+1 On Thu, Nov 10, 2011 at 3:44 PM, Vincent Massol <[email protected]> wrote:

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/Provi...

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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-- Thomas Mortagne

+1 Caleb On 11/10/2011 09:44 AM, Vincent Massol wrote:

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/Provi...

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

_______________________________________________ devs mailing list [email protected] http://lists.xwiki.org/mailman/listinfo/devs

+1 Best regards, Andreas Jonsson 2011-11-10 15:44, Vincent Massol skrev:

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/Provi...

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

_______________________________________________ devs mailing list [email protected] http://lists.xwiki.org/mailman/listinfo/devs