java8 获取时间所在月的开始和结束时间

不加限制则小数点后有九位，由于数据库5.7版本后小数点后有6位，如果不限制则会查到超范围的数据，如下：

LocalDateTime startDateTime = LocalDateTime.now().with(TemporalAdjusters.firstDayOfMonth()).with(LocalTime.MIN);
    LocalDateTime endDateTime = LocalDateTime.now().with(TemporalAdjusters.lastDayOfMonth()).with(LocalTime.MAX);

LocalDateTime startDateTime = LocalDateTime.now().with(TemporalAdjusters.firstDayOfMonth()).with(LocalTime.MIN.withNano(999999000));
    LocalDateTime endDateTime = LocalDateTime.now().with(TemporalAdjusters.lastDayOfMonth()).with(LocalTime.MAX.withNano(999999000));