Static member question

[derekv <de...@yahoo.com>]

Lets say, i have a class in bundle "Main" that calls a method from a class
that is exported from "BundleA" and it calls the setConfiguration() method
of the javax.security.auth.login.Cofiguration. That method is static and
sets a static member. Now, lets say i have that same class in bundle "Main"
call a method from a class that is exported from "BundleB" and that method
also calls the setConfiguration() method. Will i have two instances of the
same singleton because the caller is in two different bundles? or will i
have one instance because they are both called from the bundle "Main"???

// Main bundle
class Main {
  public void someMethod() {
    servicea.methodA();
    serviceb.methodB();
  }
}

// BundleA
import javax.security.auth.login.*;
class Servicea {
  public void methodA() {
    Configuration.setConfiguration(a);
  }
}

// BundleB
import javax.security.auth.login.*;
class Serviceb {
  public void methodB() {
    Configuration.setConfiguration(b);
  }
}
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RE: Static member question

[Sergey Shcherbakov <ss...@echelon.de>]

Hello everybody,

Recently embedding Felix (Karaf) I ran into the exactly same issue:
http://www.mail-archive.com/dev@felix.apache.org/msg04908.html

While the solution with setting TCL to null works I was wondering
whether this solution remains recommended one?
The issue looks to be fixed also by setting log4j.ignoreTCL=true in the
system/config properties.

Best Regards,
Sergey Shcherbakov.

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Re: Static member question

[Rob Walker <ro...@ascert.com>]

Just to expand on Richard's explanation a little -

    * statics are global within the scope of their classloader

So as Richard says, in your case since the class was loaded by one 
classloader, you'll still have a singleton across your JVM

In a case where the same class appears in different bundles, and is 
loaded locally by that bundle's classloader (e.g. neither class is 
resolved to the other by imports/exports) then any statics in that class 
will not be singletons in terms of the whole JVM - they'll only have 
singleton scope for their bundle.

-- Rob

Richard S. Hall wrote:
> There is only one singleton because there is only one copy of the 
> Configuration class in BundleA...assuming both Main and BundleB both 
> import javax.security.auth.login (i.e., they don't have a private copy 
> in their bundle) and they are both wired to the same provider of the 
> package.
>
> -> richard
>
> On 5/8/09 1:42 PM, derekv wrote:
>> Lets say, i have a class in bundle "Main" that calls a method from a 
>> class
>> that is exported from "BundleA" and it calls the setConfiguration() 
>> method
>> of the javax.security.auth.login.Cofiguration. That method is static and
>> sets a static member. Now, lets say i have that same class in bundle 
>> "Main"
>> call a method from a class that is exported from "BundleB" and that 
>> method
>> also calls the setConfiguration() method. Will i have two instances 
>> of the
>> same singleton because the caller is in two different bundles? or will i
>> have one instance because they are both called from the bundle "Main"???
>>
>> // Main bundle
>> class Main {
>>    public void someMethod() {
>>      servicea.methodA();
>>      serviceb.methodB();
>>    }
>> }
>>
>> // BundleA
>> import javax.security.auth.login.*;
>> class Servicea {
>>    public void methodA() {
>>      Configuration.setConfiguration(a);
>>    }
>> }
>>
>> // BundleB
>> import javax.security.auth.login.*;
>> class Serviceb {
>>    public void methodB() {
>>      Configuration.setConfiguration(b);
>>    }
>> }
>>    
>
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> To unsubscribe, e-mail: users-unsubscribe@felix.apache.org
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-- 


Ascert - Taking systems to the Edge
robw@ascert.com
+44 (0)20 7488 3470
www.ascert.com

Re: Static member question

["Richard S. Hall" <he...@ungoverned.org>]

There is only one singleton because there is only one copy of the 
Configuration class in BundleA...assuming both Main and BundleB both 
import javax.security.auth.login (i.e., they don't have a private copy 
in their bundle) and they are both wired to the same provider of the 
package.

-> richard

On 5/8/09 1:42 PM, derekv wrote:
> Lets say, i have a class in bundle "Main" that calls a method from a class
> that is exported from "BundleA" and it calls the setConfiguration() method
> of the javax.security.auth.login.Cofiguration. That method is static and
> sets a static member. Now, lets say i have that same class in bundle "Main"
> call a method from a class that is exported from "BundleB" and that method
> also calls the setConfiguration() method. Will i have two instances of the
> same singleton because the caller is in two different bundles? or will i
> have one instance because they are both called from the bundle "Main"???
>
> // Main bundle
> class Main {
>    public void someMethod() {
>      servicea.methodA();
>      serviceb.methodB();
>    }
> }
>
> // BundleA
> import javax.security.auth.login.*;
> class Servicea {
>    public void methodA() {
>      Configuration.setConfiguration(a);
>    }
> }
>
> // BundleB
> import javax.security.auth.login.*;
> class Serviceb {
>    public void methodB() {
>      Configuration.setConfiguration(b);
>    }
> }
>    

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