How to recovery this error: log4j:WARN No appenders could be found for logger (net.sf.jasperreports.extensions.ExtensionsEnvironment)

Question

I try to make report with ireport but i get this problem:

log4j:WARN No appenders could be found for logger(net.sf.jasperreports.extensions.ExtensionsEnvironment).
log4j:WARN Please initialize the log4j system properly.

My source:

private URL[] reports = new URL[]{
        getClass().getResource("/Laporan/LapGuru.Jasper"),
        getClass().getResource("/Laporan/LapGuruByNIP.Jasper"),};
        private URL urlCurrent;

    try{           

            Map parameter = new HashMap();

            parameter.put("nip",this.txtNIP.getText());
            InputStream os = null;
            os = urlCurrent.openStream();
            JasperReport jReport = (JasperReport)JRLoader.loadObject(os);
            JasperPrint jPrint = JasperFillManager.fillReport(jReport, parameter, ClassDB.getkoneksi());
            JRViewer viewer = new JRViewer(jPrint);
            viewer.setOpaque(true);
            viewer.setVisible(true);
            jScrollPane1.add(viewer);
            jScrollPane1.setViewportView(viewer);

            } catch (Exception ex)
            {
                System.out.println(ex);
            }

Answer 1

Make sure you have log4j.properties file in your classpath. There are also other options to configure log4j if you want to name however you want add a System property to the command line when you start Java, like this:

-Dlog4j.configuration=file:///path/to/your/log4j.properties

See the link http://logging.apache.org/log4j/1.2/manual.html#defaultInit