Spring Dependency Injection: Understanding the Basics

A popular Java-based framework for creating enterprise-level applications is Spring Framework. Dependency injection (DI), a design technique that enables you to manage your application’s dependencies, is one of the main components of the Spring Framework.

A technique called dependency injection is used to get rid of the hard-coded dependencies between several classes in an application. By allowing one component to depend on another’s interface rather than its actual implementation, you can construct loosely connected components. In other words, DI makes it possible for you to program to an interface rather than an implementation.

Spring Framework supports three types of Dependency Injection:

1. Constructor-based Dependency Injection:

In this type of injection, dependencies are injected through the constructor of the class.

In constructor injection, dependencies are passed as parameters to the constructor of the class. The advantages of constructor injection are:

public class Car {
    private Engine engine;
 
 public Car(Engine engine) {
        this.engine = engine;
    }
    public void start() {
        engine.start();
    }
}

Advantages:

1. The dependencies are made sure to be accessible at object creation, aiding in the creation of immutable objects.
2. Constructor injection helps in creating objects with all of their dependencies already set up.
3. It makes it simpler to quickly identify a class’s dependencies, which can aid in debugging.

Disadvantages:

1. Long constructors in classes with a lot of dependencies can be challenging to read and maintain.
2. Constructor injection can make it harder to create objects that have optional dependencies.
3. It may be more difficult to construct objects with optional dependencies when optional dependencies injection is used.

2. Setter-based Dependency Injection:

Dependencies are injected using this type of injection through the class’ setter methods.

public class Car {
    private Engine engine;

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

Advantages:

1. Setter injection permits optional dependencies, which may be advantageous in some circumstances.
2. Without altering the class’s constructor, dependencies can be added or removed more quickly and easily with setter injection.
3. When only a few dependencies are required, setter injection can be used for partial dependency injection.

Disadvantages:

1. It may be more difficult to understand and troubleshoot a class if its dependencies are not immediately apparent.
2. It may be more difficult to create immutable objects since the dependencies might not be available when the object is initially created.
3. It may be simpler to construct objects with erroneous or inconsistent dependencies when setter injection is used.

3. Field-based Dependency Injection:

In this type of injection, dependencies are injected through the class fields using Java Reflection.

@Component
public class FieldBasedInjection {

    @Autowired
    private MessageService messageService;

    public void processMsg(String message) {
        messageService.sendMsg(message);
    }
}

In field injection, dependencies are injected directly into the class fields using Java Reflection. The advantages of field injection are:

Advantages:

1. Field injection is simple to utilize since it does not require any new methods or constructors.
2. Field injection can facilitate the creation of objects with optional dependencies.
3. Field injection may be used for partial dependency injection, which requires only a few dependencies.

Disadvantages:

1. It may be more difficult to comprehend and debug classes since it may be more difficult to quickly identify a class’s dependents.
2. It may be more difficult to build objects with all of their dependencies in place when using field injection, which may make it more challenging to test the code.
3. Immutable object creation may become more challenging due to field injection.

Conclusion:
With the help of the potent technique known as dependency injection, you can build loosely linked components for your application. It is simple to handle the dependencies of your application with Spring Framework’s support for various methods of dependency injection. Utilizing DI, you can build applications that are more scalable and robust while also being simple to test, maintain, and extend.

Follow for more such content on spring and microservice.

Visit https://springworld.xyz/ for more such content

🚀 5 Proven Tactics to Optimize Performance and Boost Speed! 💨

👨‍💻🚀 Understanding the Spring Bean Life Cycle: A Crucial Concept for Every Spring Framework…

🔥 Boost Your Spring Boot App Performance with Caching: A Comprehensive Guide to Spring Boot…