Design - Interview Questions and Answers for 'Inversion of control' | Search Interview Question

Design - Interview Questions and Answers for 'Inversion of control' - 7 question(s) found - Order By Newest

Almost sure to be asked in every company using any Dependency Injection framework ( Spring, Guice etc )

Q1. What is Dependency Injection or IOC ( Inversion of Control ) ?

Ans. It is a Design Pattern that facilitates loose coupling by sending the dependency information ( object references of dependent object ) while building the state of the object. Objects are designed in a manner where they receive instances of the objects from other pieces of code, instead of constructing them internally and hence provide better flexibility.

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Q2. What are the benefits of Dependency Injection or IOC ?

Design

Ans. Central place for configuring dependencies.

No need to create object, container manage all this By using Run time polymorphism and association.

Facilities development of framework / libraries by injecting implementation classes in the implementation code.

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Q3. What are the different ways in which dependency injection can be done using Spring Framework ?

Spring

Ans. Using Constructor and Setters.

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Q4. Difference between constructor and setter injection ?

Spring

Ans. 1. In Setter Injection, partial injection of dependencies can possible, means if we have 3 dependencies like int, string, long, then its not necessary to inject all values if we use setter injection. If you are not inject it will takes default values for those primitives1. In constructor injection, partial injection of dependencies cannot possible, because for calling constructor we must pass all the arguments right, if not so we may get error

2. Setter Injection will overrides the constructor injection value, provided if we write setter and constructor injection for the same property [i already told regarding this, hope you remember ] But, constructor injection cannot overrides the setter injected values

3. If we have more dependencies for example 15 to 20 are there in our bean class then, in this case setter injection is not recommended as we need to write almost 20 setters right, bean length will increase. In this case, Constructor injection is highly recommended, as we can inject all the dependencies with in 3 to 4 lines [i mean, by calling one constructor]

4. Setter injection makes bean class object as mutable [We can change ] .Constructor injection makes bean class object as immutable [We cannot change ]

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Q5. Which of the OOP's features facilitate dependency injection ?

Design

Ans. Inheritance , Runtime Polymorphism and Composition.

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Q6. Is dependency injection possible if we don't have inheritance / Composition ?

Design

Ans. Without composition - No, as it's the core of dependency injection.

With Inheritance - Yes, through interface implementation.

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Q7. What could be the driving force to have dependencies injected through class than through config file while using IOC or Dependency Injection ?

Design

Ans. Unit Testing

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