Concepts

These are the core building blocks of Mateu. Understanding them lets you build any UI the framework supports.

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What Mateu does

Mateu turns a plain Java class into a running UI. Fields become form state. Annotated methods become actions. Routes are declared with @UI and @Route. The framework handles everything between.

The request cycle is stateless: each request instantiates the ViewModel, hydrates it with URL and form data, executes the requested action, and discards the object.

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Recommended reading order

1. State, actions and fields — fields, controls, actions, return types
2. Execution model — the stateless request cycle
3. ViewModel lifecycle — instantiate → hydrate → execute → respond
4. Routing and parameters — path params, query params, URL binding
5. UI vs Route — @UI vs @Route and how they compose
6. Field stereotypes — overriding inferred controls with @Stereotype
7. Validation — Bean Validation annotations in the UI
8. Action behavior — @Button, @Toolbar, @Action, row-level actions
9. UI effects — what actions can return and what each type does
10. Declarative vs fluent — when to use annotations vs the builder API

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What you will learn

These concepts explain how Mateu:

• turns a Java class into a rendered form
• maps URL parameters to ViewModel fields
• executes actions inside a stateless lifecycle
• sends effects back to the browser (messages, navigation, state updates)
• lets you override inferred rendering with stereotypes
• validates input using standard Bean Validation