Dependency Injection (DI) is a software design pattern that allows a class to receive its dependencies from an external source rather than creating them itself. This approach promotes separation of concerns, making the application easier to manage, extend, and test, while reducing boilerplate code. DI can be implemented using various methods, including constructor injection, setter injection, and interface-based injection.

2. What is Dependency Injection?
Inversion of Control
Types of Dependency Injection
Benefits of Dependency Injection
Implement Dependency Injection Using Spring Boot
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4. Class ClassA uses methods of B
Class A is Dependent on B
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5. Class ClassBefore A uses methods of B
Class A needs to create an instance of class B
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6. The process of creating an object for some other class and let the class directly using the
dependency is called dependency injection.
What is Dependency Injection(DI)?
Class DI
I need two objects
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7. The process of creating an object for some other class and let the class directly using the
dependency is called dependency injection.
What is Dependency Injection(DI)?
Class
DI
Create Objects
A objectA = new A()
B objectB = new B()
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8. The process of creating an object for some other class and let the class directly using the
dependency is called dependency injection.
What is Dependency Injection(DI)?
Class DI
Returns objects to the class
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9. Dependency Injection uses three types of classes. The injector class creates an object of
the service class. Then, the injector class injects the object to a client object.
What is Dependency Injection(DI)?
Client
Class
Injector
Class
Service
Class
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11. Concept Behind Dependency Injection
A class should not configure its dependencies statically but should be
configured by some other class from outside.
A class should concentrate on fulfilling its responsibilities like the flow of an
application, and not on creating objects
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13. Dependencies are
provided through a
class constructor
Injector method injects
the dependency to the
setter method exposed
by the client.
Injector uses Interface
to provide the
dependency to the client
class.
Constructor Setter Interface
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15. Email Service
Class
Objects
1. To email address
2. From email address
3. Subject
4. Body
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16. Email Service
Class Recreate the Class
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17. Using Dependency Injection
Change Objects at run time
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18. Reduction of
Boiler plate
code
Unit Testing is
made much
easier
Application can
be easily
extended
Enables an easy way
to interconnect the
components
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