🚗 Vehicle Engine Factory (Spring Core Project)

A simple Spring Core (Java-based configuration) project demonstrating the use of FactoryBean to dynamically create different types of engine objects (Diesel, Electric, Hybrid) based on external configuration.

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📌 Overview

This project showcases how to:

• Use Spring's FactoryBean interface to control object creation.
• Externalize configuration using application.properties.
• Achieve loose coupling via interfaces and dependency injection.
• Dynamically switch implementations without changing code.

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⚙️ Tech Stack

• Java
• Spring Core (Annotation-based configuration)
• Maven (optional, if you add build support)

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📂 Project Structure

com.nit
│
├── config
│   └── AppConfig.java
│
├── factory
│   └── VehicleEngineFactoryBean.java
│
├── sbeans
│   ├── Engine.java
│   ├── DieselEngine.java
│   ├── ElectricEngine.java
│   └── HybridEngine.java
│
└── main
    └── TestApp.java

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🧠 Core Concept

Instead of directly creating objects using new, we let Spring decide which engine to create at runtime using a custom FactoryBean.

🔑 Key Logic

• The engine type is read from properties:

  engine.type=diesel

• Based on this value, the factory returns the correct implementation:

if(engineType.equalsIgnoreCase("electric")) {
    return new ElectricEngine();
}
else if(engineType.equalsIgnoreCase("diesel")) {
    return new DieselEngine();
}
else if(engineType.equalsIgnoreCase("hybrid")) {
    return new HybridEngine();
}

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📁 Important Files

🔹 Configuration Class

• Loads properties and configures the FactoryBean

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🔹 FactoryBean Implementation

• Central place where object creation logic exists

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🔹 Engine Interface

• Common contract for all engine types

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🔹 Engine Implementations

• Diesel Engine →
• Electric Engine →
• Hybrid Engine →

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🔹 Main Class

• Bootstraps Spring container and runs the app

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▶️ How to Run

1. Clone the repository

2. Open in your IDE (Eclipse / IntelliJ)

3. Set engine type in application.properties:

   engine.type=electric

4. Run:

   TestApp.java
   

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🔄 Output Example

If engine.type=diesel

DieselEngine has started.
DieselEngine has stoped.

If engine.type=electric

ElectricEngine has started.
ElectricEngine has stoped.

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🎯 Why This Matters

This pattern is super useful when:

• You want runtime flexibility
• You want to follow SOLID principles
• You need clean separation of object creation logic

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🚀 Future Improvements

• Add Spring Boot support
• Use profiles instead of properties
• Add logging framework (SLF4J / Logback)
• Introduce dependency injection into engines

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📜 License

This project is for educational purposes.

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💡 Final Thought

Small project, but the concept? 🔥 Understanding FactoryBean gives you real control over how Spring creates and manages objects — that’s where things start getting powerful.

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