can't run my jarmake output

can't run my jarmake output

[John Dalbey]

JGNAT looks really neat so far ...

$ jgnatmake blastoff
jgnat -c blastoff.adb
jgnatbind -x blastoff.ali
jgnatlink blastoff.ali

$ java blastoff

Countdown to JGNAT ...
   10    9    8    7    6    5    4    3    2    1    0
BLASTOFF!


So my Ada code runs on the JVM ... Cool!

but I can't figure out how to run the .jar files produced by the jarmake
tool.

$ jarmake -oblastoff.jar blastoff.class

$ java -jar blastoff.jar
Failed to load Main-Class manifest attribute from
blastoff.jar

Isn't all that's necessary is to provide the -jar switch on the command
line? It is NOT an applet, so I don't use appletviewer. Am I missing
some basic concept here?

I couldn't find any reference to the word "manifest" in the user guide.
I'm stumped.

Thanks,
--jd

JGNAT: Re: can't run my jarmake output

[Geoff Bull]

John Dalbey wrote:
> 
> JGNAT looks really neat so far ...
> 
<neat stuff snipped>
> 
> but I can't figure out how to run the .jar files produced by the jarmake
> tool.
> 
> $ jarmake -oblastoff.jar blastoff.class
> 
> $ java -jar blastoff.jar
> Failed to load Main-Class manifest attribute from
> blastoff.jar


This is because jarmake doesn't add a manifest to the jarfile,
and looking at the source I couldn't see an option to make it do so
You could add one by:

Unpacking the jar file.

$  jar xvf blastoff.jar

Creating a manifest file:

$  echo "Main-Class: blastoff" > blastoff.manifest

Then rebuild the jarfile with the command:

$  jar cmf  blastoff.manifest new_blastoff.jar all_the_files_you extracted.
$  java -jar new_blastoff.jar
should work.

I think all_the_files_you extracted = blastoff.class ada_blastoff.class jgnat

I tried this with the hello example and it worked.

If there really is no way to make jarmake add a manifest
specifying the main class, then that is a major shortcoming.

There is another (better) way to work around this:
$  mkdir META-INF
$  echo "Main-Class: blastoff" > META-INF/MANIFEST.MF
$  jarmake -oblastoff.jar blastoff.class META-INF/MANIFEST.MF
$  java -jar blastoff.jar

Cheers
Geoff