On 25 Nov 2013, at 5:51, Brian Pontarelli wrote:
Constructor injection uses a language construct and is testable in
many different forms (mocked, injected, null, etc.). Private field
injection is using a backdoor in an API. Constructor injection also
provides documentation and a contract.
If you are arguing "constructor injection is better for these reasons"
that is fine - you find those reasons to be more of a value traded-off
for the value of brevity, etc. I don't think it's nearly so certain a
win, but I've not met many developers who aren't "absolutely certain"
that their choice between field and constructor injection is "the right
way". So take from that what you will. Personally, I find constructor
injection to be a slight win, where you can do it.
Additionally, the JVM makes guarantees about language constructs like
constructors. It does not do this for libraries, even those with JSR
interfaces like Guice. Although, Guice is solid and we all trust it,
field injection does not have the same guarantees from the JVM as
constructors.
And again, I don't think field injection advocates are saying those are
all illusory, I think they're saying that in their "lived experience"
(so to speak) they simply don't find these advantages to actually catch
very many bugs, prevent very many bugs, nor communicate intent any more
intentionally or clearly than the other signals with field injection.
In short, they can all agree with this statement and still not care.
Because it is a trade-off between advantages, and those comparisons and
valuations are subjective.
Christian.
Christian Gruber :: Google, Inc. :: Java Core Libraries :: Dependency
Injection
email: [email protected] :::: mobile: +1 (646) 807-9839
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