[rules-users] Null pointer exception when using global in rdrl 6.0.1.F

[Wolfgang Laun]

On 28/01/2014, SrjTx <clickthex at yahoo.com> wrote:
> I have a class that I declared final, has a private constructor, has only
> static members and methods.
> Some of its members are static instance of classes.
> In KIE-WBI added a global of that type with name X

You can't use a global that has a type X as you describe it, as you won't
be able to instantiate an X object if the constructor is private. (OK, you
could have a static getInstance method according to the singleton
pattern - but the use of an object where everything in the class
is static is rather doubtful.)

>
> When I try to make a call on X.foo(), I get a null pointer exception.

Well, if there's no object you haven't initialised the global.

> (note
> that x.foo() calls y.foo(), where y is a static member of X.
>
> I've read some posts that a global has to be static, am I stretching, what
> it means for a global to be static?

I don't know where you've read that, but do read the documentation first.

>
> I am guessing I need to write some java code that will create an instance
> of
> X and inject into working memory?

You are guessing, and you are guessing wrong.

  kSession.setGlobal( "theDRLnameOfTheGlobal", new XbutNotAsYouDescribedIt() )

>  I was hoping to be able to create this
> object within either the drools or SY framework.
>
> I have googled and be reading on this for quite a bit now, but I think I
> have succeeded only in confusing myself.
>
> Any help greatly appreciated.

Documentation, 7.5.2, global - about all you need to know.

-W

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