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Installed Extensions don't work

 
 
Rhino
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      04-05-2004
Is there some trick to making Installed Extensions work?

I'm trying to follow the instructions in the "The Extension Mechanism" trail
of the Java Tutorial but I'm running into problems with Installed
Extensions. Download Extensions are working just fine but I can't get
Installed Extensions to work at all. It's as if the jre/lib/ext directory
isn't there at all. I think I've followed all of the instructions carefully
and accurately but the Installed Extensions just won't work.

I know that is a fairly skimpy description of the problem but I'm hoping
that someone will suggest some basic possibilities before we get into all
the details. For instance, my JDK is on the PATH but the jre/lib/ext isn't
specified in the PATH. I assume that c:\j2sdk1.4.1_02\bin in the PATH also
enables programs to see down to c:\j2sdk1.4.1_02\jre\lib\ext but perhaps
that's wrong and I need to ensure that the jre/lib/ext is specifically named
in the PATH. Nothing is said about PATH in this trail though so I may be
going in the wrong direction with this suspicion.

Can anyone suggest a way to verify that Installed Extensions work?

For what it's worth, I actually tried the example suggested in the trail but
it wouldn't compile. As basic as it was, I couldn't make it compile and
can't see how it could possibly compile without one change: the
instantiation of an object named RectangleArea. That makes me wonder if
there are other basic things that are omitted from the trail.

I've tried several different examples of varying complexities but none of
them will work for me.

Any suggestions about basic things to look at to diagnose this situation?


--
Rhino
---
rhino1 AT sympatico DOT ca
"If you're getting something for nothing, you're not using your own credit
card."


 
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Roedy Green
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      04-05-2004
On Mon, 5 Apr 2004 00:00:45 -0400, "Rhino"
<(E-Mail Removed)> wrote or quoted :

>the jre/lib/ext directory


there are at least two of them, one embedded in the JDK and one in
program files. For safety, add your jars to both.

--
Canadian Mind Products, Roedy Green.
Coaching, problem solving, economical contract programming.
See http://mindprod.com/jgloss/jgloss.html for The Java Glossary.
 
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Rhino
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      04-05-2004
Your solution was exactly what I needed; everything works now. Thank you!

Now, could you explain it to me?
1. Why is the second JRE (the one in Program Files) even there? I don't
remember installing it.
2. When does the second JRE get used by my system/programs?
3. Does this mean I should ignore the first JRE, the one under
c:\j2sdk1.4.1_02 altogether? If not, when should I be using it?

Grateful but confused,

Rhino

"Roedy Green" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> On Mon, 5 Apr 2004 00:00:45 -0400, "Rhino"
> <(E-Mail Removed)> wrote or quoted :
>
> >the jre/lib/ext directory

>
> there are at least two of them, one embedded in the JDK and one in
> program files. For safety, add your jars to both.
>
> --
> Canadian Mind Products, Roedy Green.
> Coaching, problem solving, economical contract programming.
> See http://mindprod.com/jgloss/jgloss.html for The Java Glossary.



 
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Mark Thornton
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Posts: n/a
 
      04-10-2004
Rhino wrote:

> Is there some trick to making Installed Extensions work?
>
> I'm trying to follow the instructions in the "The Extension Mechanism" trail
> of the Java Tutorial but I'm running into problems with Installed
> Extensions. Download Extensions are working just fine but I can't get
> Installed Extensions to work at all. It's as if the jre/lib/ext directory
> isn't there at all. I think I've followed all of the instructions carefully
> and accurately but the Installed Extensions just won't work.
>
> I know that is a fairly skimpy description of the problem but I'm hoping
> that someone will suggest some basic possibilities before we get into all
> the details. For instance, my JDK is on the PATH but the jre/lib/ext isn't
> specified in the PATH. I assume that c:\j2sdk1.4.1_02\bin in the PATH also
> enables programs to see down to c:\j2sdk1.4.1_02\jre\lib\ext but perhaps
> that's wrong and I need to ensure that the jre/lib/ext is specifically named
> in the PATH. Nothing is said about PATH in this trail though so I may be
> going in the wrong direction with this suspicion.
>
> Can anyone suggest a way to verify that Installed Extensions work?
>
> For what it's worth, I actually tried the example suggested in the trail but
> it wouldn't compile. As basic as it was, I couldn't make it compile and
> can't see how it could possibly compile without one change: the
> instantiation of an object named RectangleArea. That makes me wonder if
> there are other basic things that are omitted from the trail.
>
> I've tried several different examples of varying complexities but none of
> them will work for me.
>
> Any suggestions about basic things to look at to diagnose this situation?
>
>


Prior to 1.5, java looks for extensions as you expect, but javac does
NOT. So to compile code using such extensions you have to add them
explicitly to the classpath, but you can execute the result without
having the extensions in the classpath.

Mark Thornton


 
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