,

// b.txt

},

{

id

:

2

,

File

,

// c.txt

}

]

}

}

See the _examples/fileupload package for more examples.

Usage with Apollo

apollo-upload-client needs to be installed in order for file uploading to work with Apollo:

import

ApolloClient

from

"apollo-client"

;

import

{

createUploadLink

}

from

"apollo-upload-client"

;

const

client

=

new

ApolloClient

({

cache

:

new

InMemoryCache

(),

link

:

createUploadLink

({

uri

:

"/graphql"

})

});

A File object can then be passed into your mutation as a variable:

{

query

:

`

mutation($file: Upload!) {

singleUpload(file: $file) {

id

}

}

`

,

variables

:

{

file

:

new

File

(...)

}

}

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