Bonjour tout le monde ,
j'utilise POI, j'arrive à générer un fichier excel, mais lorsque je veux insérer une date de dans une colonne par le code :
//Date premiere Activation.
row = sheet.getRow(10);
cell = row.getCell((short)1);
cell.setCellType(HSSFCell.CELL_TYPE_STRING);
cell.setCellValue(dto.getDatePremiereActivation());

dto.getDatePremiereActivation() ets de type java.util.date, j'obtient l'exception suivante :

Caused by: java.lang.NullPointerException
at java.util.Calendar.setTime(Ljava/util/DateV(Calendar.java:902)
at org.apache.poi.hssf.usermodel.HSSFDateUtil.getExcelDate(Ljava/util/DateD(HSSFDateUtil.java:64)
at org.apache.poi.hssf.usermodel.HSSFCell.setCellValue(Ljava/util/DateV(HSSFCell.java:612)
at com.francetelecom.webvpn.services.rapportsEtatParc.GererRapportsEtatParcImpl.convertToReseau(Lorg/apache/poi/hssf/usermodel/HSSFWorkbook;Lcom/francetelecom/webvpn/services/rapportsEtatParc/RapportsEtatParcDTOLorg/apache/poi/hssf/usermodel/HSSFWorkbook;(GererRapportsEtatParcImpl.java:348)
at com.francetelecom.webvpn.services.rapportsEtatParc.GererRapportsEtatParcImpl.scExporterReports(Lcom/francetelecom/webvpn/services/rapportsEtatParc/RapportsEtatParcDTOLjava/io/File;(GererRapportsEtatParcImpl.java:159)
at java.util.Calendar.setTime(Ljava/util/DateV(Calendar.java:902)
at org.apache.poi.hssf.usermodel.HSSFDateUtil.getExcelDate(Ljava/util/DateD(HSSFDateUtil.java:64)
at org.apache.poi.hssf.usermodel.HSSFCell.setCellValue(Ljava/util/DateV(HSSFCell.java:612)
at com.francetelecom.webvpn.services.rapportsEtatParc.GererRapportsEtatParcImpl.convertToReseau(Lorg/apache/poi/hssf/usermodel/HSSFWorkbook;Lcom/francetelecom/webvpn/services/rapportsEtatParc/RapportsEtatParcDTOLorg/apache/poi/hssf/usermodel/HSSFWorkbook;(GererRapportsEtatParcImpl.java:348)
at com.francetelecom.webvpn.services.rapportsEtatParc.GererRapportsEtatParcImpl.scExporterReports(Lcom/francetelecom/webvpn/services/rapportsEtatParc/RapportsEtatParcDTOLjava/io/File;(GererRapportsEtatParcImpl.java:159)
at jrockit.reflect.NativeMethodInvoker.invoke0(Ljava/lang/Object;ILjava/lang/Object;[Ljava/lang/ObjectLjava/lang/Object;(Unknown Source)
at jrockit.reflect.NativeMethodInvoker.invoke(Ljava/lang/Object;[Ljava/lang/ObjectLjava/lang/Object;(Unknown Source)
at jrockit.reflect.VirtualNativeMethodInvoker.invoke(Ljava/lang/Object;[Ljava/lang/ObjectLjava/lang/Object;(Unknown Source)
at java.lang.reflect.Method.invoke(Ljava/lang/Object;[Ljava/lang/Object;I)Ljava/lang/Object;(Unknown Source)
at com.francetelecom.webvpn.service.ServiceManager.invoke(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/ObjectLjava/lang/Object;(ServiceManager.java:144)
at $Proxy13.scExporterReports(Lcom/francetelecom/webvpn/services/rapportsEtatParc/RapportsEtatParcDTOLjava/io/File;(Unknown Source)
at com.francetelecom.webvpn.struts.RapportsEtatParcAction.extraireRapportReseaux(Lorg/apache/struts/action/ActionMapping;Lorg/apache/struts/action/ActionForm;Ljavax/servlet/http/HttpServletRequest;Ljavax/servlet/http/HttpServletResponseLorg/apache/struts/action/ActionForward;(RapportsEtatParcAction.java:118)
at jrockit.reflect.NativeMethodInvoker.invoke0(Ljava/lang/Object;ILjava/lang/Object;[Ljava/lang/ObjectLjava/lang/Object;(Unknown Source)
at jrockit.reflect.NativeMethodInvoker.invoke(Ljava/lang/Object;[Ljava/lang/ObjectLjava/lang/Object;(Unknown Source)
at jrockit.reflect.VirtualNativeMethodInvoker.invoke(Ljava/lang/Object;[Ljava/lang/ObjectLjava/lang/Object;(Unknown Source)
at java.lang.reflect.Method.invoke(Ljava/lang/Object;[Ljava/lang/Object;I)Ljava/lang/Object;(Unknown Source)

il faut faire une conversion des dates?.
merci pour votre aide.