PropertyNameStrategy¶

interface PropertyNameStrategy

Allows configuring how the DSL generates MongoDB paths from KProperty1 instances.

Introduction¶

The KtMongo library uses type-safe Field instances to represent paths in MongoDB queries. For example,

class User(
    val profile: Profile,
)

class Profile(
    val name: String,
)

with(FieldDsl(PropertyNameStrategy.Default)) {
    User::profile / Profile::name
}

which results in the path profile.name.

To build this path, the PropertyNameStrategy.Default strategy uses the name of the fields as they are written in Kotlin code.

Customizing¶

If you use a serialization library that allows renaming fields, like Jackson or KotlinX.Serialization, you may find a mismatch between how your documents are generated and how KtMongo queries try to access them.

@Serializable
data class User(
    @SerialName("f")
    val aSuperLongField: String,
)

with(FieldDsl(PropertyNameStrategy.Default)) {
    User::aSuperLongField
}

which results in the path aSuperLongField which is incorrect: it should be f. In this situation, your KtMongo queries will refer to paths that don't exist.

It is not feasible for KtMongo to provide built-in support for all serialization libraries. However, we do support:

The annotations @BsonId and @SerialName used by the KMongo library, with the modules dev.opensavvy.ktmongo:driver-coroutines-kmongo or dev.opensavvy.ktmongo:driver-sync-kmongo.

You can also create your own strategy to support any other serialization library. To do this, implement this interface. All KtMongo entry-points should provide a way to override the default strategy, for example with the official drivers:

val client = MongoClient.create()
val database = client.getDatabase("my-project")
val collection = database.getCollection<User>("users")
    .asKtMongo(
        nameStrategy = yourCustomNameStrategy,
    )

The different operators that build Field instances are in the FieldDsl interface.

Inheritors¶

Types¶

`Default`¶

object Default : PropertyNameStrategy

Default implementation of PropertyNameStrategy, which always uses the property name exactly as it is written in Kotlin code.

Functions¶

pathOf¶

@LowLevelApi



abstract fun pathOf(property: KProperty1<*, *>): Path

Generates the name of a property.

This is used by the DSL to allow configuring how the notation Foo::bar / Bar::baz is converted into a MongoDB path.

For example, an implementation could add support for the KMongo annotation @BsonId to rename the field _id.