Data file owner and group difficulties

[James T. Studebaker]

My servlets create data files.  The webapp is running on a Linux system.  The app user is jims and my group is jims.  I have to set permissions to 777 in order for tomcat to read data files.  When data files are created, the user is tomcat and the group is nobody.  As a result my servlets can not read the data files created.  Is the a configuration parameter that will result in data files created with a user of jims and a group of jims.  Is there configuration parameters that result in tomcat being able to read data files with the user jims and the group jims. Thank you James T. Studebaker