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Simple question on using "Job" inside Eclipse [message #779613]

Mon, 16 January 2012 02:00

Eclipse User

Hi all-

I got a simple question on the "Job" concept in the eclipse plugin platform:
how could I know is a Job is executed in a new thread or in
the current thread?

For example:

new ReportingJob().schedule(); //I simply call schedule();

private class ReportingJob extends Job {
protected IStatus run(IProgressMonitor monitor) {
// ... omitted
return Status.OK_STATUS;
}
}

So, is the above ReportingJob() instance running in a new thread or not?

I found the Worker/Job scheduling mechanism inside eclipse is quite
complex, sometimes, a Job is executed in a new thread, while sometimes not.
it would be great if someone can kindly point me to some reference or tutorials.

thanks very much. Any comments are welcome

-Sai

Re: Simple question on using "Job" inside Eclipse [message #780135 is a reply to message #779613]

Tue, 17 January 2012 03:52

Eclipse User

On 1/16/2012 12:30 PM, Sai Mising name wrote:
> So, is the above ReportingJob() instance running in a new thread or not?
Same thread.

From javadoc of org.eclipse.core.runtime.jobs.Job.run(IProgressMonitor)
"Jobs can optionally finish their execution asynchronously (in another
thread) by returning a result status of ASYNC_FINISH. Jobs that finish
asynchronously must specify the execution thread by calling setThread,
and must indicate when they are finished by calling the method done."

> I found the Worker/Job scheduling mechanism inside eclipse is quite
> complex, sometimes, a Job is executed in a new thread, while sometimes not.
> it would be great if someone can kindly point me to some reference or
> tutorials.

You can go through this Eclipse Corner Article:
http://www.eclipse.org/articles/Article-Concurrency/jobs-api.html

--
Deepak Azad
http://wiki.eclipse.org/JDT/FAQ

Re: Simple question on using "Job" inside Eclipse [message #780429 is a reply to message #780135]

Tue, 17 January 2012 14:53

Eclipse User

Hi Deepak:

Thanks very much for your reply.

The information you provided is *very* useful.

As far as I understand, the purpose of "Job" is to make the UI responsive and active. Thus, all Jobs should be run in a separate and background thread instead of the current thread. Is that right? (probably the only exception is the UIJob, which explicitly desigates some operations to be run on the event dispatch thread).

So, for a non UI-Job like:

new ReportingJob().schedule(); //it will be executed in a separate thread? right?

private class ReportingJob extends Job {
protected IStatus run(IProgressMonitor monitor) {
//if I want to access UI object here,
//I must wrap it using asyncExec / syncExec to avoid invalid thread access
//right?
return Status.OK_STATUS;
}
}

If I understood something wrong, please point me out! Thank you!

-Sai

Re: Simple question on using &quot;Job&quot; inside Eclipse [message #780456 is a reply to message #780429]

Tue, 17 January 2012 23:12

Eclipse User

> As far as I understand, the purpose of "Job" is to make the UI
> responsive and active. Thus, all Jobs should be run in a separate and
> background thread instead of the current thread. Is that right?
What was I thinking? :-)
Of course a Job will run in a separate thread. It can be instructive to
have a look at org.eclipse.core.runtime.jobs.IJobManager and its
implementation org.eclipse.core.internal.jobs.JobManager.

> //if I want to access UI object here,
> //I must wrap it using asyncExec / syncExec to avoid invalid thread access
> //right?
Yes, or you can simply use UIJob if you want to do this.

--
Deepak Azad
http://wiki.eclipse.org/JDT/FAQ

Re: Simple question on using &quot;Job&quot; inside Eclipse [message #780684 is a reply to message #780456]

Wed, 18 January 2012 22:24

Eclipse User

Hi Deepak-

Thanks for your answer! Really appreciate your help.

A closely-related question, I also see JDT (and other eclipse components) uses
the class "Action" extensively. Usually, programmers override the

"public void run() "

method to do something. However, I found I still got invalid thread access errors
sometimes when accessing GUI object inside "run()", while sometimes not.

So, I am really wondering are all Action#run must be executed in UI-thread or non-UI thread? or it really depends? If so, could anyone kindly points me to some resources about code in Action is executed?

Thanks a lot

-Sai

Deepak Azad wrote on Tue, 17 January 2012 23:12

> As far as I understand, the purpose of "Job" is to make the UI
> responsive and active. Thus, all Jobs should be run in a separate and
> background thread instead of the current thread. Is that right?
Of course a Job will run in a separate thread. It can be instructive to
have a look at org.eclipse.core.runtime.jobs.IJobManager and its
implementation org.eclipse.core.internal.jobs.JobManager.

> //if I want to access UI object here,
> //I must wrap it using asyncExec / syncExec to avoid invalid thread access
> //right?
Yes, or you can simply use UIJob if you want to do this.

--
Deepak Azad
http://wiki.eclipse.org/JDT/FAQ

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