Open report of iReport with JSF app.

gistfile1.java

  	HttpServletRequest request = (HttpServletRequest) FacesContext.getCurrentInstance().getExternalContext().getRequest();
    	
    	FuncUtil.apagarArquivos(request);
		
        String pathJasper = request.getRealPath("WEB-INF/classes/relatorio"); // local onde esta o relatorio 
        
        String os = System.getProperty("os.name");	
        File pasta = new File((os.toLowerCase().indexOf("linux") > -1 ? "/" : "\\"));
        
        pathJasper += pasta; 
        
        JasperReport jasperReport = (JasperReport) JRLoader.loadObject(pathJasper + "/NOME_DO_RELATORIO_COMPILADO.jasper");

        if (jasperReport == null)
        {
           FacesContext.getCurrentInstance().addMessage(null, new FacesMessage(FacesMessage.SEVERITY_WARN, "Erro ao gerar ...", null));
        }
        
        Map parameters = new HashMap();        
        parameters.put("parametro1", 14); //parametros q serao enviados        

      
        String urlBd ="url conexao", userBd = "postgres", senhaBd = "postgres";
      
    	Connection con = (Connection) DriverManager.getConnection(urlBd, userBd, senhaBd);
    	
    	JasperPrint impressao = JasperFillManager.fillReport(jasperReport, parameters, con);
        
        String pathPdf =  "/temp/"  //crie uma pasta temp dentro de webContent caso nao exista para gerar os relatorios nela
        				  + request.getRequestedSessionId()
                          + String.valueOf(Math.random() * 10000)
                          + "DESCRICAO_QUALQUER_PARA_O_PDF_COLOQUE_O_NOME_DO_REL_PRA_FACILITAR"
                          + ".pdf";
        
         JasperExportManager.exportReportToPdfFile(impressao, request.getRealPath("") + pathPdf);
       
         HttpServletResponse response = (HttpServletResponse) FacesContext.getCurrentInstance().getExternalContext().getResponse();
         response.sendRedirect(request.getContextPath() + pathPdf);