Liflig Document Store

Kotlin library implementing the repository pattern for storing documents as JSONB in Postgres.

Provides:

• Extendible repository class, with default implementations of CRUD operations
• Optimistic locking
• Transaction management
• Migration utilities

Document Store uses the JDBI library for convenient database access.

This library is currently only distributed in Liflig internal repositories.

Contents:

• Usage
  • Implementing SerializationAdapter
• Contributing

Usage

Liflig Document Store works on the assumption that all database tables look alike, using the jsonb column type from Postgres to store data. So you first have to create your table like this:

CREATE TABLE example
(
  -- Can have type `text` if using `StringEntityId`, or `bigint` if using `IntegerEntityId`
  id          uuid        NOT NULL PRIMARY KEY,
  created_at  timestamptz NOT NULL,
  modified_at timestamptz NOT NULL,
  version     bigint      NOT NULL,
  data        jsonb       NOT NULL
)

Then, define an entity in your application. If you use kotlinx-serialization, the entity must be @Serializable.

import kotlinx.serialization.Serializable
import no.liflig.documentstore.entity.Entity
import no.liflig.documentstore.entity.UuidEntityId

@Serializable
data class ExampleEntity(
  override val id: ExampleId,
  val name: String,
) : Entity<ExampleId>

@Serializable
@JvmInline
value class ExampleId(override val value: UUID) : UuidEntityId {
  override fun toString() = value.toString()
}

Next, implement a Repository for your entity. See below for the implementation of KotlinSerialization.

import no.liflig.documentstore.entity.Versioned
import no.liflig.documentstore.repository.RepositoryJdbi
import org.jdbi.v3.core.Jdbi

class ExampleRepository(jdbi: Jdbi) :
  RepositoryJdbi<ExampleId, ExampleEntity>(
    jdbi,
    tableName = "example",
    serializationAdapter = KotlinSerialization(ExampleEntity.serializer()),
  ) {

  fun getByName(name: String): Versioned<ExampleEntity>? {
    // To implement filtering on the entity's fields, we use the getByPredicate method inherited
    // from RepositoryJdbi. It lets us provide our own WHERE clause, and a lambda to bind arguments.
    // In the WHERE string, we use JSON operators from Postgres (->>) to query the entity's fields.
    return getByPredicate("data->>'name' = :name") {
      // Binds to the :name parameter in the query
      bind("name", name)
    }
      .firstOrNull()
  }
}

This inherits CRUD methods (create, get, update and delete) from RepositoryJdbi, so we can use it like this:

val exampleRepo: ExampleRepository

val (entity, version) = exampleRepo.create(
  ExampleEntity(
    id = ExampleId(UUID.randomUUID()),
    name = "test",
  )
)

println("Created entity with name '${entity.name}'")

Finally, when setting up our Jdbi instance to connect to our database, we have to install the DocumentStorePlugin (this registers argument types that RepositoryJdbi depends on):

import javax.sql.DataSource
import org.jdbi.v3.core.Jdbi
import org.jdbi.v3.core.kotlin.KotlinPlugin
import org.jdbi.v3.postgres.PostgresPlugin

fun createJdbiInstance(dataSource: DataSource): Jdbi {
  return Jdbi.create(dataSource)
    .installPlugin(KotlinPlugin())
    .installPlugin(DocumentStorePlugin())
}

Implementing SerializationAdapter

The KotlinSerialization class used in the ExampleRepository above is an implementation of the SerializationAdapter interface from Liflig Document Store. This interface allows you to choose your own JSON serialization library when using Document Store. Here is an example implementation for kotlinx-serialization:

import kotlinx.serialization.KSerializer
import kotlinx.serialization.json.Json
import no.liflig.documentstore.entity.Entity
import no.liflig.documentstore.repository.SerializationAdapter

private val json = Json {
  encodeDefaults = true
  ignoreUnknownKeys = true
}

class KotlinSerialization<EntityT : Entity<*>>(
  private val serializer: KSerializer<EntityT>,
) : SerializationAdapter<EntityT> {
  override fun toJson(entity: EntityT): String = json.encodeToString(serializer, entity)

  override fun fromJson(value: String): EntityT = json.decodeFromString(serializer, value)
}

Contributing

To check build before pushing:

mvn verify

GitHub Actions will automatically release a new version for commits on master.