Just I little question out of curiosity:
Do multiple As exist at the same time or is the lifetime of an A
strictly separated (time wise) from the other As.
If multiple As exist at the same time. How do you decide to which A a B
belongs while it is requesting injection of C...
On 21.10.2016 08:58, Tonni Tielens wrote:
Thanks for the answer. In the mean time we've managed to get this
working by indeed using a custom scope. In our situation the lifetime
of A is indeed very well understood and A is only created at one point
in the code (the entry point of our application). So we expect that
nobody would ever need to enter or leave the scope manually in other
points.
2016-10-20 17:47 GMT+02:00 Luke Sandberg <[email protected]
<mailto:[email protected]>>:
There are two common options
1. you could use assisted injection or @AutoFactory to create a
factory for the b's that allow you to pass an explicit object.
Then A can just construct a C and pass it to all of its Bs
2. you could introduce a custom scope managed by a1 and a2. This
is sometimes appropriate but can be a fair bit of work to
implement and manage
I generally recommend against custom scopes unless
1. the lifetime is very well understood and generally strictly
contained within another scope (for example, if you are using
RequestScope, your custom scopes probably shouldn't span requests
without a lot of care to prevent request data from 'leaking')
2. there are a small number (ideally 1) of ways to 'enter' the scope.
3. you have exhausted other options :) like assisted injection.
Also, in general, Guice doesn't need to control every part of your
application, so if the relationships between A B and C don't map
well to a guice concept you could always just handle that part of
your application 'manually' and let guice handle the rest.
On Thu, Oct 13, 2016 at 12:00 AM Tonni Tielens
<[email protected] <mailto:[email protected]>> wrote:
Hi all,
We're working on quite a big project, already using dependency
injection in 90% of the places, but without a framework. After
having to modify 33 files just to add one dependency into one
deeply nested class, I'm convinced that we should use a DI
framework. Google Guice is one of the candidates. I've read
the guide and learned about scopes, but one thing that is
unclear to me is the following.
What we have is something like this. Class A, that contains
one or more objects of type B, that each contain a reference
to the same object of type C. My question is about C. You
might think that C should be a singleton, but actually it's a
bit more complex. The scope of C depends on A. Hence, for each
A there should be one C. And all the B's in that A instance
should have a reference to that instance of C, while all the
B's in the other A's instance, should have a reference to the
other C instance.
So something like this:
a1 -> b1 -> c1
a1 -> b2 -> c1
a1 -> b3 -> c1
a2 -> b4 -> c2
a2 -> b5 -> c2
a2 -> b6 -> c2
Is this possible using Guice? How would one do this?
Regards,
Tonni Tielens
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