Como gerar relatório PDF em JSF 2.0

private Connection getConexao() throws SQLException, ClassNotFoundException{
           Connection con = null;
           try{
               Class.forName("org.postgresql.Driver");
               String url = "jdbc:postgresql://localhost:5432/nutec";
               String usuario = "root";
               String senha = "debian23";
               con = (Connection) DriverManager.getConnection(url,usuario,senha);
           }catch(SQLException sql){
               System.out.println("erro ao conectar");
                sql.printStackTrace();
           }
           return con;
       }

    public InputStreamDownload relAlunos(String turma) throws JRException, SQLException, ClassNotFoundException {
        InputStream file = getClass().getClassLoader().getResourceAsStream("/br/com/catequese/relatorio/relAlunos.jasper");
        Map parametros = new HashMap();
        parametros.put("turma", turma);
        ByteArrayOutputStream os = new ByteArrayOutputStream();
        JasperRunManager.runReportToPdfStream(file, os, parametros, getConexao());
        InputStream document = new ByteArrayInputStream(os.toByteArray());
    return new InputStreamDownload(document, "application/pdf", "relatorioAlunos.pdf", true, os.toByteArray().length);
    }