What is Dependency Injection in Spring?

September 01, 2025

Best Full Stack Java Training Institute in Hyderabad with Live Internship Program

Are you aiming to build a strong foundation in software development and land your dream job in the IT industry? Look no further than Quality Thought, the best Full Stack Java training institute in Hyderabad, known for its industry-focused training and valuable live internship program.

Quality Thought’s Full Stack Java course is designed for both beginners and professionals who want to master the skills required to develop real-world web applications. The course covers everything from Core Java, Advanced Java, JDBC, Servlets, JSP, Spring, Spring Boot, Hibernate, to front-end technologies like HTML, CSS, JavaScript, Bootstrap, Angular, and React.

What makes this training truly effective is the live internship, which provides hands-on experience on real-time projects. Students work in a simulated industry environment, dealing with actual coding tasks, debugging, deployment, version control, and team collaboration. This practical exposure helps learners build confidence and problem-solving skills—critical assets in any software job.

Program Highlights:

Comprehensive Full Stack Java Curriculum

Real-Time Projects with Live Internship

Mentorship from Industry Experts

Daily Practice, Assignments & Project Work

Resume Preparation, Mock Interviews & Placement Assistance

Internship Certificate & Career Guidance

Whether you're a fresher just out of college or a working professional planning a career switch, Quality Thought offers the best platform to become a skilled Full Stack Java Developer. With a focus on practical learning and job readiness, many of our students are now placed in top IT companies across India.

Join Quality Thought today – Get trained, get certified, gain real-world experience, and step confidently into the IT industry!

🔹 What is Dependency Injection (DI)?

Dependency Injection in Spring is a design pattern where the Spring container is responsible for creating objects (beans) and injecting their dependencies, instead of the class creating them itself.

This promotes loose coupling, reusability, and testability.

🔹 Without DI (Tight Coupling)


class Car {
    Engine engine = new Engine(); // Car creates its own Engine
}

Here, Car depends directly on Engine.
If we want a different type of engine (e.g., ElectricEngine), we must modify the Car class → tight coupling.

🔹 With DI (Loose Coupling using Spring)


class Engine {
    void start() {
        System.out.println("Engine started");
    }
}

class Car {
    private Engine engine;  // dependency

    // Dependency is injected via constructor
    public Car(Engine engine) {
        this.engine = engine;
    }

    void drive() {
        engine.start();
        System.out.println("Car is moving");
    }
}

🔹 How Spring Handles DI

Spring can inject dependencies in 3 ways:

Constructor Injection (recommended)


@Component
class Car {
    private final Engine engine;

    @Autowired
    public Car(Engine engine) {
        this.engine = engine;
    }
}

Setter Injection


@Component
class Car {
    private Engine engine;

    @Autowired
    public void setEngine(Engine engine) {
        this.engine = engine;
    }
}

Field Injection (not recommended for testing)


@Component
class Car {
    @Autowired
    private Engine engine;
}

🔹 Benefits of DI

Loose coupling between classes.
Easier unit testing (can mock dependencies).
Configuration flexibility (swap implementations without changing code).
Cleaner and maintainable code.

✅ In short:
Dependency Injection means giving an object its dependencies from the outside (Spring container), instead of the object creating them itself.

Search This Blog

Full stack java