persistence-graph-extraction-jooq

Demonstrates how to assemble an object graph from a relational database using jOOQ (DSLContext) and MULTISET without ORM or pagination.

What it shows

• Assembling a three-level object graph (Owner → Pet → Visit) using jOOQ MULTISET nesting
• Using package-private class as an encapsulation boundary inside the infrastructure layer
• Two query strategies:
  • full graph — Owner with Pets and Visits (OwnerView)
  • flat list — Owner with pet names only (OwnerListView)

Stack

• Java 25
• Spring Boot
• jOOQ (DSLContext)
• H2 (in-memory database)

Structure

application/
    OwnerReadRepository       # port (interface)
    view/                     # read models: OwnerView, OwnerListView, PetView, VisitView

infrastructure/
    JooqOwnerReadRepository   # jOOQ implementation (package-private)

Key idea

jOOQ MULTISET assembles the object graph directly in SQL — no flat rows, no deduplication, no intermediate projection classes:

Owner(jack)
  └── Pet(buddy1)
        ├── Visit(2026-01-10)
        └── Visit(2026-02-15)
  └── Pet(buddy2)
        └── Visit(2026-03-01)

A single DSL query with nested MULTISET expressions returns the fully structured result, mapped directly into view records via Records.mapping().

Compare with the JDBC and JPA + Blaze approaches:

	JDBC	jOOQ	JPA + Blaze
SQL result	flat rows (cartesian JOIN)	nested collections	optimized per-view query
Deduplication	LinkedHashMap in projections	not needed	not needed
Intermediate classes	OwnerProjection, PetProjection, etc.	none	@EntityView interfaces
Mapping	ViewMapper	Records.mapping()	ViewMapper
N+1 problem	no (single JOIN query)	no (single query)	no (Blaze optimizes automatically)

No ORM, no JSON parsing — just jOOQ and a single query.

JooqOwnerReadRepository is package-private by design; only OwnerReadRepository (the interface) is exposed outside the infrastructure package.

Tests

Integration tests in src/test/java cover graph assembly, flat list extraction, and edge cases.

Related

• persistence-graph-extraction-jdbc — same approach with plain JDBC
• persistence-graph-extraction-jpa — same approach with JPA + Blaze Persistence
• persistence-graph-pagination-jdbc — same approach with pagination support

Run

./mvnw spring-boot:run