For what it's worth, this is exactly how I structure our code base: most of
our types are either directly injected or they define an assisted factory:
class A {
public interface IFactory {
A create(String param);
}
@Inject
private A(@Assisted String param, Dependency1 dep1, Dependency2 dep2) {
// ...
}
}
I don't see anything wrong with this pattern (I did mention a weakness when
it comes to inheritance on this list last week, look into the archives for
the discussion, but there is no clear answer to that one).
--
Cédric
--
Cédric
On Wed, Feb 20, 2013 at 7:10 AM, Bram <[email protected]> wrote:
> I'm experiencing some problems with implementing Guice / DI in the proper
> way. I end up creating allot of a factories because I need objects with
> specific settings that I only know at runtime. As an example, imaging the
> following:
>
> A connection object that can send/receive "something" and connects to a
> host:port:
>
> public Connection(String host, int port);
>
> A http client that needs a connection:
>
> public HttpClient(Connection connection);
>
>
> Now, when I need a HttpClient in one of my objects (for example, a
> crawler) I can't magically get that injected with the correct settings
> (host/port). What I end up doing is creating factories for both the
> Connection and the HttpClient:
>
> public interface ConnectionFactory {
> public Connection create(String host, int port);
> }
>
> public interface HttpClientFactory {
> public HttpClient create(Connection connection);
> }
>
> And my constructors then look like this:
>
> public Connection(@Assisted String host, @Assisted int port);
> public HttpClient(@Assisted Connection connection);
>
> And I have to inject both factories in, for example, my webcrawler to be
> able to get a HttpClient:
>
> class WebCrawler {
> private final HttpClientFactory httpClientFactory;
> private final ConnectionFactory connectionFactory;
>
> @Inject
> public WebCrawler(HttpClientFactory httpClientFactory,
> ConnectionFactory connFactory) {}
>
> public void someMethod() {
> Connection conn = connectionFactory.create(host, port);
> HttpClient client = httpClientFactory.create(conn);
> ....
> }
> }
>
> With this, everything is injectable and "loosly" coupled, but I have the
> feeling I'm missing the point somewhat. Instead of doing Connection = new
> Connection(..) i changed everything to xxFactory.create(..) and I have
> allot of factories injected in my classes. A second approach would be to
> inject the connection factory into the HttpClient but that also smells as
> "not the way to do it".
>
> What am I not seeing?
>
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