Uploading files

Apollo Kotlin supports file uploads via the GraphQL multipart request specification.

First, add the following custom scalar mapping to the Apollo Gradle plugin configuration:

build.gradle[.kts]

1
apollo 
{
2
  
service
(
"service"
)
 
{
3
    
mapScalarToUpload
(
"Upload"
)
4
  
}
5
}

In this example, the GraphQL schema defines a custom scalar type named Upload. You can use a different name as needed for your schema.

Note: You don’t need to register a type adapter for Upload, because the mapScalarToUpload method registers it automatically.

Now let’s consider a mutation that takes an Upload as a parameter:

1
mutation
 
SingleUpload
(
$file
:
 
Upload
!
)
 
{
2
  
singleUpload
(
file
:
 
$file
)
 
{
3
    
id
4
    
path
5
    
filename
6
    
mimetype
7
  
}
8
}

Create an instance of Upload using one of the factory methods:

1
2
val
 upload 
=
 File
.
toUpload
(
"application/json"
)
3

4
5
val
 upload 
=
 DefaultUpload
.
Builder
(
)
6
              
.
fileName
(
"filename.txt"
)
7
              
.
content
 
{
 sink 
->
8
                okioSource
.
use
 
{
 sink
.
writeAll
(
it
)
 
}
9
              
}
10
              
.
build
(
)

And execute your mutation:

1
val
 response 
=
 apolloClient
.
mutation
(
SingleUploadMutation
(
file 
=
 upload
)
)
.
execute
(
)