Java and Kotlin

language = 'kotlin' generates the same model as Kotlin entities, services and controllers in src/main/kotlin, with the -kt edition of the chosen bundle (jpa-springboot-kt, ddd-springboot-kt, hexagonal-springboot-kt). The rules are shared; only how each language says it differs.

build.gradle

elasticore {
    architecture = 'hexagonal'
    language     = 'kotlin'       // java | kotlin
}

The same lifecycle in both languages

The Ticket of the Kotlin sample has two lifecycles, and its cancel command moves both:

blueprint/shop/model/ticket.yml (elasticore-template-kt)

  Ticket:
    meta: entity @root @expose(20) @owner(agentId) @access(read=owner, create=user, close=owner) @event(Closed) -- 작업

Kotlin (generated)

TicketBase.kt

    open fun cancel() {
        requireStatus("cancel", TicketStatus.OPEN)
        requireBilling("cancel", BillingStatus.UNBILLED)
        this.status = TicketStatus.CLOSED
        this.billing = BillingStatus.VOID
        raiseClosed()
    }

    /** Whether cancel may be given now: the status is OPEN and the billing is UNBILLED. */
    fun canCancel(): Boolean = (this.status == TicketStatus.OPEN) && (this.billing == BillingStatus.UNBILLED)

Java (the same rule)

ShipmentBase.java (the DSL guide's example)

public void cancel() {
    requireStatus("cancel", ShipmentStatus.READY);   // 1) every lifecycle is checked first
    requireFee("cancel", FeeStatus.PAID);
    this.status = ShipmentStatus.CANCELLED;          // 2) all pass, then all move
    this.fee = FeeStatus.REFUNDED;
    raiseCancelled();                                // 3) an event per target state, when declared
    raiseRefunded();
}

What differs

	Java	Kotlin
Event classes	fields + constructor + getters	vals of the primary constructor (data class)
Specifications	private constructor	object
Factories	private constructor + static	object + fun
Ports of domain services and process managers	@Autowired protected field on XxxBase	@Autowired protected lateinit var
Conditions	order.getItems()	order.items!!
Invariant listeners	@EntityListeners({A.class, B.class})	@EntityListeners(A::class, B::class)
Value objects	immutable through Lombok	immutable through the language
Sealed setters	@Setter(AccessLevel.PROTECTED)	protected set / final var ... private set
Signatures		nullability matches the service (save(dto: OrderDTO): OrderDTO?)

A rule that only one language has says so (requireSyntax) and stops with the reason when selected for the other - Java never ends up silently inside a .kt file.

What a Kotlin build needs

The Kotlin plugins a Kotlin JPA project applies, as in elasticore-template-kt (the sample takes the io.elasticore plugin from the repository itself; a project names the released version):

build.gradle

plugins {
    id 'org.jetbrains.kotlin.jvm' version '1.9.24'
    id 'org.jetbrains.kotlin.plugin.allopen' version '1.9.24'
    id 'org.jetbrains.kotlin.plugin.jpa' version '1.9.24'
    id 'io.spring.dependency-management' version '1.1.6'
    id 'io.elasticore' version '3.0.261022-rc1'
}

• org.jetbrains.kotlin:kotlin-reflect - a Kotlin application on Spring needs it.
• With Spring Boot 4: Kotlin 2.2 or later, and the Jackson Kotlin module is tools.jackson.module:jackson-module-kotlin.
• The generated code boots without the kotlin-spring plugin: extension services and repository adapters are open class, and entity collections are MutableList<X>.
• mapping: xml (JPA annotations moved to orm.xml): register io.elasticore.springboot3.entity.PersistentModel with allOpen and noArg.
• `in` - the hexagonal package adapter.in.web is written with the keyword escaped.

Where each reaches

Most rules reach both languages. @search(like) is case-insensitive in every Kotlin build (and in the v3 Java bundles); @restExclude removes methods from the Kotlin controller and use case while the Kotlin service keeps them.

Sample: elasticore-template-kt - generated, compiled and started on every build (ShopApiContractTest).