Kotlin on Jamie Craane personal blog

Multi-Tenancy With Postgres Row-Level Security in Ktor

Thu, 09 Jul 2026 00:00:00 +0000

Introduction

Moxie IT (the company I co-own) developmed a time tracking and invoicing tool called MinuteMint as an alternative to Harvest. It runs in production and supports multi-tenancy from the first migration: every client, project, time entry and invoice belongs to exactly one tenant.

That raises a question you have to answer on day one, because it is expensive to answer later:

Where does tenant isolation actually live?
What happens when a developer forgets to apply it?
How do you prove, in a test, that a tenant cannot see another tenant’s rows?

The default answer in most codebases is “in the query”. I think that is the wrong place.

Bridging Human Intent and AI Code Generation with @AIGuideline

Mon, 13 Oct 2025 00:00:00 +0000

Introduction

As AI-powered coding assistants become increasingly prevalent in software development, a new challenge emerges: how do we ensure that AI-generated code aligns with our project’s specific architectural patterns, design principles, and coding standards?

Existing AI guidelines, for example junie/.guidelines exist for this purpose. However, they are often large and challenging to maintain. Depending on the project, they can also contain a lot of information. The larger the guidelines file, the harder for the AI to follow consistently.

Integrating Firebase auth in server side Thymeleaf app

Thu, 12 Jun 2025 00:00:00 +0000

This blog post explains how to implement server-side authentication with Firebase in a Kotlin Ktor application using Thymeleaf templates. This approach is particularly useful for admin panels or dashboards where you want to leverage Firebase Authentication while rendering server-side HTML. By leveraging Thymeleaf (or other server-side templates for example Freemarker), may shorten the time-to-market for these kind of dashboard compared to full fledged Javascript frameworks like Angular or React.

Integrating Firebase JWT token verification in Ktor - Part 2

Wed, 15 Jan 2025 00:00:00 +0000

Part 2: Integrating Firebase Users into Your Database with Ktor

In the first part of this blog series, we explored how to integrate Firebase JWT authentication into your Ktor application. Besides creating accounts and logging in, we also want to store a reference of the Firebase user in our own database. This way, data can be associated with a specific user.

In this post, we will look at how to integrate your Firebase users in your own application database. This article will cover using custom tokens, context receivers, and the Exposed SQL library to implement this functionality.

AI Assistant Prompt Catalog

Wed, 11 Dec 2024 00:00:00 +0000

AI Assistant prompt catalog

Prompts

Android: Replace kotlin synthetic view viewBinding

@author: https://x.com/jcraane

Kotlin synthetics are deprecated. This prompt replaces Kotlin synthetics in a file with viewBinding:

Replace kotlin synthetic with viewBinding.

Prefix all Koltin synthetic views with binding.

Replace snake case view names with camel casing.

$SELECTION

Create a unit test using Kotest and BehaviorSpec

@author: https://x.com/jcraane

You are an expert AI programmer which uses unit tests to verify behavior.

- Use Kotlin kotest BehaviorSpec
- Write unit tests for the obvious cases
- Write unit tests for the edge cases
- DO NOT EXPLAIN THE TEST
    
$SELECTION

Create a unit test using Jest

@author: https://x.com/jcraane

Integrating Firebase JWT token verification in Ktor - Part 1

Wed, 11 Dec 2024 00:00:00 +0000

Integrating Firebase JWT token verification in Ktor - Part 1

As applications become more complex and security becomes a priority, choosing the right tools to handle authentication is crucial. Today, we’ll explore how to integrate Firebase JWT (JSON Web Token) authentication in a Ktor server application. This blog post will cover the core setup and implementation details required to ensure secure handling of JWTs in a Ktor application.

Introduction to Ktor and Firebase Authentication

https://ktor.io is a lightweight framework for creating web applications in Kotlin, known for its simplicity and flexibility, you will find no magic here. Firebase Authentication provides backend services, easy-to-use SDKs, and ready-made UI libraries to authenticate users to your app. It supports authentication using passwords, phone numbers, and popular federated identity providers like Google, Facebook, and Twitter.

Kotlin: Multi variable null check

Thu, 10 Dec 2020 00:00:00 +0000

Although not-null, immutable variables with sensible defaults are often desired, it is not always the case. It is sometimes required to check if multiple variables are not null. This post describes several variants of how to do this when smart casts are not possible because the variables are mutable.

Consider the following example:

class Person() {
    var name: String? = null
    var age: Int? = null

    fun doSomething() {
        if (name != null && age != null) {
            name.length // Compile error since smart-cast is not possible
        }
    }
}

When the name or age property is accessed after the above null check we get the following compile error: smart cast to ‘String’ is impossible, because ’name’ is a mutable property that could have been changed by this time.

Kotlin on Jamie Craane personal blog

Multi-Tenancy With Postgres Row-Level Security in Ktor

Introduction

Bridging Human Intent and AI Code Generation with @AIGuideline

Introduction

Integrating Firebase auth in server side Thymeleaf app

Server-Side Login with Firebase in Thymeleaf Templates

Integrating Firebase JWT token verification in Ktor - Part 2

Part 2: Integrating Firebase Users into Your Database with Ktor

AI Assistant Prompt Catalog

AI Assistant prompt catalog

Prompts

Android: Replace kotlin synthetic view viewBinding

Create a unit test using Kotest and BehaviorSpec

Create a unit test using Jest

Integrating Firebase JWT token verification in Ktor - Part 1

Integrating Firebase JWT token verification in Ktor - Part 1

Introduction to Ktor and Firebase Authentication

Kotlin: Multi variable null check