Java-TS-Gen

Problem

On a Java backend + TypeScript frontend, DTOs and interfaces drift. You change a record field, forget the frontend, and discover the mismatch at runtime. Manual sync is tedious and error-prone.

Approach

Java-TS-Gen (JTG) is a developer-time Maven plugin that scans for @TsRecord on Java records and emits TypeScript definitions next to the source.

• Annotation uses RetentionPolicy.SOURCE → zero runtime cost in production.
• Hooks into generate-sources (or mvn jtg:generate) so types regenerate on every normal build.
• Options for exportName and asType when frontend naming differs from the Java type.

@TsRecord
public record User(String name, int age, boolean active, UUID id) {}

Produces:

export interface User {
  name: string;
  age: number;
  active: boolean;
  id: string;
}

Stack

• Java annotation library (jtg-annotation, provided/optional scope)
• Maven plugin (jtg-maven-plugin) running at generate-sources
• Source-level parsing — no runtime classpath dependency on the generator

Outcomes

• Single source of truth for cross-boundary types: the Java record.
• Fits existing Maven workflows without a separate codegen service or heavy framework.
• Documented in a practical guide.

Design choice

Generate at build time, next to the source, rather than a remote schema registry or OpenAPI-only pipeline. That keeps the feedback loop inside the IDE and the familiar mvn compile path — the path of least resistance for day-to-day Java teams.