Simon Martinelli

The recording of my Spring I/O 2026 talk is now online 🎥 Spec-driven Development: How AI Changed Everything (And Nothing) AI is changing how we build software. But one thing has not changed: unclear requirements still lead to unclear software. In this talk, I show why specs become even more important when we use AI coding agents. The better we describe the intended behavior, the better AI can help us implement, test, and evolve the system. I also explain how the AI Unified Process uses: - Requirements Catalog - Entity Model - System Use Cases - Traceability from specs to code and tests The goal is not to replace developers. The goal is to give AI the right context, so developers can focus more on design, review, and domain correctness. Recording: youtube.com/watch?v=35dH6q… Thanks to Spring I/O for publishing the recording. #SpringIO #AI #SoftwareDevelopment #SpecDrivenDevelopment #Java #SpringBoot #Architecture #AIUnifiedProcess

@filipSk @oliverjaun Name some of your high profile startups

@oliverjaun @simas_ch Uber was founded 2009, Airbnb 2008, so.. thank you for validating that point 😂

IMO Java, Vaadin, jOOQ, and Spring Boot are the best choices for AI-driven software development.

The title is a bit misleading. It doesn’t mean that you should prefer skills over MCP. It means that an MCP server can serve skills. That would also solve skill distribution but opens security problems like prompt injection because you don’t have the skills installed locally and can’t review it

Skills over MCP aaif.io/blog/skills-ov…

From Prompt to Java Chart in Seconds 🚀 youtube.com/shorts/Q1RC_EH… via @YouTube

@vlad_mihalcea 💯 but I don't review all code anymore

@simas_ch While AI can use any stack, and many times it loves Python, I choose the stack that I know best so that I can review the AI-generated code.

@filipSk Well startups are also a niche compared with the enterprise environment, where Java has been the #1 for many years.

@simas_ch Among high-profile startups founded since 2021, Java appears to be a niche greenfield choice rather than a mainstream default. This world.

@bwilmsmann Well, I try not to rely on the model but on the harness. Vaadin and jOOQ have MCPs and skills that help the agent a lot. I can achieve the same results with a local model as I can with one of the frontier models. (only way slower but this is the problem of my local hardware.,

@simas_ch Moreover, the same argument made for Java in terms of AI applies here as well. The corpus for AI to draw upon is larger by several orders of magnitude for HTML and SQL than for Vaadin and jOOQ.

@filipSk Which world?

@simas_ch The world does not agree, the world usually is right in the long run

@sivalabs Well, the type of the application certainly matters. In my case, I have no application that is not a good fit for Vaadin, except for a simple website that requires SEO. "Resource Driven Development" is probably the best way, as technical knowledge can be learned and shared.

@simas_ch What happened to "which technologies to use depends on what type of application you are building" and "The best tech stack is what your team knows very well" 😀

@asm0di0 My point is that Vaadin already did the job for you. There are certainly other component libraries that did for sure. But if you do it by yourself there is more work than you think.

Look, wai-aria is covered incredibly good in the web. And computers are very good in it, no need to friend on one particular framework here. I'm not saying that vaadin is bad, I'm saying that other solutions are not worse and sometimes may be even better, especially when you don't need to write the code yourself, only understand it

@lofidewanto Absolutely. My point is don’t split things that belong together. SCS contains UI, logic, data. The agent will implement everything at once. Splitting frontend and backend are a Conaway reverse maneuver.

@simas_ch We don’t have a clear definition of the word micro. What does micro actually mean? 10K LoC? SCS doesn’t define the size at all, it’s intentionally generic. A DDD BC is subjective in terms of size. It can be micro or even nano, depending on how you define its boundaries.

„Monolith“ is not good for AI agents. „Microservice“ is good for AI agents.

@asm0di0 I think you should read about what accessibility means. Also here, Vaadin got you covered: vaadin.com/accessibility

They scale horizontally; the only component potentially missing is a queue, like RabbitMQ or ActiveMQ. I would say that machines are much better at accessibility than me. If you're saying that it also needs a high-contrast theme — you're probably right, and it should be simple to do. If you're talking about scalability like in "visual scalability" — this is where daisyUI shines — a lot of components, all styled the same. Nothing will prevent you from using the same theme for it across all the applications. It's a matter of unification, not of the choice of a particular technology.

@danielbartl @apache_wicket That's another category because they also must be SEO-friendly. And in that case plain HTML is still the best way to go.

@simas_ch @apache_wicket Fair enough! They do not have to be extensive if they are component based though. For consumer facing apps like online shops + product catalog views might be really handy having HTML templates (& SSR). But these are not classic business apps I guess.

@lofidewanto Why? If you build self-contained systems, you neither need microfrontends nor microservices. If you split your application according to DDD bounded contexts, you end up with self-contained systems.

@simas_ch Microfrontends are the frontend counterpart to microservices. I hope this is already the standard today… github.com/gwtboot/microf… … already 4 years ago… 😅

@asm0di0 The point with business applications is scaling. So what would you do if you had to create 50 of them that must all look the same, and the components must behave the same? And the apps must be accessible according to EU and US regulations?

@simas_ch I am not sure about definitions; would you call this a business application? asm0dey.github.io/calit/ I would; it works like Calendly, which is used by businesses. It has Google and OIDC integration. And probably even has the potential to be connected to things like Stripe…

@danielbartl @apache_wicket Tbh I don’t want to deal with HTML when I create business applications. It’s not the right abstraction. Extensive HTML template are also hard to review

@simas_ch Great stack! Full stack open source Java alternative when SSR is preferred: @apache_wicket with a simple CSS library like Oat (oat.ink) + Spring etc. Also a great platform for building lightweight components and applications. Wicket templates are pure HTML.

@asm0di0 Well, if you use Qute without JavaScript, then you will not have rich components but just templates. If you build a website or a tool that's probably fine, but if you are building business software where you have a lot of application you need a design system with rich components.

@simas_ch Claude is extremely good in designing components or using existing ones from, for example, daisyui, which even has its own skill :) And there's so much web experience in LLM, that it turns out great (in my opinion).

@asm0di0 Well, Qute has no components. martinelli.ch/component-mode…

@simas_ch Or, for example, Quarkus, jOOQ, and Qute...

Wie wird aus einer guten Idee ein System, das von AI zuverlässig umgesetzt werden kann? Am 8. September 2026 zeige ich an den Workshop-Tagen von CH Open, wie Spec-driven Development mit dem AI Unified Process funktioniert. Im ganztägigen Workshop arbeiten wir uns durch den gesamten Ablauf: • Anforderungen und Use Cases präzisieren • das Entity Model als gemeinsame fachliche Sprache entwickeln • Architekturentscheidungen ableiten • Tests aus den Spezifikationen entwickeln • die Umsetzung mit AI unterstützen Der entscheidende Punkt: Nicht der Prompt steuert die Entwicklung, sondern eine konsistente und nachvollziehbare Spezifikation. 📅 Dienstag, 8. September 2026 🕘 09:00 bis 17:00 Uhr 📍 OST Ostschweizer Fachhochschule, Campus Rapperswil 🎟️ Anmeldung: eventfrog.ch/de/p/wissensch… Ich freue mich auf einen intensiven Tag mit vielen praktischen Beispielen, Diskussionen und Austausch. #SpecDrivenDevelopment #AIUnifiedProcess #SoftwareArchitecture #RequirementsEngineering #SoftwareTesting #ArtificialIntelligence #OpenSource

@sfreund Because you stay in a single ecosystem, Vaadin has great components, is super secure, and has skills and MCP server for agents. The model is not that important, it’s the harness.

@simas_ch Why is Vaadin better than Angular? Models have of course vastly more training data on TS frameworks.