Can't find a codec for class with generics

Working with Data Drivers
,
1

I have typed inline value class for typed identification…

@JvmInline
@Serializable
value class Id<T>(
    @Contextual
    val value: ObjectId = ObjectId()
)

I use this class on all my domain models…

@Serializable
data class Test(
    override var _id: Id<Test> = Id(),
    val value: String,
) 

@Serializable
data class Status(
    override var _id: Id<Status> = Id(),
    var test_id: Id<Test>,
    val value: String
)

...

The database seeding goes well everything works as expected, I see documents in the right form… But when I’m trying to read from database it creates this error…

org.bson.codecs.configuration.CodecConfigurationException:
Can't find a codec for CodecCacheKey{clazz=class Id, types=null}.

Does anyone have a clue how to write Codec for typed value classes because I have no idea?

2

Yeeesssss! I have Solved it…

You have to define codec class for your generic class and use star operator on generic type…

class IdCodec : Codec<Id<*>> {
    override fun encode(writer: BsonWriter, value: Id<*>, encoderContext: EncoderContext) {
        return writer.writeObjectId(value.value)
    }

    override fun decode(reader: BsonReader, decoderContext: DecoderContext): Id<*> {
        return Id<Any>(value = reader.readObjectId())
    }

    override fun getEncoderClass(): Class<Id<*>> = Id::class.java
}

Then register this codec on created database instance…

    val idCodecRegistry = CodecRegistries.fromCodecs(IdCodec())
    var codecRegistry = CodecRegistries.fromRegistries(
        MongoClientSettings.getDefaultCodecRegistry(),
        idCodecRegistry
    )
    val db = mongoClient.getDatabase(db_name).withCodecRegistry(codecRegistry)