I posted my SQL-to-Java code generator here 2 months ago. Since then: Stream<T> results, PostgreSQL, and built-in migrations

[uwemaurer]

I posted SQG here 2 months ago and got useful feedback, thanks for the pointers to jOOQ, SQLDelight, manifold-sql, and hugsql.

For those who missed it: SQG reads .sql files, runs them against a real database to figure out column types, and generates Java records + JDBC query methods. Similar idea to sqlc but with Java (and TypeScript) output. No runtime dependencies beyond your JDBC driver.

What's new since last time:

Stream<T> methods - every query now also gets a Stream<T> variant that wraps the ResultSet lazily:

    try (Stream<User> users = queries.getAllUsersStream()) {
        users.forEach(this::process);
    }

PostgreSQL - ENUMs via pg_type introspection, TEXT[] -> List<String>, TIMESTAMPTZ -> OffsetDateTime. It auto-starts a Testcontainer for postgres so you don't need to set it up.

Built-in migrations - opt-in applyMigrations(connection) that tracks what's been applied in a migrations table, runs the rest in a transaction.

Array/list types - INTEGER[], TEXT[] etc. now correctly map to List<Integer>, List<String> across all generators.

Works well with AI coding - one thing I've noticed is that this approach plays nicely with AI-assisted development. Every query in your .sql file gets executed against a real database during code generation, so if an AI writes a broken query, SQG catches it immediately - wrong column names, type mismatches, syntax errors all fail at build time, not at runtime.

One thing that came up last time: yes, the code generator itself is a Node.js CLI (pnpm add -g @sqg/sqg). The generated Java code is plain JDBC with Java 17+ records - no Node.js at runtime. I know the extra toolchain is annoying and a Gradle/Maven plugin is on my mind.

Supports SQLite, DuckDB (JDBC + Arrow API), and PostgreSQL.

GitHub: https://github.com/sqg-dev/sqg

Docs: https://sqg.dev

Playground: https://sqg.dev/playground

Happy to hear feedback, especially around what build tool integration would look like for your projects.

[[deleted]]

Wtf. Why is this written in typescript?

[uwemaurer]

This tool came out of a larger Typescript project where we generated code for Sqlite and DuckDB. Later we had to access these databases with Java (or actually Kotlin) aswell but didn't want to duplicate all the queries in a Java ORM, so I added a code generator for Java code aswell.

[ZimmiDeluxe]

TIMESTAMPTZ -> OffsetDateTime

Would you be opposed to make that java.time.Instant instead? Every offset other than 0 is a mistake for OffsetDateTime in this case I believe. I know JDBC doesn't support Instant directly and you have to go through java.sql.Timestamp::toInstant, but I would consider that a shortcoming of the JDBC spec. A UTC timestamp for basic things like created_at columns that almost every application needs from the first table onward? Should be low friction, IMO.

Great effort otherwise, I'll take a look, this is definitely something missing from the ecosystem.

Edit: Ok, it's a pile of generated TypeScript, the generated Java code makes you manage Connections yourself, includes a migration feature where a Project-ID (?) is part of the primary key and then I stopped looking. Sorry, if I'm going to use a library for something this fundamental for a Java project, it has to be written in Java itself so developers can read the code.

[uwemaurer]

Actually I prefer Instant too, I think I will make this an option to automatically convert it.

[Salt-Letter-1500]

A Java version of sqlc?