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In-Reply-To: <5F135B84.8070302@anastigmatix.net>
From: Kartik Ohri <kartikohri13@gmail.com>
Date: Sun, 19 Jul 2020 11:58:11 +0530
Message-ID: 
 <CAASLQ4O=tYGASWB6F+PTiB2L3RbmHcVX8XAbKHyhwBDOodH1zg@mail.gmail.com>
Subject: Re: PL/Java new build plugin
To: Chapman Flack <chap@anastigmatix.net>
Cc: pljava-dev@lists.postgresql.org
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>
> Aha! And it generates that using getPathFromArtifacts(), which just goes
> through its own dependency list and collects the jar names (which are
> maybe the exact same jar names its current ClassRealm loader is using).
>
> I wonder what would happen just making a dead-simple ClassLoader with
> two "parents" and otherwise no functionality of its own. Of course it
> could only have one real parent and an instance field for the 'extra' one.
>
> Create it so one 'parent' is the ClassRealm loader that loaded us, and the
> other is from getSystemClassLoader() (they changed the official name to
> "application class loader" but didn't rename the method). Have its
> findClass
> method just say "either parent A has it or parent B has it or I haven't
> heard of it, sorry."
>
> (In fact, findClass doesn't get called until the 'real' parent has already
> been checked, so it doesn't need to do anything besides check the 'extra'
> parent and return what it finds, if anything.)
>

There is an issue with calling findClass on the instance field because it
has protected visibility. loadClass on the other hand is public.

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<div dir="ltr"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Aha! And it generates that using getPathFromArtifacts(), which just goes<br>
through its own dependency list and collects the jar names (which are<br>
maybe the exact same jar names its current ClassRealm loader is using).<br>
<br>
I wonder what would happen just making a dead-simple ClassLoader with<br>
two &quot;parents&quot; and otherwise no functionality of its own. Of course it<br>
could only have one real parent and an instance field for the &#39;extra&#39; one.<br>
<br>
Create it so one &#39;parent&#39; is the ClassRealm loader that loaded us, and the<br>
other is from getSystemClassLoader() (they changed the official name to<br>
&quot;application class loader&quot; but didn&#39;t rename the method). Have its findClass<br>
method just say &quot;either parent A has it or parent B has it or I haven&#39;t<br>
heard of it, sorry.&quot;<br>
<br>
(In fact, findClass doesn&#39;t get called until the &#39;real&#39; parent has already<br>
been checked, so it doesn&#39;t need to do anything besides check the &#39;extra&#39;<br>
parent and return what it finds, if anything.)<br></blockquote><div><br></div><div>There is an issue with calling findClass on the instance field because it has protected visibility. loadClass on the other hand is public.</div></div></div>

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