JasperSoft iReport Designer does not open when using only Java from Oracle, not Apple
I think this Running iReport on OS/X with Oracle JDK7  may be telling you that it isn't compatible with Oracle's Java.

You can download the last OS X Java release (see Java for OS X 2014-001) which is usable on OS X 10.7/.8/.9.

It appears you could then use jdkhome to point to the Apple Java release.