1. Maven Dependencies & Project Structure 🏗️

Maven: Java's most popular build tool and dependency manager

Dependencies: External libraries our project needs

Spring Boot Starters: Pre-configured dependency bundles (websocket includes WebSocket + STOMP)

Transitive Dependencies: Maven automatically pulls in dependencies that our dependencies need

2. Spring Configuration Class ⚙️

WebSocketConfig.java - Key Java Concepts:

Annotations:

@Configuration  // Tells Spring: "This class contains configuration"
@EnableWebSocketMessageBroker  // Enables WebSocket messaging with STOMP

🧠 Java Learning:

Annotations: Metadata that provides information about code (like TypeScript decorators)

@Configuration: Spring stereotype annotation - marks a class as a source of bean definitions

Stereotype Annotations: @Configuration, @Service, @Controller, @Repository - tell Spring what role a class plays

Interface Implementation:

public class WebSocketConfig implements WebSocketMessageBrokerConfigurer

🧠 Java Learning:

Interface: Contract that defines what methods a class must implement

implements: Java keyword to implement an interface (like TypeScript implements)

Spring Configurers: Interfaces that let you customize Spring's behavior

Method Overriding:

@Override
public void registerStompEndpoints(StompEndpointRegistry registry) {
    registry.addEndpoint("/ws/lightning")
            .setAllowedOriginPatterns("*")
            .withSockJS();
}

🧠 Java Learning:

@Override: Annotation ensuring we're correctly overriding a parent method

Method Chaining: Builder pattern where each method returns this to chain calls

Registry Pattern: Spring uses registries to collect configuration

3. Data Transfer Objects (DTOs) 📦

Lombok Annotations:

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor

🧠 Java Learning:

Lombok: Library that generates boilerplate code at compile time

@Data: Generates getters, setters, toString, equals, hashCode

@Builder: Generates a builder pattern for object creation

@NoArgsConstructor: Generates empty constructor

@AllArgsConstructor: Generates constructor with all fields

Static Factory Method:

public static LightningWebSocketEvent from(Lightning lightning) {
    return LightningWebSocketEvent.builder()
            .eventId(UUID.randomUUID().toString())
            .timestamp(lightning.getCaptured())
            // ...
            .build();
}

🧠 Java Learning:

static: Method belongs to the class, not an instance

Factory Method: Design pattern for object creation

Builder Pattern: Readable way to create objects with many optional parameters

Method Chaining: Each builder method returns the builder for chaining

Validation Annotations:

@DecimalMin(value = "-90.0", message = "Latitude must be between -90 and 90")
@DecimalMax(value = "90.0", message = "Latitude must be between -90 and 90")
private Double latitude;

🧠 Java Learning:

Bean Validation: Java standard for validating object properties

Constraint Annotations: @DecimalMin, @DecimalMax, @Positive, @NotNull

Validation Messages: Custom error messages for validation failures

4. Advanced Java Features We Used 🚀

Conditional Logic in Utility Methods:

private static String calculateIntensity(Double peakCurrent) {
    if (peakCurrent == null) return "UNKNOWN";
    
    double absoluteCurrent = Math.abs(peakCurrent);
    
    if (absoluteCurrent >= 50000) return "EXTREME";
    if (absoluteCurrent >= 20000) return "HIGH";
    if (absoluteCurrent >= 5000) return "MEDIUM";
    return "LOW";
}

🧠 Java Learning:

static methods: Utility methods that don't need instance state

Wrapper vs Primitive: Double (object) vs double (primitive)

Null Safety: Always check for null with wrapper types

Math.abs(): Static utility method from java.lang.Math

Complex Conditional Logic:

private static String calculateRegion(Double latitude, Double longitude) {
    if (latitude == null || longitude == null) return "UNKNOWN";
    
    // Turkey approximate bounds
    if (latitude >= 35.0 && latitude <= 43.0 && longitude >= 25.0 && longitude <= 45.0) {
        if (longitude <= 32.0) return "TURKEY_WEST";
        if (longitude <= 38.0) return "TURKEY_CENTRAL";
        return "TURKEY_EAST";
    }
    // More conditions...
}

🧠 Java Learning:

Guard Clauses: Early return for invalid input

Logical Operators: && (AND), || (OR)

Nested Conditions: Organizing complex logic clearly

5. Spring Framework Patterns 🌿

Configuration over Convention:

registry.enableSimpleBroker("/topic", "/queue");
registry.setApplicationDestinationPrefixes("/app");
registry.setUserDestinationPrefix("/user");

🧠 Java Learning:

Spring Philosophy: Configure behavior explicitly

STOMP Protocol: Simple Text Oriented Messaging Protocol over WebSocket

Topic vs Queue: Pub/sub (topic) vs point-to-point (queue) messaging

Bean Lifecycle:

Spring creates our @Configuration class as a singleton bean

Spring calls our configuration methods during startup

Configuration is applied once and used throughout application lifecycle

6. Package Structure & Java Conventions 📁

co.iklim.services.backend.lightning/
├── config/         - Configuration classes
├── dto/           - Data Transfer Objects
│   └── request/   - Request DTOs
└── enumeration/   - Enums

🧠 Java Learning:

Package Naming: Reverse domain name convention

Separation of Concerns: Different types of classes in different packages

Maven Directory Structure: Standard layout that Maven expects

7. What Makes This Production-Ready Java 💪

Type Safety: Using proper types (Double vs String) and validation
Null Safety: Checking for null values before using them
Documentation: Comprehensive JavaDoc comments
Validation: Bean validation annotations for input validation
Builder Pattern: Makes object creation readable and safe
Factory Methods: Clean way to create objects with business logic
Configuration Separation: Config logic separated from business logic

8. Spring Boot Magic Happening Behind the Scenes ✨

When we start the application:

Component Scanning: Spring finds our @Configuration class
Auto-Configuration: Spring Boot automatically configures WebSocket based on our dependencies
Bean Creation: Spring creates instances of our configuration classes
Proxy Creation: Spring creates proxies for WebSocket handling
Endpoint Registration: Our endpoints become available at runtime