Developer rebuilds Seasar2 stack, logs the failures

The author starts from a familiar observation: tools like Claude Code and Codex can produce something plausible even for unfamiliar technology, which is convenient but may quietly remove the learning that comes from struggling. His own path into the craft—reading technical books, chasing certifications, copying code by hand, rebuilding environments from scratch, and searching for errors for a full day—is presented as something today's developers may no longer have the chance or time to do. Deliberately designing learning opportunities inside organizations, he suggests, may be one answer.

The experiment itself is an attempt to relive that struggle. The target is a Seasar2 setup from around ten years ago: a CentOS 5 container running on Docker on Ubuntu, with Java 1.5, Apache, Tomcat and Seasar2 installed directly rather than through compose. The writer is explicit that this is not a clean demo—the yum mirror error and the OpenSSL handshake failure are part of the story, and he explains how he probed the network, checked repository settings and eventually found a working mirror. He also notes that Seasar reached end of life in 2016 and receives no security patches, so it must not be exposed to the internet.

What the reader is meant to take away seems to be less the finished Hello World than the method: write down what you do not understand in each error, then ask AI not just for the fix but for its reasoning and for the knowledge gaps behind it. Whether that approach actually rebuilds the skills lost to convenient tooling is the open question the walkthrough leaves with the reader.