Cosmos, Is this the first time you have tried creating a java stored procedure using JDeveloper? Did you deploy it using the JDeveloper wizards?
Personally, I don't like using the wizards because:
I don't know what the wizard is doing
I don't know what to do and where to start looking when something goes wrong
In any case, I'm guessing that "MAILSEND" is the name of your stored procedure, and if I remember correctly, the JDeveloper wizards always wrap stored procedures in packages (but I forget where the wizard gets the package name from). So you may simply need to prefix the invocation of MAILSEND with its package name. For example, if the package name is COSMOS, then the invocation needs to be:
It may also be that you haven't (or should I say the JDeveloper wizards haven't) granted the required permissions to the MAILSEND procedure.
Have you checked the data dictionary (of the Oracle database) to see whether MAILSEND exists, is valid, and has the correct permissions?
Have you tried the JDeveloper forum (part of Oracle's OTN Web site?