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Eclipse4 DI reinject? [message #966885]

Thu, 01 November 2012 06:07

Christian Eugster
Messages: 124
Registered: July 2009
Location: St. Gallen Switzerland

Senior Member

Hi,

I have read, that the Eclipse4 DI framework does reinject a service if it has changed. Does it do this in a "silent way" or what opportunity has the "client" to react on this change?

E.g. I use a service to get instances from a database. If that service stops running, I want to remove the instances from the ui. How can I accomplish this?

Thanks!

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Re: Eclipse4 DI reinject? [message #966914 is a reply to message #966885]

Thu, 01 November 2012 06:34

Thomas Schindl
Messages: 4462
Registered: July 2009

Senior Member

If you use method injection your method gets called and you can react on
that.

Tom

Am 01.11.12 11:07, schrieb Christian Eugster:
> Hi,
> I have read, that the Eclipse4 DI framework does reinject a service if
> it has changed. Does it do this in a "silent way" or what opportunity
> has the "client" to react on this change?
> E.g. I use a service to get instances from a database. If that service
> stops running, I want to remove the instances from the ui. How can I
> accomplish this?
>
> Thanks!

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Re: Eclipse4 DI reinject? [message #966919 is a reply to message #966885]

Thu, 01 November 2012 06:40

Sopot Cela
Messages: 448
Registered: December 2010

Senior Member

suppose you have

@Inject
public void doStuff(IMyService service){blablabla}

There are two alternatives:
1. you get IMyService through a context function
2. you get it directly from an IEclipseContext

1: If any value in the context which is used to compute the IMyService runtime class changes then the IMyService is reinjected and the method is re-called with the new value

2: If you change it through something like

eclipseContext.set(IMyService.class, myNewServiceObject)

the method is also re-called with the new value.

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Re: Eclipse4 DI reinject? [message #966971 is a reply to message #966919]

Thu, 01 November 2012 07:35

Christian Eugster
Messages: 124
Registered: July 2009
Location: St. Gallen Switzerland

Senior Member

Hi!

That's cool: and when I add @Optional the method is called when the service stops too!

Thank you both!

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Re: Eclipse4 DI reinject? [message #966976 is a reply to message #966971]

Thu, 01 November 2012 07:37

Sopot Cela
Messages: 448
Registered: December 2010

Senior Member

@Optional prevents it from being called when it becomes null.

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Re: Eclipse4 DI reinject? [message #967002 is a reply to message #966976]

Thu, 01 November 2012 08:05

Christian Eugster
Messages: 124
Registered: July 2009
Location: St. Gallen Switzerland

Senior Member

So do I misunderstand something? I thought that @Optional does not prevent the method call, but does not throw an exception. When I want to be noticed about a service stops, how do I implement this then?

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Re: Eclipse4 DI reinject? [message #967003 is a reply to message #967002]

Thu, 01 November 2012 08:07

Sopot Cela
Messages: 448
Registered: December 2010

Senior Member

It depends what you mean by "service stops" do you have a mechanism to null the service in the context when something happens? The framework can not "automatically" check and act when a service "stops" as it is a bit ambiguous what you call stop.

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Re: Eclipse4 DI reinject? [message #967024 is a reply to message #966976]

Thu, 01 November 2012 08:26

Christoph Keimel
Messages: 277
Registered: December 2010
Location: Germany

Senior Member

@Sopot: I think you've got a criss-cross in your post Wink

: @Optional allows (not prevents) the value to be injected with null

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Re: Eclipse4 DI reinject? [message #967036 is a reply to message #967003]

Thu, 01 November 2012 08:38

Christian Eugster
Messages: 124
Registered: July 2009
Location: St. Gallen Switzerland

Senior Member

I have an OSGi Service that provides DAOs. When dependencies are no longer fulfilled, the service is deactivated and so not anymore reachable.

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Re: Eclipse4 DI reinject? [message #967332 is a reply to message #967036]

Thu, 01 November 2012 13:35

Lars Vogel
Messages: 1043
Registered: July 2009

Senior Member

Of course if the OSGi services is stopped than the field or method injection will be performed again if you use @Optional. Have a look at the Javadoc of @Optional it depends where you use it.

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Re: Eclipse4 DI reinject? [message #968235 is a reply to message #967024]

Fri, 02 November 2012 05:57

Sopot Cela
Messages: 448
Registered: December 2010

Senior Member

Christoph Keimel wrote on Thu, 01 November 2012 13:26

@Sopot: I think you've got a criss-cross in your post : @Optional allows (not prevents) the value to be injected with null

true.

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