I am adding my code here, JRPdfExporter not showing turkish characters.
JRPdfExporter pdfExporter = new JRPdfExporter();
response.setHeader("Content-Disposition","attachment;filename=\""+fileName+".pdf\""); //No I18N
response.setContentType("application/pdf"); //NO I18N
pdfExporter.setParameter( JRExporterParameter.JASPER_PRINT, jasperPrint );
pdfExporter.setParameter( JRExporterParameter.OUTPUT_STREAM, ouputStream );
pdfExporter.setParameter( JRExporterParameter.CHARACTER_ENCODING, "UTF-8" );
pdfExporter.exportReport();