How to debug java applications without source. Follow

hi

i have a complex program that has so many jars and has a main jar loading and using them. I need to find a vulnerability in it.

what i want to o is that i import the whole directory of this app into intellij and start debugging.

so far i can only break on "method breakpoints"; i thing its because of messed up line numbers. googled a lot but there are some old stuff about it and I'm really frustrated at this point.

i want to see if source level is possible in this situation or not, if not, can i put BP in middle of methods in bytecode level or not.