File Configuration

FileConfig customizes how KraftAdmin validates and accepts uploaded files.

It is used together with @KraftAdminField when the field uses one of the media input types such as:

FormInputType.FILE
FormInputType.IMAGE
FormInputType.VIDEO
FormInputType.AUDIO
FormInputType.DOCUMENT

@KraftAdminField(
    inputType = FormInputType.FILE,
    fileConfig = FileConfig(...)
)

ℹ️ Info

If no FileConfig is provided, KraftAdmin uses sensible defaults.

Default Configuration

@KraftAdminField(
    inputType = FormInputType.FILE,
    fileConfig = FileConfig()
)

Default values:

Property	Default
`multiple`	`false`
`maxFiles`	`1`
`allowedExtensions`	Any
`allowedMimeTypes`	Any
`minSizeBytes`	`0`
`maxSizeBytes`	`10 MB`

Multiple Uploads

Allow uploading more than one file.

@KraftAdminField(
    inputType = FormInputType.FILE,
    fileConfig = FileConfig(
        multiple = true,
        maxFiles = 5
    )
)
var documents: List<String> = emptyList()

Maximum Files

Limit how many files may be uploaded.

fileConfig = FileConfig(
    multiple = true,
    maxFiles = 10
)

Allowed Extensions

Restrict uploads by file extension.

fileConfig = FileConfig(
    allowedExtensions = [
        FileExtension.JPG,
        FileExtension.PNG,
        FileExtension.WEBP
    ]
)

Supported extensions include:

Images

JPG
JPEG
PNG
GIF
WEBP
SVG

Documents

PDF
DOC
DOCX
TXT
CSV
XLS
XLSX
PPT
PPTX

Video

MP4
WEBM
MOV

Audio

MP3
WAV
OGG
AAC
FLAC

Allowed MIME Types

Validate uploaded files using MIME types.

fileConfig = FileConfig(
    allowedMimeTypes = [
        MimeType.IMAGE_JPEG,
        MimeType.IMAGE_PNG
    ]
)

This provides stronger validation than relying on file extensions alone.

Minimum File Size

Reject files smaller than a specified size.

fileConfig = FileConfig(
    minSizeBytes = 1024
)

Only files larger than 1 KB are accepted.

Maximum File Size

Restrict the maximum upload size.

fileConfig = FileConfig(
    maxSizeBytes = 20 * 1024 * 1024
)

The above example allows uploads up to 20 MB.

Image Upload Example

@KraftAdminField(
    label = "Profile Photo",
    inputType = FormInputType.IMAGE,
    fileConfig = FileConfig(
        allowedExtensions = [
            FileExtension.JPG,
            FileExtension.PNG,
            FileExtension.WEBP
        ],
        maxSizeBytes = 5 * 1024 * 1024
    )
)
var avatar: String? = null

PDF Upload Example

@KraftAdminField(
    label = "Resume",
    inputType = FormInputType.FILE,
    fileConfig = FileConfig(
        allowedExtensions = [
            FileExtension.PDF
        ],
        allowedMimeTypes = [
            MimeType.PDF
        ]
    )
)
var resume: String? = null

Multiple Document Upload

@KraftAdminField(
    label = "Attachments",
    inputType = FormInputType.FILE,
    fileConfig = FileConfig(
        multiple = true,
        maxFiles = 10,
        maxSizeBytes = 50 * 1024 * 1024
    )
)
var attachments: List<String> = emptyList()

Best Practices

💡 Tip

Always validate both file extensions and MIME types. Extensions are easy to rename, while MIME types provide an additional layer of verification.