Upload só funciona uma vez

Front-end
#1

seguinte pessoal,faço a o upload do excel…leio ele e gravo as info no banco, se logo em seguinte tento fazer mesma coisa de novo ele nao chega a nem entra no metodo do upload…

olhem o codigo

  XHTML

   <h:form id="form" prependId="false" enctype="multipart/form-data"
			style="font-size: 10px">

        <p:fileUpload id="uploader" fileUploadListener="#{ledgerMB.upload}" mode="advanced"
				dragDropSupport="false" value="#{ledgerMB.uploadedFile}"
				update="tabView, messages" />

</h:form>
         Bean

    @ViewScoped
    public class LedgerMB implements Serializable {
   
    public void upload(FileUploadEvent event) {
//
		try {
			if (!isXls(event)){
				return;
			}
			DateFormat sdf = new SimpleDateFormat("HH:mm:ss");
			Ledger obj;
			VigenciaDAO daoVigencia = new VigenciaDAO();
			Vigencia vigencia = daoVigencia.recuperarVigenciaAtiva();
			String erro = null;
			logger.info("Lendo arquivo: " + event.getFile().getFileName());
			for (int i = 1; i < sh.getLastRowNum(); i++) {
				Row row = sh.getRow(i);

				if (row == null) {
					break;
				}

				if (row.getCell(7) == null) {
					break;
				}else if (row.getCell(7).getStringCellValue().length()<1){
					break;
				}

				obj = new Ledger();
				
				try{

					obj.setDocumentType(row.getCell(0) != null ? row.getCell(0).getStringCellValue() : null);
					if (row.getCell(1)!=null && row.getCell(1).getCellType()!=Cell.CELL_TYPE_STRING) {
						row.getCell(1).setCellType(Cell.CELL_TYPE_STRING);
					}
					obj.setRefDocument(row.getCell(1)!=null ? row.getCell(1).getStringCellValue():null);
				

					obj.setHashId("" + obj.hashCode());
					obj.setVigencia(vigencia);
					obj.setStatus(Status.ATIVO);


					listaTemp.add(obj);
					logger.info("Concluída leitura da linha: " + row.getRowNum());
					
				} catch (IllegalStateException e) {
					erro = "Reading file error in row: " + row.getRowNum()+1 + "and Column: " + i+1 + ". Possible cause: " + e.getMessage();
					logger.error(erro + "\n Arquivo:\t" + event.getFile().getFileName(), e);
					break;
				} catch (Exception e) {
					erro = "Reading file error in row: " + row.getRowNum() +1 + ". Possible cause: " + e.getMessage();
					logger.error(erro + "\n Arquivo:\t" + event.getFile().getFileName(), e);
					break;
				} 
			}
			logger.info("Leitura de arquivo: " + event.getFile().getFileName() + " finalizada com " + listaTemp.size() + " registros.");
			if (erro!=null){
				MessagesUtil.exibeMensagem(erro , "Upload Error", false);
			}
			

		}   catch (Exception e) {
			logger.error(e.getMessage(), e);
			MessagesUtil.exibeMensagem(e.getMessage(),	"Upload Error", false);
                       
		}
                
	}



       //verifica se atende o padrao
       public boolean isXls(FileUploadEvent event) throws IOException {
		if (event == null || event.getFile() == null) {
			MessagesUtil.exibeMensagem(
					"Invalid file.",
					"Error on loading file", false);
			return false;
		}

		String contentType = event.getFile().getContentType();

		if (!(contentType.equalsIgnoreCase(TYPE_XLS)
				|| contentType.equalsIgnoreCase(TYPE_XLSX)|| contentType.equalsIgnoreCase(TYPE_UNIX))) {
			MessagesUtil.exibeMensagem(
					"Invalid file type.",
					"Error on loading file", false);
			return false;
		}

		switch (contentType) {

			case TYPE_XLS:
	
			case TYPE_UNIX:
			HSSFWorkbook wb = new HSSFWorkbook(event.getFile().getInputstream());
			sh = wb.getSheetAt(0);
				break;
	
			case TYPE_XLSX:
			XSSFWorkbook sx = new XSSFWorkbook(event.getFile().getInputstream());
			sh = sx.getSheetAt(0);
				break;
	
			default:
				throw new InvalidFileNameException(contentType,
						"Invalid file type.");
		}
		
		
		try {
			if (validaExcel.compararLedger(sh.getRow(0))) {
				MessagesUtil.exibeMensagem(
						"Columns incompatibles with defined layout",
						"Invalid Columns", false);
				return false;
			}
		} catch (Exception e) {
			logger.error(e.getMessage(), e);
			return false;
		}

		return true;

	}

public void limpar(ActionEvent event) {
		listaTemp.clear();
		setListaFilter(null);
		setListaTempFilter(null);
		setUploadedFile(null);
	}

	public void gravar(ActionEvent event) {

		int i = dao.inserir(listaTemp);

		if (i > 0) {
			limpar(event);
			carregarLista();
			MessagesUtil.exibeMensagem(i + " row(s) inserted successfully.",
					"Ledger", true);

			if (lista == null || lista.isEmpty()) {
				MessagesUtil.exibeMensagem("Error on loading data.", "", false);
			}
		} else {
			MessagesUtil.exibeMensagem("No registry was inserted.",
					"Data writing", false);
		}
	}



      


   }
#2