Java Interoperability

DSL Generation Note

KSP generates the type-safe DSL in a module with Kotlin in it; a Java module gets it from the annotation processor, drivine4j-codegen-java:

• Your @GraphView and @NodeFragment classes can be in Java or Kotlin
• At runtime, both Java and Kotlin classes work fully with the object manager

Recommended Pattern

Best Practice: Define @GraphView classes in Kotlin, everything else can be Java.

// Java fragments work great!
@NodeFragment(labels = {"Person"})
public class Person {
    @NodeId public UUID uuid;
    public String name;
    public String bio;
}

A fragment may extend a Java base class that keeps its fields private, @NodeId private String id; among them: they are the fragment’s state, saved and loaded with its own, and the base’s schema annotations, such as @Unique, are declared. A field the subclass declares again, @GraphTransient or not, hides the base’s. A Kotlin base class’s private properties are not stored, as Kotlin’s reflection leaves them out.

// A GraphView in Kotlin gets its DSL from KSP; one in Java, from drivine4j-codegen-java
@GraphView
data class PersonContext(
    @Root val person: Person,  // References Java class!
    @GraphRelationship(type = "WORKS_FOR")
    val worksFor: List<Organization>
)

// Use from Java with the fluent DSL API
List<PersonContext> results = JavaQueryBuilderKt
    .query(graphObjectManager, PersonContext.class)
    .filterWith(PersonContextQueryDsl.class)
    .where(dsl -> dsl.getPerson().getName().hasSubstring("Alice"))
    .loadAll();

Summary

Feature	Java Support	Notes
@NodeFragment	✅ Full	Works identically in Java and Kotlin
@RelationshipFragment	✅ Full	Works identically in Java and Kotlin
@GraphView runtime	✅ Full	Loading, saving, polymorphism all work
Type-safe DSL	✅ Full	Use filterWith() API from Java
instanceOf()	✅ Full	Filter by @NodeFragment subtype
DSL generation	✅ Full	KSP for Kotlin modules, drivine4j-codegen-java for Java ones
Generic collections	✅ Full	Java reflection handles List<T>, Set<T>
Polymorphic types	✅ Full	Works with sealed classes or @JsonSubTypes