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If you are using spring (or any of the less cumbersome DI frameworks) this is exactly true. Generally in Java DI frameworks you make a bunch of factory methods

If you are using spring (or any of the less cumbersome DI frameworks) this is exactly true. Generally in Java DI frameworks you make a bunch of factory methods for your logic classes(this may be magically done through annotations). A singleton in this approach is just a factory that always returns the same object.

chubot 9y ago
What I don't really understand is why you need a DI framework in Java. I use this style Python all the time with zero frameworks. You just make the objects in main() and make the objects in your test main(). Use helper functions if necessary. I do think Spring was very influential because I remember other people in the mid-2000's talking about testing, dependency injection, and Spring. I recall lots of people using Guice at Google but I never used it since I did very little Java. I feel like there is something about Java where you need a DI framework, and in Python you don't. I don't feel like you need one in C++ either. Or it might not even be possible to write one. I think LLVM is written in C++ in a style with zero globals. It's a library-based design.
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- dom0 9y ago
  Python has had closures for a long time, which make great ad-hoc factories that can capture state from upstream functions without making state visible along the way.
  - chubot 9y ago
    Yeah that can probably help. Another thing that helps is keyword arguments, so you avoid the verbose builder pattern that's idiomatic in Java. I was going to say that I don't use closures in Python all that much, and Python has some issues with closures (e.g. nonlocal is ugly, and it wasn't even there until Python 3). But after watching a recent PyCon talk [1], I realized that the "bound method" feature of Python is a useful special case of a closure. And he makes the good point that the code is shorter than JavaScript which requires an explicit anonymous function or bind(). [1] https://us.pycon.org/2017/schedule/presentation/768/ https://us.pycon.org/2017/schedule/presentation/768/
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chubot 9y ago

What I don't really understand is why you need a DI framework in Java. I use this style Python all the time with zero frameworks. You just make the objects in main() and make the objects in your test main(). Use helper functions if necessary. I do think Spring was very influential because I remember other people in the mid-2000's talking about testing, dependency injection, and Spring. I recall lots of people using Guice at Google but I never used it since I did very little Java. I feel like there is something about Java where you need a DI framework, and in Python you don't. I don't feel like you need one in C++ either. Or it might not even be possible to write one. I think LLVM is written in C++ in a style with zero globals. It's a library-based design.

deleted 9y ago
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dom0 9y ago
Python has had closures for a long time, which make great ad-hoc factories that can capture state from upstream functions without making state visible along the way.
- chubot 9y ago
  Yeah that can probably help. Another thing that helps is keyword arguments, so you avoid the verbose builder pattern that's idiomatic in Java. I was going to say that I don't use closures in Python all that much, and Python has some issues with closures (e.g. nonlocal is ugly, and it wasn't even there until Python 3). But after watching a recent PyCon talk [1], I realized that the "bound method" feature of Python is a useful special case of a closure. And he makes the good point that the code is shorter than JavaScript which requires an explicit anonymous function or bind(). [1] https://us.pycon.org/2017/schedule/presentation/768/ https://us.pycon.org/2017/schedule/presentation/768/
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