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springdependency-injectioninversion-of-controlioc-container
CuriousMind
CuriousMind

Reputation: 8943

Ioc Container: Dependency Injection, Dependency Lookup?

I am trying to understand Spring Framework more what I know currently, and I am referring to "Pro Spring 3" book.

I came across the following section in the book as below:

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It says that in general IoC can be decomposed into two components viz: Dependency Injection and Dependency Lookup.

With respect to this, I have following questions:

1) Do Spring provide both Dependency Injection ,Dependency Lookup ?

2) Do all Ioc container have both these systems viz: Dependency Injection ,Dependency Lookup?

3) If Spring provides both Dependency Injection ,Dependency Lookup, then isn't it wrong to say that Spring is DI framework, when it has both these capabilities?

Upvotes: 1

Views: 843

Answers (1)

Jesper
Jesper

Reputation: 206996

1: Yes, Spring provides both dependency injection and dependency lookup. You can let Spring inject dependencies using for example the @Autowired annotation, and you can also manually lookup components from Spring's ApplicationContext by calling one of the getBean methods.

The main thing to understand about the concept "inversion of control" (IoC) is that Spring does the work for you, instead of the other way around: you let Spring create instances of your components, and you let Spring inject the dependencies, instead of the other way around, where you write code yourself to create instances and lookup dependencies.

2: No, not necessarily.

3: Spring can do dependency injection (DI), so it is a DI framework. Just because it also does other things (such allow you to lookup components explicitly) doesn't suddenly not make it a DI framework anymore.

Upvotes: 2

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