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Re: [equinox-dev] [OSGi] practices with the bundle context

Hi
 
>> "storing it will do no good"
The BundleContext object of a bundle is valid only when the bundle is in STARTING, ACTIVE and STOPPING state
In all other states all its methods should cease to work (i.e. throw IllegalStateException).
So storing it is reasonable as long as the bundle is in one of the listed states.
 
Example:
 
1. start the bundle
state is STARTING for some time bundle context is valid
bundle state becomes ACTIVE 
BundleContext object is valid here
....
BundleContext object is still valid here  :-)
2. stop  the bundle - state is STOPPING for some time - BundleContext is still valid here.
bundle state becomes RESOLVED or INSTALLED - BundleContext object is NOT valid here
 
using the BundleContext after this point is not correct and should not be done (it will do no good too).
 
If the bundle is started again then a new BundleContext object will be created and it should be used
 
>> "you usually [make the context accessible to other objects]"
Yes, but to objects inside the bundle to which the BundleContext belongs. Passing this object outside the
bundle is a bad practice however should not do any harm to the framework.
 
Best regards
Vasil
----- Original Message -----
Sent: Wednesday, July 09, 2003 3:41 PM
Subject: Re: [equinox-dev] [OSGi] practices with the bundle context


It seems to me that there is something contradictory in what you said:
        "storing it will do no good"
        "you usually [make the context accessible to other objects]"

There is only two times you can get the context (start / stop), so how do you make it available
to other part of your bundle, if you do not store it?

Does the spec specify something about the life time of the object?

        PaScaL



Benjamin Reed/Almaden/IBM@IBMUS

07/08/2003 07:30 PM

       
        To:        Pascal Rapicault/Ottawa/IBM@IBMCA
        cc:        equinox-dev@xxxxxxxxxxx
        Subject:        Re: [equinox-dev] [OSGi] practices with the bundle context



> What are the regular practice with the bundleContext?
>     Do you store it?

No, it is a transient object, so storing it will do no good.

>     Do you make it accessible to other classes in the bundle?

Yes, usually you do. It is important though not to let a BundleContext
leak out to other bundles. The BundleContext is a bundle's interface to
the framework, so a bundle can masquerade as another bundle if it has
that bundle's BundleContext.

>     Do you surface some of its API in the activator and store the
> activator somewhere?

I wouldn't surface the API in the activator, but certainly you may
surface some of the functionality in other objects. Often though you
just end up passing around the BundleContext.

> Basically it offers a lot of functions that are interesting to install
> bundles, and get information about the platform.
> So how am I supposed to proceed for other classes of my bundle to use
> those facility?

Except for instances where the BundleContext may leak to other bundles,
I wouldn't feel bad about passing around the BundleContext.

ben