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Octavius Database

An explicit, SQL-first data access layer for Kotlin & PostgreSQL

KDoc API KDoc Core Maven Central Status

It's not an ORM. It's a ROME (Relational-Object Mapping Engine). Because all queries lead to ROME.

Warning

This project is legacy and is no longer actively developed. It has been superseded by octavius-postgresql — a PostgreSQL driver that speaks Wire Protocol v3.2 directly, a client (data access layer) built on top of it, and a migrator, published as separate artifacts.

Much of what lives here exists to work around pgjdbc — text-protocol composites, enums the library had to be taught about, a stateful ResultSet, no named parameters — and the new driver answers all of that natively. What was left over is the client, deliberately a much smaller thing than a port would have been.

Nothing is being taken away: the released artifacts stay on Maven Central and the code below still works. But new work happens in octavius-postgresql, and new projects should start there.

Where Everything Went

Nothing here was dropped for want of a home. Most of it was a workaround for pgjdbc and the new driver answers it natively; the rest moved, and a few things changed shape enough to be worth a sentence.

Here There
SelectQueryBuilder and the other three — with(), recursive(), fromSubquery, page, forUpdate, onConflict, fromSelect, using, returning The four builders, method for method
QueryFragment, withParam, join QueryFragment
dynamic_dto dynamic_dto — same idea, a real composite instead of a text-protocol one
dynamic_map plain ROW(...) — see below
.options { } per-query converters — see below
TypeHandler<T>, GlobalTypeHandler<T> ResultConverter + ParameterConverter — see below
@MapKey @PgName, and it applies in both directions
@PgEnum, @PgComposite, @DynamicallyMappable @PgEnumType, @PgCompositeType, @DynamicallyMappable, scanned by client-scanner
toDataObject(), toDataMap() the same two
DataMapper, .toListOf { map -> … } a ResultConverter<Row, T> — see below
TransactionPlan, TransactionStep, StepHandle Transaction Plans, and every failure names its step on the exception's path
PgChannelListener LISTEN / NOTIFY
CALL with IN/OUT/INOUT Functions and Procedures
bulk unnest Bulk Writes
DataResult, quoteAsPgIdentifier, PgTyped/withPgType, QualifiedName, CaseConvention the same names
flyway-integration migrations, which is its own migrator rather than an adapter
spring-integration driver-spring-integration
api and core, split by platform pg-model for what is multiplatform, driver and client for the rest

dynamic_map was a workaround, and the workaround is gone

An anonymous record did come back — over the text protocol, which is the whole of the problem. What arrived was strings, the per-field OIDs having been dropped on the way, and a map with no target class has nothing else to infer a type from. So dynamic_map carried the OID as data:

CREATE TYPE public.dynamic_map_entry AS (type_oid oid, key text, raw_value text);

One entry per key, each stating its own type, which is what let a TypeHandler decode a timestamptz or a custom enum instead of handing back the text. And it is exactly why the type could never be stored: those OIDs sit in the rows, and a user-defined type's OID is not the same one after a dump and restore.

Registering types on the connection was the other road, and technically open — but it would have had to be wired into every physical connection a pool hands out, which with HikariCP in front is not something to look forward to maintaining.

The new driver speaks the binary protocol, so a record's fields arrive with their OIDs in the row description and there is nothing left to work around. A ROW(...) in the SELECT clause is read as a map with its types intact — no type to install, no ~> operator, and no warning to attach, an anonymous record having nowhere to rot:

session.createNativeQuery(
    """
    SELECT ROW(
        'id', c.id,
        'tributes', ARRAY(SELECT ROW('amount', t.amount) FROM tributes t WHERE t.citizen_id = c.id)
    ) AS r
    FROM citizens c WHERE c.id = 1
    """
).fetchFieldStrict<Map<String, Any?>>()

// {id=1, tributes=[{amount=40}, {amount=15}]}

The 1:N aggregation dynamic_map was built for works the same way, and so does the part that mattered: a date comes back a LocalDate, a uuid a Uuid, a timestamptz an Instant. See the raw forms.

QueryOptions became one mechanism instead of five fields

.options { } carried five different things. Four of them are one thing now — a converter registered on a query, ahead of the session's and discarded with it:

QueryOptions field Now
typeHandlers registerResultConverter / registerParameterConverter on the query
json dynamicTypes.resultConverter(json), registered the same way
customCompositeMappers a converter narrowed on sourceType.name
returnCompositeAsMap(name) compositesAsMaps(name)
returnAllCompositesAsMaps() compositesAsMaps()

The last two are one function with an overload that takes several names at once. One difference worth knowing: it claims a value only where the caller asked for Any or Map, so naming a class in the same query still answers with the class, and a data class is untouched below its own surface. Here the option won over everything, including a declared property type.

DataMapper became a converter keyed on Row

toListOf(params, mapper) handed the library a function and got a List<T> back. The same shape is a ResultConverter whose source class is Row: fetchObjects<T>() hands the whole row to the converters, so one that claims Row is called once per row and is exactly where the mapper stood.

object CitizenFromRow : ResultConverter<Row, Citizen> {
    override val supportedSourceClass = Row::class

    override fun canConvert(sourceClass: KClass<*>, expectedType: KType, sourceType: PgType, context: DeserializationContext) =
        expectedType.classifier == Citizen::class

    override fun convert(source: Row, expectedType: KType, sourceType: PgType, context: DeserializationContext) =
        Citizen(source.get("name"), source.get("province"))
}

session.createNativeQuery("SELECT name, province FROM citizens")
    .registerResultConverter(CitizenFromRow)
    .fetchObjects<Citizen>()

Two things it gains on the way. forEachObject runs through the same converter, so the mapping streams rather than only filling a list. And the registration can go on the session's typeManager instead of on the query — then fetchObjects<Citizen>() maps that way everywhere, which is not something a per-call mapper could say.

The reflective mapping is still there for the ordinary case: a data class whose properties match the columns needs no converter at all, which is what most DataMappers were written to do by hand.

TypeHandler split in two, and is not scanned

One interface doing both directions became two — ResultConverter and ParameterConverter — each deciding for itself what it claims through canConvert, which is what lets one narrow on the PostgreSQL type as well as on the Kotlin one. Register on the session's typeManager for the old GlobalTypeHandler, or on a single query for the old per-query one.

The one thing that does not carry over: client-scanner does not pick them up off the classpath. A TypeHandler here was resolved from a map keyed by OID and class — one per type, no overlap, no order to get wrong — which made scanning them safe. There, converters are consulted newest-first and a later one wins, so registration order is the only override mechanism there is, and a classpath scan has no defined order. They are registered by hand, in one place, on purpose: What It Does Not Scan.

What is gone rather than moved

  • ? escaping for JSONB operators. Parameters are @name and reach the wire as $1, so a ? in the SQL is never anything but a ?.
  • disableCoreTypeInitialization. Nothing is created behind your back to begin with — dynamic_dto goes in a migration, or in an explicit install().
  • showBanner. There is no startup the library owns: you hand it a DataSource, install() is a call you make, and the migrator is a library rather than a command. Nowhere left to print one. 🫡

The one thing that came with it unchanged

It's not an ORM. It's a ROME. Written here, and far too good to leave behind.

Philosophy (The Pax Romana of Data)

Just as Augustus brought order to a republic torn apart by the chaos of unchecked power, Octavius brings order to the chaotic republic of database interactions. The Senate of abstraction is dissolved. SQL rules supreme.

Octavius was built to bring order to the chaotic republic of database interactions. It rejects the unpredictable "magic" of traditional ORMs and returns the power to the rightful ruler: SQL.

Principle Description
Query is Imperator Your SQL query dictates the shape of data — not the framework.
Object is a Vessel A data class is simply a type-safe container for query results.
Explicitness over Magic No lazy-loading, no session management, no dirty checking.

Features

  • Fluent Query Builders — SELECT, INSERT, UPDATE, DELETE with named parameters, subqueries, and CTE support
  • Automatic Type Mapping — PostgreSQL COMPOSITE, ENUM, ARRAY and Custom Type Handlers (Global & Per-Query) ↔ Kotlin types
  • Dynamic Type System — Polymorphic storage & ad-hoc object mapping with dynamic_dto and dynamic_map
  • Transaction Plans — Multi-step atomic operations with step dependencies
  • Dynamic Filters — Safe, composable WHERE clauses with QueryFragment
  • Stored Procedures — CALL with automatic IN/OUT/INOUT handling, composite & array expansion
  • LISTEN / NOTIFY — Flow-based async notifications on a dedicated connection outside the pool

Every design choice in Octavius is intentional. The reasoning behind them is laid out in the Design Philosophy.

Quick Start

// Define your data class — it maps directly to query results
data class Legionnaire(val id: Int, val name: String, val rank: String)

// Query with named parameters
val legionnaires = dataAccess.select("id", "name", "rank")
    .from("legions")
    .where("enlisted_year > @year")
    .orderBy("name")
    .toListOf<Legionnaire>("year" to 24)

Query Builders

// SELECT with pagination
val senators = dataAccess.select("id", "name", "province")
    .from("senate")
    .where("active = true")
    .orderBy("appointed_at DESC")
    .limit(10)
    .offset(20)
    .toListOf<Senator>()

// INSERT with RETURNING
val newId = dataAccess.insertInto("citizens")
    .value("name")
    .value("tribe")
    .returning("id")
    .toField<Int>(mapOf("name" to "Marcus Aurelius", "tribe" to "Cornelia"))

// UPDATE with expressions
dataAccess.update("legion_supplies")
    .setExpression("quantity", "quantity - 1")
    .where("id = @id")
    .execute("id" to supplyId)

// DELETE
dataAccess.deleteFrom("expired_mandates")
    .where("expires_at < NOW()")
    .execute()

Type Mapping

Automatic conversion between PostgreSQL and Kotlin types.

Standard Types

PostgreSQL Kotlin Notes
int2, smallserial Short
int4, serial Int
int8, bigserial Long
float4 Float
float8 Double
numeric BigDecimal
text, varchar, char String
bool Boolean
uuid Uuid kotlin.uuid.Uuid
bytea ByteArray
json, jsonb JsonElement kotlinx.serialization.json
void Unit Return type of void functions (e.g. pg_notify)
date LocalDate kotlinx.datetime *
time LocalTime kotlinx.datetime
timestamp LocalDateTime kotlinx.datetime *
timestamptz Instant kotlin.time *
interval Duration kotlin.time *

* Supports PostgreSQL infinity values (infinity, -infinity). See Type System for details.

Arrays of all standard types are supported and map to List<T>.

Custom Types

// PostgreSQL COMPOSITE TYPE → Kotlin data class
@PgComposite
data class Province(val name: String, val capital: String, val governor: String)

// PostgreSQL ENUM → Kotlin enum
@PgEnum(schema = "cursus_honorum")
enum class Magistrature { Quaestor, Aedile, Praetor, Consul, Censor }

// Works seamlessly in queries
data class Senator(val id: Int, val rank: Magistrature, val homeProvince: Province)

val senators = dataAccess.select("id", "rank", "home_province")
    .from("senate")
    .toListOf<Senator>()  // Types converted automatically

Custom Type Handlers

Extend the type system for any PostgreSQL type (e.g., circle, ltree) by implementing GlobalTypeHandler<T>. Handlers are automatically discovered via classpath scanning.

object PgCircleHandler : GlobalTypeHandler<PgCircle> {
    override val pgTypeName = "circle"
    override val kotlinClass = PgCircle::class
    override val fromPgString = { s: String -> /* parse <(x,y),r> */ }
    override val toPgString = { c: PgCircle -> "<(${c.x},${c.y}),${c.radius}>" }
}

Per-Query Overrides

Need to change a mapping, bypass reflection, or return a composite as a Map for just one specific query? Use the .options() block without affecting global state:

val results = dataAccess.select("*").from("classified_reports")
    .options { 
        registerTypeHandler(LegacyDateHandler) 
        returnCompositeAsMap("metadata")
    }
    .toListOf<Report>()

See Type System: Per-Query Configuration for full details.

Dynamic Type System (dynamic_dto & dynamic_map)

Octavius provides a powerful bridge between PostgreSQL and Kotlin's type system using the dynamic_dto (JSONB-based storage) and dynamic_map (ad-hoc projections) composite types. They allow you to map complex, nested, or polymorphic data on the fly without creating strict database schema types for every nested object. These types are automatically initialized in the public schema on startup.

1. Ad-hoc Object Mapping

Construct Kotlin objects directly in SQL using jsonb_build_object — no need to define PostgreSQL COMPOSITE types. Perfect for JOINs and projections where you want nested results without schema changes.

@DynamicallyMappable(typeName = "citizen_profile")
@Serializable
data class CitizenProfile(val tribe: String, val rights: List<String>)

data class CitizenWithProfile(val id: Int, val name: String, val profile: CitizenProfile)

// The database packages the nested object, Octavius unpacks it. Zero boilerplate.
val citizens = dataAccess.rawQuery("""
    SELECT
        c.id,
        c.name,
        dynamic_dto(
            'citizen_profile',
            jsonb_build_object('tribe', p.tribe, 'rights', p.rights)
        ) AS profile
    FROM citizens c
    JOIN citizen_profiles p ON p.citizen_id = c.id
""").toListOf<CitizenWithProfile>()

Why use this? Usually, to get a citizen with their profile in one query, you'd fetch flat columns (citizen_id, citizen_name, profile_tribe...) and manually map them, create a database VIEW or COMPOSITE. With ad-hoc mapping, you construct the nested structure directly in SQL. The database does the packaging, Octavius does the unpacking — zero boilerplate.

2. Polymorphic Queries (Row-level)

Store different entity types in a single table and query them safely as a list of Kotlin interfaces.

// 1. Define a sealed interface
sealed interface MonumentRecord

@DynamicallyMappable(typeName = "inscription")
@Serializable
data class Inscription(val text: String, val lang: String) : MonumentRecord

@DynamicallyMappable(typeName = "relief")
@Serializable
data class Relief(val subject: String) : MonumentRecord

// Database: CREATE TABLE monument_records (id INT, record dynamic_dto);

// 2. Fetch directly to a list of your interface
val records = dataAccess.select("record")
    .from("monument_records")
    .toColumn<MonumentRecord>()

// Returns: [Inscription(...), Relief(...), Inscription(...)]

Functions and Procedures

Octavius stays true to its SQL-first philosophy. Invoke functions and procedures directly using native PostgreSQL syntax:

// Functions (SELECT * FROM func)
val result = dataAccess.select("*").from("calculate_tribute(@province, @year)")
    .toField<Int>("province" to "Britannia", "year" to 43)

// Procedures (CALL proc)
val result = dataAccess.rawQuery("CALL register_conscript(@legion_id, @new_rank)")
    .toSingleStrict(
        "legion_id" to 7,
        "new_rank" to null.withPgType("text")
    )

Safe Dynamic Filters

Build complex WHERE clauses without SQL injection risks:

fun buildFilters(name: String?, minRank: Int?, province: Province?) = listOfNotNull(
    name?.let { "name ILIKE @name" withParam ("name" to "%$it%") },
    minRank?.let { "rank_order >= @minRank" withParam ("minRank" to it) },
    province?.let { "home_province = @province" withParam ("province" to it) }
).join(" AND ")

val filter = buildFilters(name = "Julius", minRank = 3, province = null)
val senators = dataAccess.select("*")
    .from("senate")
    .where(filter.sql)
    .toListOf<Senator>(filter.params)

Transactions

Octavius supports two powerful interaction patterns for atomic operations.

1. Transaction Blocks (Imperative)

The simplest way to execute multiple operations. Transactions follow a fail-fast policy: they are automatically rolled back if the block returns DataResult.Failure or throws an exception.

val result = dataAccess.transaction {
    val citizenId = insertInto("citizens")
        .value("name")
        .returning("id")
        .toField<Int>("name" to "Marcus Aurelius")
        .getOrElse { return@transaction it }

    insertInto("citizen_profiles")
        .values(listOf("citizen_id", "bio"))
        .execute("citizen_id" to citizenId, "bio" to "Stoic philosopher")
        .getOrElse { return@transaction it }

    DataResult.Success(citizenId)
}

2. Transaction Plans (Declarative)

Execute multi-step operations with complex dependencies between steps. Results from previous steps can be referenced in subsequent steps without nested callbacks or manual state management.

val plan = TransactionPlan()

// Step 1: Record the edict, get handle to future ID
val edictIdHandle = plan.add(
    dataAccess.insertInto("edicts")
        .values(listOf("issuer_id", "total_tribute"))
        .returning("id")
        .asStep()
        .toField<Int>(mapOf("issuer_id" to consulId, "total_tribute" to tribute))
)

// Step 2: Assign levy items using the handle
for (item in levyItems) {
    val levyItem: Map<String, Any?> = mapOf(
        "edict_id" to edictIdHandle.field(),  // Reference future value
        "province_id" to item.provinceId,
        "amount" to item.amount
    )

    plan.add(
        dataAccess.insertInto("edict_items")
            .values(levyItem)
            .asStep()
            .execute(levyItem)
    )
}

// Execute all steps in single transaction
dataAccess.executeTransactionPlan(plan)

LISTEN / NOTIFY

Subscribe to PostgreSQL channels and receive real-time notifications as a Kotlin Flow:

// Send a notification
dataAccess.notify("legion_dispatch", "legion_id:VII")

// Listen on a dedicated connection (outside the HikariCP pool)
dataAccess.createChannelListener().use { listener ->
    listener.listen("legion_dispatch", "senate_decrees")

    listener.notifications()
        .collect { notification ->
            when (notification.channel) {
                "legion_dispatch" -> handleDispatch(notification.payload)
                "senate_decrees"  -> handleDecree(notification.payload)
            }
        }
}

Each PgChannelListener holds its own dedicated JDBC connection, separate from the query pool. Notifications sent inside a transaction are only delivered after commit.

Error Handling

Octavius distinguishes between Database Execution Errors (returned safely) and Fatal Developer Errors (thrown).

  • Queries Never Throw (On Runtime Errors): If a query is syntactically correct and reaches the database, it returns a DataResult.Failure(error) instead of throwing. This forces explicit handling of expected database errors like constraint violations, lock timeouts, or missing records.
  • Fail-Fast for Bugs: If an obvious developer mistake is made (e.g., invalid SQL syntax, a missing WHERE clause in a DELETE, or a Kotlin type mapping mismatch), Octavius throws a standard exception (FatalDatabaseException). It fails fast because these errors represent broken code that should be caught and fixed during development.
  • Rich Context: Every exception includes a QueryContext that provides a clean visualization of the high-level SQL, the low-level JDBC query, and the exact parameters involved (great for logging!).
val result = dataAccess.insertInto("citizens")
    .value("name")
    .returning("id")
    .toField<Int>("name" to "Marcus Aurelius")

result
    .onSuccess { id -> println("New citizen ID: $id") }
    .onFailure { error ->
        when (error) {
            is ConstraintViolationException -> println("Conflict in: ${error.constraintName}")
            is DataOperationException -> println("Operation failed: ${error.messageEnum}")
            is TransactionException -> println("Transient error: ${error.errorType}")
            else -> println("Database error: $error")
        }
    }

See Error Handling for the full exception hierarchy and debugging tips.

Configuration

Using Properties File

Create a database.properties file in src/main/resources:

db.url=jdbc:postgresql://localhost:5432/roma
db.username=augustus
db.password=spqr
db.schemas=public,cursus_honorum
db.packagesToScan=com.roma.domain,com.roma.dto

# Custom HikariCP settings
db.hikari.maximumPoolSize=20
db.hikari.minimumIdle=5

# Optional settings
db.setSearchPath=true
db.dynamicDtoStrategy=AUTOMATIC_WHEN_UNAMBIGUOUS
db.disableCoreTypeInitialization=false

Load it in your application:

// From properties file
val dataAccess = OctaviusDatabase.fromConfig(
    DatabaseConfig.loadFromFile("database.properties")
)

Direct Configuration

val dataAccess = OctaviusDatabase.fromConfig(
    DatabaseConfig(
        dbUrl = "jdbc:postgresql://localhost:5432/roma",
        dbUsername = "augustus",
        dbPassword = "spqr",
        dbSchemas = listOf("public"),
        packagesToScan = listOf("com.roma.domain"),
        hikariProperties = mapOf("maximumPoolSize" to "20")
    )
)

// From existing DataSource
val dataAccess = OctaviusDatabase.fromDataSource(existingDataSource, ...)

Database Migrations

Octavius provides an optional integration with Flyway for schema migrations via the :flyway-integration module.

val dataAccess = OctaviusDatabase.fromConfig(
    config = config,
    migrationRunner = FlywayMigrationRunner.create(
        schemas = config.dbSchemas,
        baselineVersion = "1"
    )
)

See Flyway Migrations in the configuration guide for details.

Documentation

For detailed guides and examples, see the full documentation:

  • Configuration - Initialization, DatabaseConfig, Flyway (optional), core types, Type Registry scanning, JSON Configuration, DynamicDto strategy
  • Multiplatform Support - Shared DTOs, Multiplatform BigDecimal, and JS serializers
  • Lifecycle & Shutdown - Proper cleanup, .use {} block, common integration patterns
  • Query Builders - SELECT (FOR UPDATE), INSERT (ON CONFLICT), UPDATE, DELETE, fragments, .options() and builder modes
  • Functions & Procedures - CALL, SELECT, IN/OUT, PgTyped resolution
  • Executing Queries - Terminal methods, DataResult matrix, iterative execution
  • Parameter Handling - Named parameters (@), JSONB operator escaping (?), collections & flattening, unnest and bulk operations, identifiers escaping
  • Data Mapping - toDataMap(), toDataObject(), @MapKey, nested structures
  • ORM-Like Patterns - CRUD patterns, real-world examples
  • Transactions - Transaction blocks, TransactionPlan, StepHandle, passing data between steps , propagation, isolation, read-only, timeouts, errors and Concurrency & Thread Safety
  • Notifications - LISTEN/NOTIFY, PgChannelListener, Flow-based receiving
  • Error Handling - Exception hierarchy, debugging
  • Type System - @PgEnum, @PgComposite, @DynamicallyMappable, dynamic_map projections, dynamic data insertion, Custom Type Handlers, GlobalTypeHandler, .options() per-query configs, standard type mappings

Architecture

Module Platform Description
api Multiplatform Common: Annotations & DTOs (JVM/JS). JVM-only: Query & Transaction interfaces.
core JVM Zero-dependency core engine. Pure JDBC & HikariCP.
spring-integration JVM Optional integration for Spring Boot (@Transactional support).
flyway-integration JVM Optional migration runner integration.

This library is legacy — superseded by octavius-postgresql.

About

Deprecated — superseded by octavius-postgresql. SQL-first data access layer for Kotlin & PostgreSQL on pgjdbc: fluent query builders, automatic type mapping (ENUM, COMPOSITE, ARRAY), transaction plans, polymorphic storage.

Topics

data-mappingdeprecatedjdbckotlinpostgresqlsql

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Apache-2.0 license
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