For turkish character support, you chould choose the international global UTF-8 format.
In IntelliJIdea
**File / Settings / Editor / File Encoding** / *.properties
Choose -> **Default encoding for properties files UTF-8
By the use of BOM configurations you can find the correct solution for your files. Do not forget that some choices of BOM for some class files can cause various \uxxxx errors like '\ufeff' error
Moreover you could choose also Global Encoding and Project encoding values just given above in the same tab as UTF-8 to get a more general solution for the future projects.
Screenshot of the web content created by the use of many components bfrom messages.properties
printed text or response from local server with turkish characters
Settings Page