An Introduction to DataHandler internals

DataHandler is the most critical — and complex — class in TYPO3 Core. At around 10,000 lines of code, it's a legacy beast that handles the majority of data operations in the backend, supported by thousands of tests focused on relations, language handling, and workspace integrity.

This talk explores the current state of the codebase and the ongoing efforts to refactor it. We'll dive into questions like: What does DataHandler actually do, and why is it so important? What does the public API look like, and how is the structure evolving?

We'll talk about why we chose to refactor instead of rewriting from scratch, go over the main pain points, and share some refactoring strategies that work well in such scenarios.

Whether you're curious about TYPO3 internals, planning to contribute, or just enjoy tales of refactoring legacy code, this talk will give you a deeper understanding of one of the framework’s most central components.