Have a look at
https://github.com/google/guice/wiki/Multibindings
this does not solve the problem of how to configure them. But it
allows you to inject a set/map of things.
On 11/07/2016 11:42 PM, Dominik wrote:
I want to inject a sequence of components where
each component implements the same interface. Each of the
components may have dependencies themselves which may vary
amongst the different implementations of the interface. The
actual sequence shall be configurable by the user by means of a
configuration file or any mechanism that is made available
through the dependency injection framework (guice).
To be more concrete I'll give an example:
interface Machine {...}
class Dishwasher implements Machine {
// Here some dependencies
should be injected.
}
class VacuumCleaner implements Machine {
//
Here some dependencies should be injected.
class Household {
// Here I want to inject a
sequence of `Machine`s.
}
// Now the user may specify
in whatever way which machines are present in the
household,
// and this setting is not
changing during runtime.
// For example (using an arbitrary notation):
//
//
//
//
//
//
//
//
//
//
//
//
//
//
//
//
//
//
//
// So the household would have three `Machine`s, two
of which are `VacuumCleaner`s
// (where each `VacuumCleaner` itself depends on a
different implementation of another interface)
// and one `Dishwasher`.
How can I realize this using guice? I could write a custom
provider for the `Machine`s (i.e. a `MachineFactory`), however
the pattern that "a component depends on a sequence of others
with dependencies themselves" may repeat further down the chain,
so I would be forced to write providers/factories for all of
them. This somehow breaks the purpose of dependency injection
where I can request a component and all dependencies are
resolved automatically by the framework. Furthermore it requires
the factory to have knowledge about the possible dependencies of
all implementations of the interface which breaks the separation
of dependencies from the application: whenever I add a new
implementation (a new Machine, e.g. `WashingMaschine`) I need to
check whether the factory already requests all required
dependencies for the `WashingMaschine` in order to "inject" them
manually into the `WashingMaschine` later on. If a new
dependency is introduced I need to fix the factory accordingly.
Any ideas? Thanks! Cheers, Dominik
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