by Gareth J Barnard.
Dear Luis,
From a Java point of view I think you have the solution. However, looking at the debug of lines 1954 and 4250 of 'filelib.php' it could be that the jar file mime type is not allowed. To check this, try seeing if the URL 'http://localhost/pluginfile.php/25/mod_ejsapp/jarfile/5/ejs_FallingBall.jar' works and serves the file. At least, any error may point in the right direction. Also examine the line numbers in your Moodle version's filelib.php.
Cheers,
Gareth