Why interface is created

Question

i am new to spring

in my spring web project DAO and service they created the interface and implementing it created class. can we liminate interface.

Interface gives you flexibility, in case in future you want to pass it with some different implementaion. — Gaurav Gupta, Jan 29 '20 at 09:15
@Sangam.R, It's a design pattern. Please check about the design pattern https://www.tutorialspoint.com/design_pattern/data_access_object_pattern.htm — Srini, Jan 29 '20 at 09:21
https://stackoverflow.com/questions/256255/spring-and-interfaces — R.G, Jan 29 '20 at 09:26
A better explanation to it can be found [here](https://stackoverflow.com/questions/256255/spring-and-interfaces). — Himanshu Jain, Jan 29 '20 at 10:24
It seems that you need to go through Java Core and design patterns first because it seems you still cannot understand why interfaces are required overall in Java. — zawarudo, Jan 29 '20 at 12:35

score 0 · Answer 1 · answered Jan 29 '20 at 11:19

The whole point of using interface is to create abstraction. When you call you DAO from Service, your service is not aware of the actual implementation of DAO/ cases in which you have multiple implementations of your DAO interface, your service is not aware of the actual impl being used.

With spring you will use - Autowire to inject the dependency. You will refer your Dependency using interface.

    @Component/@Service
    class ServiceImpl {
      @Autowired
      private DAOInterface dao;

      // Rest of code
    }

Spring knows - to create the instance of this ServiceImpl it needs to inject a concrete impl of DAOInterface type. In case you have concrete implementation, it does so. In case you have multiple impls - you need to define by bean name which implementation you need using @Qualifier.

Interface is kind of a contract for your impl classes. Other than abstracting the actual impl, it helps you decoupling the layers by not directly having a dependency on the concrete classes. This is a good design pattern

Why interface is created

1 Answers1