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Brew

Introduction

Brew is Kona’s reactive server-component product. You write a class with public state and actions, render HTML with Crema, and Brew keeps the browser in sync over a small JSON protocol—without a full page reload for every interaction.

(Brief nod: Brew occupies the same problem space as popular full-stack reactive component tools. The rest of this site describes Brew on its own terms.)

When to use Brew

Section titled “When to use Brew”

Use Brew when you want:

  • Server-owned state — form drafts, filters, pagination, and UI toggles live on the JVM.
  • Incremental HTML updates — the client morphs returned HTML into the existing DOM.
  • Kotlin and Java equally — the same component model, with first-class Java samples and tests.
  • Tight Crema integration — templates, layouts, and directives stay in one stack with Kona.

Prefer a JSON API + SPA when the UI is almost entirely client-driven and the server is only a data plane. Prefer plain Kona controllers + Crema when interactions are rare and full page responses are enough.

What you get

Section titled “What you get”
  1. A component class — public fields are state; public methods are actions the browser can call.
  2. A snapshot on the root HTML element (wire:snapshot, wire:effects, wire:id, wire:name).
  3. A client runtime that posts to POST /brew/update and morphs the new HTML into place.
  4. A bundled Alpine.js runtime — Brew ships Alpine 3.x plus plugins; you do not install Alpine separately for the default script tag.

How a click works

Section titled “How a click works”
  1. The browser finds the component root (wire:id) and reads wire:snapshot.
  2. It POSTs { _token, components: [{ snapshot, updates, calls }] } to /brew/update with the X-Brew header.
  3. The server verifies CSRF + checksum, restores state, runs the action, re-renders, and returns { components: [{ snapshot, effects }], assets }.
  4. The client morphs effects.html into the DOM (keyed by wire:key / wire:id).

Corrupt checksums or locked-property writes fail the request. Missing components or unknown actions raise Brew exceptions.

Relationship to Kona

Section titled “Relationship to Kona”

Brew is a separate artifact (org.konaframework:kona-brew) and a separate repository (konaframework/kona-brew). It depends on Kona HTTP, session, Crema, and related modules. Framework guides for routing, Crema, and grind live on the Kona docs site.

Next

Section titled “Next”