<div dir="ltr">Hi Christian,<br><div><br></div><div>These are both great questions, so no worries!<br></div><div><br><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex" class="gmail_quote">
* If I want to use a global "Context" in my complete "KNIME
Application", why is there the possibility to create several
contexts?<br></blockquote><div><br></div><div>Curtis can expand on this if necessary, but by avoiding one static Context, we allow multiple instances of applications to run in the same JVM with differing sets of Services, Plugins, and any other state that could be desired. I don't have specific use cases off hand, but fundamentally, avoiding static classes and allowing state to be encapsulated with each instance of a Context is considerably more flexible. I think the only advantage a static Context would have is that it might mitigate some confusion. ;)<br>
<br></div><div>Also, if you know you want a static Context, it's easy enough to create a static utility class with a getContext() method that provides a consistent Context instance for everything in your application.<br>
</div><br><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex" class="gmail_quote">
* How can I use the class "Scifio" in a global way, s.t. this
context also knows all other services? The "Scifio" Context class
itself suggests to create one context for ImageJ2, one for SCIFIO,
etc.?!<br></blockquote><br></div><div>I'm not sure exactly what you mean when you reference the "Scifio" Context. But note that <a href="https://github.com/scifio/scifio/blob/master/scifio/src/main/java/io/scif/SCIFIO.java#L97">the SCIFIO class</a> has a constructor that accepts an existing Context. The SCIFIO class was designed, fundamentally, to act as a wrapper for existing Contexts. So you can maintain your one application context, and create a new SCIFIO around it when needed. The zero-param constructor is primarily a convenience for when you don't have/need a Context already in your application.<br>
<br></div><div>So to make SCIFIO global, just have a single global Context and then wrap it with a SCIFIO whenever you need the SCIFIO API. There are many ways you could implement this - using a static utility method as above, or adding a HasSCIFIO layer on top of <a href="https://github.com/scijava/scijava-common/blob/master/src/main/java/org/scijava/AbstractContextual.java">AbstractContextual</a> classes (which we actually had at one point and then moved away from), etc...<br>
<br></div><div>Hope this helps. Let me know if anything is unclear.<br><br></div><div>- Mark<br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Tue, Jan 14, 2014 at 4:43 AM, Christian Dietz <span dir="ltr"><<a href="mailto:christian.dietz@uni-konstanz.de" target="_blank">christian.dietz@uni-konstanz.de</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
<div>Hi Mark,<br>
<br>
maybe a very stupid questions, but I got two more very general
ones:<br>
<br>
* If I want to use a global "Context" in my complete "KNIME
Application", why is there the possibility to create several
contexts?<br>
* How can I use the class "Scifio" in a global way, s.t. this
context also knows all other services? The "Scifio" Context class
itself suggests to create one context for ImageJ2, one for SCIFIO,
etc.?!<br>
<br>
Don't misunderstand me, I really want to use the context the way
you guys think its best, but I understand too little since now I
guess :)<br>
<br>
Have a nice day!<br>
<br>
Christian<br>
<br>
<br>
Am 13.01.2014 17:34, schrieb Mark Hiner:<br>
</div><div><div class="h5">
<blockquote type="cite">
<div dir="ltr">
<div class="gmail_extra">Hi Christian,</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Sat, Jan 11, 2014 at 12:05 PM,
Christian Dietz <span dir="ltr"><<a href="mailto:christian.dietz@uni-konstanz.de" target="_blank">christian.dietz@uni-konstanz.de</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">If so, I thought about
an "exclude service" option in the Context? Something
like: Include all SingletonService, but if you include
them, make sure that they are of type ImageJService or
SCIFIOService or something like that? Or: The user can
provide a "ServiceFilter" Implementation where he can
exclude/Include certain services? I don't know if this
makes sense at all, just a naive thinking I guess.</blockquote>
<div><br>
</div>
<div>I understand what you're saying, but there are
significant problems with excluding services like this.
It's really not extensible - it will always be possible
for something downstream to add a problematic service.
Unless you have complete control of the classpath - but if
you have that, you can limit which services and plugins
are discovered, and thus loaded, anyway.<br>
<br>
</div>
<div>So let's go more into the philosophy of what you're
trying to do:<br>
<br>
</div>
<div>- Why severely limit Services available to the Context?
From what I understood (and please correct me if I'm wrong
here) you have one class loader and one context per
plugin? So you want to limit the number of services
because each plugin is going to load a new context? Is
that right?<br>
<br>
</div>
<div>If so, I feel like the Context use is a bit too
narrowly scoped here. It's developed as more of an
application-level context, so I think it will be a
continuous struggle to use it as something else. Would it
be possible to refactor your context usage to simply have
one Context, that loads all of the services/plugins
available, and is then passed around/reused by other
modules?<br>
</div>
</div>
</div>
<br>
<div> Thanks,<br>
Mark<br>
</div>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Sat, Jan 11, 2014 at 12:05 PM,
Christian Dietz <span dir="ltr"><<a href="mailto:christian.dietz@uni-konstanz.de" target="_blank">christian.dietz@uni-konstanz.de</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
<div>Hi Mark,<br>
<br>
I figured out my problem and I have no clue how to solve
it in a nice way :-)<br>
<br>
We restrict our the context we create to very limited
amount of services. We only want to load the services we
really need. <br>
Since now, I told my Context to load all
SingletonService.class. I needed to load all
SingletonServices, such that the method
isMultipleChoiceObject (line 382) returns "true" for
e.g. the "CalculatorOp" and KNIME can generate the
dialog for e.g. the ImageCalculator. This only worked if
the CalculatorService.class is available in the context.<br>
<br>
The important part actually is: If I request to load
_any_ SingletonService, of course also the
SingletonServices from SCIFIO etc are also loaded, which
I actually don't need here. On the other hand, I don't
want to manually add SingletonServices from ImageJ2 I
need (this is what I do now with CalculatorSerice,
ThresholdService, etc... see line 128/129 at
<a href="https://github.com/knime-ip/knip-imagej2/blob/master/org.knime.knip.imagej2.core/src/org/knime/knip/imagej2/core/IJGateway.java" target="_blank">https://github.com/knime-ip/knip-imagej2/blob/master/org.knime.knip.imagej2.core/src/org/knime/knip/imagej2/core/IJGateway.java</a>).<br>
<br>
Does this make sense?<br>
<br>
If so, I thought about an "exclude service" option in
the Context? Something like: Include all
SingletonService, but if you include them, make sure
that they are of type ImageJService or SCIFIOService or
something like that? Or: The user can provide a
"ServiceFilter" Implementation where he can
exclude/Include certain services? I don't know if this
makes sense at all, just a naive thinking I guess.<br>
<br>
Thanks for your support again,<br>
<br>
Christian
<div><br>
<br>
<br>
Am 10.01.2014 19:57, schrieb Mark Hiner:<br>
</div>
</div>
<blockquote type="cite">
<div dir="ltr">
<div>
<div>
<div>
<div>
<div>OK, so I'm questioning how the <a href="https://github.com/knime-ip/knip-imagej2/blob/master/org.knime.knip.imagej2.core/src/org/knime/knip/imagej2/core/IJGateway.java#L428" target="_blank">IJAdapterProvider</a>
assembles the list of services..
<div>
<div><br>
<br>
It seems like it's trying to manually
assemble a list of services to construct
the context with. Is that right? When
constructing the context and providing a
list of services, you basically can give
it just the superclass services, and all
children will be discovered. We did that
so you can make a context with say
SCIFOService and SciJavaService and then
plugins that add more SCIFIOServices
will automatically be included.<br>
<br>
Does that make sense?<br>
<br>
</div>
</div>
</div>
<div>
<div> So I would possibly
refactor this to make a context with
ImageJServices, SCIFIOServices, and
SciJavaServices.. because those are the
relevant components you're using, right?<br>
<br>
</div>
</div>
</div>
<div>
<div> Also, yes whenever you try to
get objects from an ObjectIndex, ALL pending
initializations occur. This just defers the
initialization until it's required.<br>
<br>
</div>
</div>
</div>
<div>
<div> All SingletonServices add each
of their singleton instances to the
ObjectIndex lazily during their initialize()
method. So that's why these translators are
being loaded. And they fail because
SCIFIOServices aren't included.<br>
<br>
So, context creation is part of the problem..
but I think the classpath/class loader is
still incorrect, because you have OME-Formats
stuff in it.<br>
<br>
I will try to update the Context so that when
that error comes up, it prints out the
services that WERE used to create the context,
and maybe the classpath of the current class
loader. Because that error is extremely
cryptic and unhelpful.<br>
<br>
Then maybe we can discuss more tomorrow!<br>
<br>
</div>
</div>
</div>
Take care<br>
</div>
Mark<br>
</div>
</blockquote>
<br>
</div>
</blockquote>
</div>
<br>
</div>
</blockquote>
<br>
</div></div></div>
</blockquote></div><br></div>