cratis-arc-spring-data-kotlin

Use Spring Data with JVM Arc

Keep Spring Data responsible for persistence and Arc responsible for the model-bound command/query pipeline. Repository injection alone does not isolate tenants or turn a repository into an observable source.

Verified product sources

Source: Arc.Kotlin: Integrations/SpringDataJpa, Integrations/SpringDataMongo (observable query services/extensions, contextual read-model providers, tenant access and converters) and Documentation/guides/spring-data/*.mdx. Add io.cratis:arc-spring-data-jpa:<version> or io.cratis:arc-spring-data-mongodb:<version>; both include the Arc Spring Boot starter and corresponding Spring Data starter. Spring owns repository discovery, datasource/entity manager, Mongo client and their standard configuration.

Query a mapped read model

JPA example (requires the application's normal JPA entity/no-arg setup):

// Copyright (c) Cratis. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

import io.cratis.arc.artifacts.FromServices
import io.cratis.arc.artifacts.ReadModel
import jakarta.persistence.Entity
import jakarta.persistence.Id
import org.springframework.data.jpa.repository.JpaRepository

@Entity
@ReadModel
data class TaskView(@Id val id: String = "", val title: String = "") {
    companion object {
        @JvmStatic
        fun all(@FromServices tasks: TaskViewRepository): List<TaskView> = tasks.findAll()
    }
}

interface TaskViewRepository : JpaRepository<TaskView, String>

The same injection pattern works with MongoRepository, fragments or an application query service. Java uses static query methods on its mapped type. Protect the query with the application's authorization policy; mapping does not make it safe to expose anonymously.

A query can declare exact non-null Spring Data Commons Pageable and Sort. KSP binds them from the captured QueryRequest, not thread-local request scope. Such queries must return exact org.springframework.data.domain.Page<T>; Arc normalizes it into QueryPage<T> before renderers, preserving pre-page total count. Page size zero means unpaged; blank sort field means unsorted. Do not confuse Spring Data Page<T> with a nonexistent Arc Page<T>.