Error 500--Internal Server Error + EBS

Just to put it on a context my developer had me deploy his java file to prod. Of course being a good DBA never promote anything on PROD that you do not understand. I asked him how he did it on dev and he said that the other DBA should know. I asked the other DBA what did he do. He sent me a couple of commands that he did not understand to. So putting faith on this guy I go ahead and test in on the test environment.

I followed the steps and bounced the middle tier. There was no errors on the logs and all the steps returned success. When I was about to call it a day I tried to logon to EBS. There it is, Error 500, which by itself was useless. I tried to bounce it a couple more times, sometimes that work. Unfortunately it did not this time. I tried to retrace my steps and revert all the files that I backed up. Yes BACKUP everything!!! I cannot emphasize it more, it saved me from tough spot. Still it did not work. I was really close on cloning it from another environment.

During my research I found this.

A quick test is to use this 

http://host.domain:port/OA_HTML/jsp/fnd/aoljtest.jsp 

example 

http://rend.ecp.priv:8010/OA_HTML/jsp/fnd/aoljtest.jsp 

For my case this solved it
 cd $FND_TOP/patch/115/bin
     ojspCompile.pl --compile --flush

See this note.
R12: Troubleshooting 500 Internal Server Error in Oracle E-Business suite (Doc ID 813523.1)