the standard java way to solve this is the service loader pattern.
java 6 has explicit support in the serviceloader class, but it is easy to
use classloader.getResources(...) note that's a plural, to roll your own if
you need to support java 5 or earlier.
basically the factory looks for files called
/META-INF/services/fullyqualifiedinterfaceclassname
those files contain the name(s) of implementations of the interface.
no circular dependency required.
a more modern solution is to use dependency injection so that the
implementations have eg @Producers. this is effectively the same as
serviceloader but can be more flexible
- Stephen
---
Sent from my Android phone, so random spelling mistakes, random nonsense
words and other nonsense are a direct result of using swype to type on the
screen
On 7 Jan 2012 04:24, oweijr oweirj stupid...@yahoo.com wrote:
I have a set of interfaces and then multiple
implementations of the interfaces. Only one implementation is used in a
given instance of the application.
I'm trying to create separate
projects for the common interface and each of the implementations.
However, the problem I have is that in order to implement the common
interface, each of the implementation projects needs to depend on the
common interface project. I also need to create a factory method somewhere
which will return the appropriate version of the implementation based on
some parameters. It seems logical to put this factory into the common
project. However, I cannot do this because the implementation projects
depend on the common one and this creates a circular dependency in maven.
How does one typically solve this sort of problem. I could create yet
another project which contains the factory and depends on all the other
projects. Is there a more sensible way?
parent +--- common-interface +--- implementation-1 - depends on
common-interface +--- implementation-2 - depends on common-interface
Where does the factory go? It depends on all 3 of the above.
TIA
