Spring @Autowire on Properties vs Constructor

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Yes, option B (which is called constructor injection) is actually recommended over field injection, and has several advantages:

  • the dependencies are clearly identified. There is no way to forget one when testing, or instantiating the object in any other circumstance (like creating the bean instance explicitly in a config class)
  • the dependencies can be final, which helps with robustness and thread-safety
  • you don’t need reflection to set the dependencies. InjectMocks is still usable, but not necessary. You can just create mocks by yourself and inject them by simply calling the constructor

See this blog post for a more detailed article, by one of the Spring contributors, Olivier Gierke.

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