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Java 8／11からJava 21／27へ — 移行のメリット、難所、現実的な進め方

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Avatar for Daisuke Masuda Daisuke Masuda PRO
October 18, 2026
Programming
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Java 8／11からJava 21／27へ — 移行のメリット、難所、現実的な進め方

https://daisuke.masuda.tokyo/article-2026-19-18-1954

本資料は、Java 8／11で稼働する既存業務システムをJava 21／25／27へ移行する際の判断材料を整理したものです。JDK更新、ビルド環境、依存ライブラリ、フレームワーク、アプリコードを別の作業として捉え、Java 8起点と11起点の違い、内部API、文字コード・TLSなどの動作変化、運用基盤を解説します。Java 21と25はLTS、27はnon-LTSであり、保守条件はベンダーと契約に依存します。Tomcat 9のjavax系とTomcat 10.1／11のjakarta系も区別し、検証、段階展開、ロールバックまでの実践的な移行手順を示します。

Avatar for Daisuke Masuda

Daisuke Masuda PRO

October 18, 2026

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