How to serialize dynamic keys of a json with kotlinx

Question

I have a json with this kind of key:

...
    "metaData": {
        "date:create": "2019-11-13t15:42:02+01:00",
        "date:modify": "2019-11-13t15:42:02+01:00",
        "exif:ColorSpace": "1",
        "exif:ExifImageLength": "1500",
        "exif:ExifImageWidth": "1125",
        "exif:ExifOffset": "38",
        "exif:Orientation": "1",
        "jpeg:colorspace": "2",
        "jpeg:sampling-factor": "1x1,1x1,1x1"
    },
...

All the keys in the metaData object are dynamic (not really but there's hundred of different keys) how can i serialize this object without having to create a class with all the possible keys.

This is my work:

@Serializable
data class Image(
    val name: String? = null,
    val uid: String,
    val createdAt: String? = null,
    val updatedAt: String? = null,
    val metaData: MetaData? = null,
)

@Serializable
data class MetaData (
    @SerialName("date:create")
    val dateCreate: String,

    @SerialName("date:modify")
    val dateModify: String,

    @SerialName("exif:ColorSpace")
    val exifColorSpace: String,

    @SerialName("exif:ExifImageLength")
    val exifExifImageLength: String,

    @SerialName("exif:ExifImageWidth")
    val exifExifImageWidth: String,

    @SerialName("exif:ExifOffset")
    val exifExifOffset: String,

    @SerialName("exif:Orientation")
    val exifOrientation: String,

    @SerialName("jpeg:colorspace")
    val jpegColorspace: String,

    @SerialName("jpeg:sampling-factor")
    val jpegSamplingFactor: String
)

score 3 · Accepted Answer · answered Nov 13 '19 at 16:12

You can use a JSONObject to serialize dynamically the metadata. Your Metadata class is useless with this solution, your Image instance will have a JSONObject as metadata property :

data class Image(
    val name: String? = null,
    val uid: String,
    val createdAt: String? = null,
    val updatedAt: String? = null,
    val metaData: JSONObject? = null,
)

How to serialize dynamic keys of a json with kotlinx

1 Answers1