Solution for working with modal window and JasperReport / iReport. / Solução para se trabalhar com janela modal e JasperReport/iReport.

JasperReportWithWindowModal.java

public void gerarReport(String filePath, List list) throws Exception {
        
        JDialog dialogReport = new JDialog(new javax.swing.JFrame(), "TITLE REPORT", true);
        dialogReport.setSize(1000, 700);
        dialogReport.setLocationRelativeTo(null);
        
        InputStream fileReport = getClass().getResourceAsStream(filePath);
        Map params = new HashMap();
        JRBeanCollectionDataSource dataList = new JRBeanCollectionDataSource(list);
        JasperPrint print = JasperFillManager.fillReport(fileReport, params, dataList);
        JasperViewer windowJasper = new JasperViewer(print, true);
        dialogReport.getContentPane().add(windowJasper.getContentPane());
        
        if ( print.getPages().size() > 0 )
            dialogReport.setVisible(true);
        else
            throw new Exception("No Pages!");
    }