Use Spring Data read models

Add an integration

Choose the store used by the application:

// JPA
dependencies {
    implementation("io.cratis:arc-spring-data-jpa:<version>")
}

// MongoDB
dependencies {
    implementation("io.cratis:arc-spring-data-mongodb:<version>")
}

Both modules include the Arc Spring Boot starter and the corresponding Spring Data starter. Spring Boot continues to own the datasource, entity manager, Mongo client, repository discovery, and their standard configuration.

Inject a repository into a query

Spring Data repositories are ordinary Spring services. Mark a model-bound query dependency with @FromServices; Arc’s generated performer resolves the repository from the current application context.

Java

@Entity
@ReadModel
public class TaskView {
    @Id
    public String id;
    public String title;

    public static List<TaskView> all(@FromServices TaskViewRepository tasks) {
        return tasks.findAll();
    }
}

interface TaskViewRepository extends JpaRepository<TaskView, String> { }

View Java snippet source on GitHub

Kotlin

@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>

View Kotlin snippet source on GitHub

The same pattern works with MongoRepository, repository fragments, and application query services. An application bean replaces an auto-configured adapter bean of the same integration contract.

Then

Storing a domain concept, routing by tenant and streaming changes each need their own setup:

• Map JPA concepts — attribute converters and embedded ids.
• Map MongoDB concepts — concrete scalar pairs and identifiers.
• Repositories in queries and commands — paging, current state, tenant-bound access and transactions.
• Observable storage snapshots — change streams and JPA notifications.