public class CellFunLong2DateStr implements J4ECellToExcel {

    @Override
    public Object toExecl(Object fieldVal) {
        Long createAt = Castors.me().castTo(fieldVal, Long.class);
        Date dateAt = new Date(createAt*1000);
        return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(dateAt);
    }

}

    @Column
    @Comment("报名时间")
    @J4EDefine(type = J4EColumnType.STRING)
    @J4ECell(toExcel = CellFunLong2DateStr.class)
    @J4EName("报名时间")
    @ColDefine(type = ColType.INT)
    private Integer createAt;