⚙️ Configuration

Sprout uses a YAML-based configuration system that's loaded at startup. The AppConfig class handles parsing and provides convenient access to configuration properties.

Configuration File

Create src/main/resources/application.yml in your project:

author: your-name

server:
  execution-mode: hybrid   # nio | hybrid | blocking (default: hybrid)
  thread-type: virtual     # virtual | platform (default: virtual)
  thread-pool-size: 150    # used when thread-type = platform

sprout:
  database:
    url: jdbc:mysql://localhost:3306/sprout
    username: root
    password: change-me

  security:
    enabled: true
    jwt:
      secret: your-jwt-secret-key
      expiration: 86400  # 24 hours in seconds

Server Configuration

Execution Modes

Sprout supports three execution modes to suit different use cases:

Mode	HTTP Handler	WebSocket	Use Case
nio	NIO selector	NIO	High concurrency, low memory
hybrid	Virtual/platform pool	NIO	Production (recommended)
blocking	Platform threads	N/A	Debugging/learning

NIO Mode

server:
  execution-mode: nio

• Single-threaded selector loop for all I/O
• Most memory-efficient for high connection counts
• Best for I/O-bound applications

Hybrid Mode (Recommended)

server:
  execution-mode: hybrid
  thread-type: virtual

• HTTP requests handled by virtual threads or platform pool
• WebSocket connections handled by NIO selector
• Best balance of performance and resource usage

Blocking Mode

server:
  execution-mode: blocking
  thread-type: platform
  thread-pool-size: 200

• Traditional one-thread-per-request model
• Easiest to debug and understand
• WebSocket not supported in this mode

Thread Types

Choose between virtual threads (Project Loom) and traditional platform threads:

Type	When to Use	Configuration
virtual	Default choice (recommended)	thread-type: virtual
platform	When you need bounded concurrency	thread-type: platform + thread-pool-size

server:
  thread-type: virtual  # Unlimited virtual threads

server:
  thread-type: platform
  thread-pool-size: 150  # Fixed-size thread pool

Database Configuration

Configure your database connection:

sprout:
  database:
    url: jdbc:mysql://localhost:3306/myapp
    username: myuser
    password: mypassword

CORS Configuration

cors:
  allow-origin: "*"
  allow-credentials: true
  allow-methods: "GET, POST, PUT, DELETE, OPTIONS"
  allow-headers: "Content-Type, Authorization"
  expose-headers: ""
  max-age: 3600

Accessing Configuration in Code

Use AppConfig to access configuration values.

@Component
public class MyService {
    private final AppConfig config;

    public MyService(AppConfig config) {
        this.config = config;
    }

    public void doSomething() {
        String author = config.getStringProperty("author");
        int poolSize = config.getIntProperty("server.thread-pool-size", 100);
        boolean securityEnabled = config.getBooleanProperty("sprout.security.enabled", false);
    }
}

Configuration Validation

Sprout validates configuration at startup and provides helpful error messages:

// Invalid configuration will cause startup failure
server:
  execution-mode: invalid-mode  # Error: Unknown execution mode
  thread-pool-size: -1          # Error: Pool size must be positive