Vaadin Signal API Use Cases

This repository contains a collection of Vaadin views demonstrating the Signal API for reactive state management.

Overview

The Vaadin Signal API provides reactive state management for Vaadin Flow applications. This project contains 29 implemented use cases (23 single-user + 6 multi-user) showcasing various signal patterns and real-world UI scenarios.

Use Cases

Single-User Use Cases

1. Dynamic Button State - Form validation with reactive button enable/disable
2. Progressive Disclosure - Nested conditional form sections
3. Interactive SVG Shape Editor - Dynamic SVG manipulation with extensive attribute binding
4. Filtered Data Grid - Client-side filtering and sorting
5. Cascading Selector - Dependent dropdown menus (country → state → city)
6. Shopping Cart - Real-time cart totals and item management
7. Multi-Step Wizard - Form wizard with validation and navigation
8. Form with Binder Integration - Vaadin Binder with signal-based validation
9. Responsive Layout - Window size as signal for responsive UI
10. Current User Signal - Application-wide user context from Spring Security
11. Async Data Loading - Loading/success/error states for async operations
12. Debounced Search - Search-as-you-type with 300ms debouncing
13. URL State Integration - Query parameters as signals with router integration
14. Custom PC Builder - Complex state at scale with ~70 interdependent signals
15. LLM-Powered Task Management - AI assistant with real-time chat interface
16. Parallel Data Loading - Per-item loading states with individual spinners
17. User Preferences - Session-scoped signal for user settings
18. Signals-Based i18n - Reactive internationalization with ResourceBundles
19. Two-Way Mapped Signals - Bidirectional field-to-record binding
20. Real-time Dashboard - Interactive dashboard with charts and live metrics
21. VirtualList Notifications - Notification inbox with VirtualList bound to signal data source

Multi-User Collaboration (6 total)

1. Shared Chat - Collaborative message list with append-only operations
2. Collaborative Cursors - Real-time cursor position sharing
3. Click Race Game - Conflict resolution and atomic operations
4. Collaborative Editing - Field-level locking for concurrent form editing
5. Shared Task List - Real-time collaborative task management with inline editing
6. Shared LLM Task List - Multi-user LLM-powered task management with chat

Project Structure

src/main/java/com/example/
├── usecase01/                       # UC01-UC23 (one package per use case)
│   └── UseCase01View.java
├── usecase02/ ... usecase23/
├── muc01/                           # MUC01-MUC07 (one package per use case)
│   ├── MUC01View.java
│   └── MUC01Signals.java           # Per-MUC shared signal class
├── muc02/ ... muc07/
├── security/
│   ├── CurrentUserSignal.java       # Application-scoped user context signal
│   ├── SecurityConfiguration.java   # Spring Security setup
│   └── SecurityService.java
├── service/                         # Shared services (analytics, data loading)
├── signals/
│   ├── UserSessionRegistry.java     # Active user tracking
│   ├── UserInfo.java
│   └── SessionIdHelper.java
├── preferences/
│   └── UserPreferences.java         # Session-scoped user preferences
├── listeners/
│   └── UserInteractionTracker.java
├── views/
│   ├── MainLayout.java              # App layout with navigation
│   ├── LoginView.java               # Login page
│   ├── HomeView.java                # Landing page
│   └── ActiveUsersDisplay.java
└── MissingAPI.java                  # Helper methods for signal bindings

Running the Application

1. Prerequisites: Java 25+, Maven 3.9+
2. Build: mvn clean install
3. Run: mvn spring-boot:run
4. Access: Open http://localhost:8080

Login Credentials

• viewer / password (VIEWER role)
• editor / password (EDITOR role)
• admin / password (ADMIN role)
• superadmin / password (SUPER_ADMIN role)

Key Patterns Demonstrated

Basic Reactivity

• One-way and two-way bindings
• Computed/derived signals
• Signal transformations with map()

UI Patterns

• Conditional rendering (bindVisible, bindEnabled)
• Dynamic text content (bindText, bindElementText)
• Responsive layouts (browser window size as signal)
• Form validation with signals

Advanced Patterns

• Vaadin Binder integration with signals
• Application-scoped signals (Spring @Component)
• Multi-user collaboration with shared signals
• Browser integration (window size, page title)
• Spring Security integration

MissingAPI Helpers

Since the official Signal API is still in development, MissingAPI.java provides temporary helper methods for bindings not yet in the framework:

• bindItems() - List binding for Grid/ComboBox (multiple overloads for Signal, ListSignal, SharedListSignal)
• bindBrowserTitle() - Browser document title binding
• bindInvalid() - Component invalid state binding
• tabsSyncSelectedIndex() - Bidirectional Tabs selected index synchronization

Multi-User Architecture

Multi-user use cases (MUC 01-04, 06-07) demonstrate collaborative features using:

• Per-MUC Signal Classes - Each MUC has its own application-scoped Spring component (MUC01Signals, MUC02Signals, MUC03Signals, MUC04Signals, MUC06Signals, MUC07Signals) holding shared signals
• UserSessionRegistry - Tracks active users with reactive signal
• onAttach/onDetach - Lifecycle hooks for user registration

All users see real-time updates via Vaadin's automatic UI synchronization.

Documentation

• signal-use-cases.md - Detailed descriptions and patterns for all 29 use cases

Technical Stack

• Vaadin 25.1-SNAPSHOT - Web framework with Signal API
• Spring Boot 4.0.1 - Application framework
• Spring Security - Authentication and authorization
• Java 25 - Language and platform
• Maven - Build tool

Related Resources

• Vaadin Signal API Proposal
• Vaadin Flow Documentation
• Spring Security with Vaadin

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Status: Active development Last Updated: 2026-02-16 Total Use Cases: 29 (23 single-user + 6 multi-user)