[Offline] JJUG Night Seminar: Robust Design Boundaries with Modern Java and an AI-Native Future

The July JJUG night seminar runs in two parts. The first is "How to build real design boundaries and escape vague layering". Drawing lines between a web layer, a use case layer, and a business logic layer can look orderly, but in many codebases DTOs pass straight through the layers, business rules scatter across procedures, and untrusted input flows onward in unguarded types. The lines are drawn, yet they protect nothing. Getting out of that state is the theme. The talk argues that the real boundary belongs where untrusted external data becomes a typed domain, and covers how to implement that boundary in Java. It uses Raoh, a decoder library built around this idea, to assemble code that converts untrusted input into domain types while returning failures as values, and contrasts the approach with Bean Validation. The design leans on records, sealed classes, and switch pattern matching from recent Java releases: by shutting out invalid data at the boundary, the inside of the domain stays as types and values. Yoshitaka Kawashima (@kawasima) of Wolf Chief speaks. The second session covers Java and AI related technology, with details to be updated once confirmed. The venue is Microsoft Japan in Shinagawa Grand Central Tower, running 19:00 to 21:00. Each session is 50 minutes, with an opening, a break, and a closing QA.