hey guys, I meet a problem when insert a data clas...

# ktor

[kurt_steiner]

hey guys, I meet a problem when insert a data class into the mongodb collection, this is my model

data class User(
    @BsonId
    val id: ObjectId,
    val name: String,
    val age: Int
) {
    override fun toString(): String {
        return "User(id=${id}, name=${name}, age=${age})"
    }
}

and this is revalent code

class UserService(val database: MongoDatabase) {
    val users = database.getCollection("users", User::class.java)

    fun insertOne(name: String, age: Int): User {
        val user = User(
            id = ObjectId(),
            name = name,
            age = age
        )

        users.insertOne(user)
        return user
    }
}

and the error is

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

so can you tell me how to insert a custom class into collection ?

[Marcus Ilgner]

this seems to be a MongoDB-specific issue. Have you looked at https://www.mongodb.com/docs/drivers/kotlin/coroutine/current/fundamentals/data-formats/codecs/ yet?

[kurt_steiner]

ok. let's me check it

[kurt_steiner]

by the way, can kotlinx.serialization solve it ?

[Marcus Ilgner]

that should be a straightforward implementation for the Codec. There might even be an existing one in https://github.com/ltj/bson4k

[kurt_steiner]

and the example of writing codec is too simple, it is just about boolean type but not class, can you give me an example ?

[Marcus Ilgner]

They also have a custom MonolightCodec in the examples which encodes a class. Personally I've never used any of these libraries so I can't say more than that 😉

[kurt_steiner]

indeed, i have never used bson before, I think it is about key-value type, right?
if I am right, how to write a key, and how to write the value ?
that is the main problem 😋

[Marcus Ilgner]

I'm not sure that it necessarily cares about key-value types only. It's just a binary-optimized version of a format like JSON. But in JSON one can encode other values, too. I.e. true , 1.23 or "foobar" are all valid JSON values, even if they don't make up a full JSON object.

[kurt_steiner]

thanks for you patience, I have found the answer, for key, just write writeName is ok

[Marcus Ilgner]

since bson4k can encode any object that supports Kotlin Serialization, I'd probably start looking there to serialize a data class

[kurt_steiner]

wtf, still error ?

[Marcus Ilgner]

that's unexpected - the new codec registry seems to be missing the default Java standard library encoders? 😖 I'm pretty certain that these should be available from the start...

[Marcus Ilgner]

you might want to try sth like this

val newRegistry = CodecRegistries.fromRegistries(
    CodecRegistries.fromCodecs(MyEnumCodec()),
    MongoClientSettings.getDefaultCodecRegistry()
)

[kurt_steiner]

eh, still the same, but i found that there is no problem with insert, but findMany

fun findMany(name: String? = null, age: Int? = null): List<User> {
        val queryParams = mutableListOf<Bson>()

        if (name != null) {
            queryParams.add(Filters.eq(User::name.name, name))
        }

        if (age != null) {
            queryParams.add(Filters.eq(User::age.name, age))
        }

        return users.find(Filters.and(queryParams)).toList()
    }

[kurt_steiner]

and the error is the same

[Marcus Ilgner]

you might have more luck in some MongoDB-specific community...

[kurt_steiner]

thanks

[kurt_steiner]

oh, I find the solution, i forget to add this default registry MongoClientSettings.getDefaultCodecRegistry()

[kurt_steiner]

but that follow another problem, I have follow the tutorial, but nothing

[kurt_steiner]

ok, I fix it, finally