Using Mongodb Kotlin drivers with default KMongo codec

mongoDbKotlinDriversWithKMongoCodec.kt

/**
 * Q: Why use KMongo's default codec over the official Mongodb Kotlin drivers' default codec or Kotlinx.serialization?
 * A: Having been using KMongo for several years at an enterprise level, having to switch to a new codec or
 *    rework all of our data to be handled via this new codec seemed like more effort than it was worth at the moment.
 *
 * Q: Isn't KMongo deprecated? Why depend on it just for this?
 * A: Yes it is deprecated, however, it is also assumed/expected that many users of KMongo will still be using
 *    KMongo's nicer / more intuitive query building tools / syntax. Until that query building logic is split off into its own project,
 *    we will still be pulling it in anyways. On top of this, I am just hopeful that the default codec that KMongo utilizes will also
 *    still be available to make transitions for others easier even if the base project is no longer available, fingers crossed!
 */

import com.mongodb.ConnectionString
import com.mongodb.MongoClientSettings
import com.mongodb.kotlin.client.MongoClient
import org.litote.kmongo.KMongo
import org.litote.kmongo.service.ClassMappingType
import org.litote.kmongo.util.KMongoUtil

fun `using KMongo's default codec with the official Mongodb Kotlin drivers`() {
  val connectionString = ConnectionString("mongodb://example:example@localhost:27017")

  /**
   * plain kmongo client, uses KMongo's default codec under the hood
   * which includes Jackson serde among other things
   */
  val kmongoClient = KMongo.createClient(connectionString)

  /**
   * plain mongo kotlin driver client. This utilizes a different default codec
   * under the hood (MongoClientSettings.getDefaultCodecRegistry())
   */
  val mongoDriverClient = MongoClient.create(connectionString)

  /**
   * What the default client settings would look like for the above client
   */
  val defaultMongoClientSettings = MongoClientSettings.builder()
    .applyConnectionString(connectionString)
    .build()

  println(defaultMongoClientSettings.codecRegistry)
  /**
   * output:
   * ProvidersCodecRegistry{
   *   codecProviders=[
   *     ValueCodecProvider{},
   *     BsonValueCodecProvider{},
   *     DBRefCodecProvider{},
   *     DBObjectCodecProvider{},
   *     DocumentCodecProvider{},
   *     CollectionCodecProvider{},
   *     IterableCodecProvider{},
   *     MapCodecProvider{},
   *     GeoJsonCodecProvider{},
   *     GridFSFileCodecProvider{},
   *     Jsr310CodecProvider{},
   *     JsonObjectCodecProvider{},
   *     BsonCodecProvider{},
   *     EnumCodecProvider{},
   *     com.mongodb.client.model.mql.ExpressionCodecProvider@60219a32,
   *     com.mongodb.Jep395RecordCodecProvider@63792a7a,
   *     com.mongodb.KotlinCodecProvider@6911005b
   *   ]
   * }
   */

  /**
   * To utilize the codec that KMongo was using by default on top of the
   * new Mongo Kotlin drivers we can pull it from an object that is exposed by KMongo
   */
  val mongoClientSettingsWithKMongoCodec = MongoClientSettings.builder()
    .codecRegistry(ClassMappingType.codecRegistry(KMongoUtil.defaultCodecRegistry))
    .applyConnectionString(connectionString)
    .build()

  println(mongoClientSettingsWithKMongoCodec.codecRegistry)
  /**
   * output:
   * ProvidersCodecRegistry{
   *   codecProviders=[
   *     ProvidersCodecRegistry{
   *       codecProviders=[
   *         ValueCodecProvider{},
   *         BsonValueCodecProvider{},
   *         DBRefCodecProvider{},
   *         DBObjectCodecProvider{},
   *         DocumentCodecProvider{},
   *         IterableCodecProvider{},
   *         MapCodecProvider{},
   *         GeoJsonCodecProvider{},
   *         GridFSFileCodecProvider{},
   *         Jsr310CodecProvider{},
   *         JsonObjectCodecProvider{},
   *         BsonCodecProvider{}
   *       ]
   *     },
   *     org.litote.kmongo.service.CustomCodecProvider@12223f2b,
   *     ProvidersCodecRegistry{
   *       codecProviders=[
   *         org.litote.kmongo.jackson.JacksonCodecProvider@1e42841a
   *         ]
   *       }
   *     ]
   *   }
   */

  /**
   * Should now be using the KMongo default codec, while still utilizing the official Kotlin drivers
   * for connection. Should behave the exact same as KMongo in terms of serde
   */
  val mongoDriverClientWithKMongoCodec = MongoClient.create(mongoClientSettingsWithKMongoCodec)
}