assign null in constructor param

[joe panico-2]

Hello,

My setup is PicoContainer 2.8.3 against JVM 1.5.

I'm trying to explicitly assign a null in a constructor param:

===
public class ComponentClass{
    public ComponentClass(ArgClass arg)
    }
}

pico.addComponent("myComponent", ComponentClass.class, new
ConstantParameter(null))
===

produces an unsatisfied dependency error on ArgClass. That's the exact
same result as this:

===
pico.addComponent("myComponent", ComponentClass.class, new ComponentParameter())
===

which makes me think that both calls are going down the same auto
wiring path. How can I get a null assigned?

thanks,

Joe

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[Michael Rimov]

> My setup is PicoContainer 2.8.3 against JVM 1.5.
>
> I'm trying to explicitly assign a null in a constructor param:
>
> ===
> public class ComponentClass{
>     public ComponentClass(ArgClass arg)
>     }
> }
>
> pico.addComponent("myComponent", ComponentClass.class, new
> ConstantParameter(null))
> ===
>
> produces an unsatisfied dependency error on ArgClass. That's the exact
> same result as this:
>
> ===
> pico.addComponent("myComponent", ComponentClass.class, new
> ComponentParameter())
> ===
>
> which makes me think that both calls are going down the same auto
> wiring path. How can I get a null assigned?

Joe,

I took a look and Pico definitely cannot do it with your code base.  (The
ConstantParameter has some type checking which returns false if the parameter is
null.)

I took a stab with a new Parameter class to specifically handle Nulls, but
SingleMemberInjector is currently guarded against null parameters.... if I
change that particular behavior without the checking with the other developers,
I'd be causing problems.  Sorry.

I've opened issue PICO-364 here: http://jira.codehaus.org/browse/PICO-364

The workaround until we get this fixed is:

        pico.addComponent("myComponent",
                new ComponentClass(
                        pico.getComponent('arg1'),
                        pico.getComponent('arg2'),
                        null)
                );

(That's the beauty of using Scripts and Java for Application composition, you
can always do individual objects manually if all else fails.)

Thanks for reporting this, and I hope the workaround helps.

                                                                        -Mike




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