Hi devs,
I've started investigating this. The documentation for Provider can be found
here:
http://code.google.com/p/atinject/source/browse/trunk/src/javax/inject/Provider.java
Here's we would define a provider:
@Component
public class MyProvider implements Provider<RoleToProvide>
{
@Inject <-- just to show that a provider is a component and be injected
other components
private SomeRole role;
@Override
public RoleToProvide get()
{
… logic here to return a RoleToProvide instance…
}
}
And here's how you'd use it:
@Component
public class MyComponent implements MyRole
{
…
@Inject
private Provider<RoleToProvide> provider;
…
public void someMethod()
{
RoleToProvide instance = this.provider.get();
…
Rationale:
=========
* UC1: Useful to break cyclic dependencies in a cleaner way than having the
ComponentManager injected, especially since the Provider can be reused since
it's shared
* UC2: Useful to clean up code so that the logic to decide which implementation
to return can be externalized in a Provider implementation. For example imagine
you have a config property in xwiki.properties and based on it you wish to
return a component with one hint or another. You could use a Provider for this.
* Allows us to be JSR330 compliant (not a very strong point but still an
argument ;))
Default Provider
=============
When you ask to get injected a Provider if no Provider is defined for the Role
you wish, you'll get injected a generic provider which simply does a lookup
using the Component Manager. This allows to simply implement UC1.
WDYT?
Thanks
-Vincent
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