前言

在我们日常开发过程中，当涉及到处理日期和时间的操作时，字符串与Date日期类往往要经过相互转换，且在SQL语句的动态查询中，往往月份的格式不正确，SQL语句执行的效果是不同的：
例如，如果我们想查询某年某月的所有订单,如果不能动态的获取到当月的天数信息（例如4月的区间查询必须是[1-30]），是查询不出来结果的，这时候就需要我们在后端动态的根据当月天数，查询当月有多少天，完成关于月份的动态查询：
四月的订单有一条：

如果我们把区间单位设置为31，是查不到一条信息的：

区间在30就可以：

DateUtils日期工具类

/*** 日期操作工具类*/
public class DateUtils {/*** 日期转换-  String -> Date** @param dateString 字符串时间* @return Date类型信息* @throws Exception 抛出异常*/public static Date parseString2Date(String dateString) throws Exception {if (dateString == null) {return null;}return parseString2Date(dateString, "yyyy-MM-dd");}/*** 日期转换-  String -> Date** @param dateString 字符串时间* @param pattern    格式模板* @return Date类型信息* @throws Exception 抛出异常*/public static Date parseString2Date(String dateString, String pattern) throws Exception {if (dateString == null) {return null;}SimpleDateFormat sdf = new SimpleDateFormat(pattern);Date date = sdf.parse(dateString);return date;}/*** 日期转换 Date -> String** @param date Date类型信息* @return 字符串时间* @throws Exception 抛出异常*/public static String parseDate2String(Date date) throws Exception {if (date == null) {return null;}return parseDate2String(date, "yyyy-MM-dd");}/*** 日期转换 Date -> String** @param date    Date类型信息* @param pattern 格式模板* @return 字符串时间* @throws Exception 抛出异常*/public static String parseDate2String(Date date, String pattern) throws Exception {if (date == null) {return null;}SimpleDateFormat sdf = new SimpleDateFormat(pattern);String strDate = sdf.format(date);return strDate;}/*** 获取当前日期的本周一是几号** @return 本周一的日期*/public static Date getThisWeekMonday() {Calendar cal = Calendar.getInstance();cal.setTime(new Date());// 获得当前日期是一个星期的第几天int dayWeek = cal.get(Calendar.DAY_OF_WEEK);if (1 == dayWeek) {cal.add(Calendar.DAY_OF_MONTH, -1);}// 设置一个星期的第一天，按中国的习惯一个星期的第一天是星期一cal.setFirstDayOfWeek(Calendar.MONDAY);// 获得当前日期是一个星期的第几天int day = cal.get(Calendar.DAY_OF_WEEK);// 根据日历的规则，给当前日期减去星期几与一个星期第一天的差值cal.add(Calendar.DATE, cal.getFirstDayOfWeek() - day);return cal.getTime();}/*** 获取当前日期周的最后一天** @return 当前日期周的最后一天*/public static Date getSundayOfThisWeek() {Calendar c = Calendar.getInstance();int dayOfWeek = c.get(Calendar.DAY_OF_WEEK) - 1;if (dayOfWeek == 0) {dayOfWeek = 7;}c.add(Calendar.DATE, -dayOfWeek + 7);return c.getTime();}/*** 根据日期区间获取月份列表** @param minDate 开始时间* @param maxDate 结束时间* @return 月份列表* @throws Exception*/public static List<String> getMonthBetween(String minDate, String maxDate, String format) throws Exception {ArrayList<String> result = new ArrayList<>();SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM");Calendar min = Calendar.getInstance();Calendar max = Calendar.getInstance();min.setTime(sdf.parse(minDate));min.set(min.get(Calendar.YEAR), min.get(Calendar.MONTH), 1);max.setTime(sdf.parse(maxDate));max.set(max.get(Calendar.YEAR), max.get(Calendar.MONTH), 2);SimpleDateFormat sdf2 = new SimpleDateFormat(format);Calendar curr = min;while (curr.before(max)) {result.add(sdf2.format(curr.getTime()));curr.add(Calendar.MONTH, 1);}return result;}/*** 根据日期获取年度中的周索引** @param date 日期* @return 周索引* @throws Exception*/public static Integer getWeekOfYear(String date) throws Exception {Date useDate = parseString2Date(date);Calendar cal = Calendar.getInstance();cal.setTime(useDate);return cal.get(Calendar.WEEK_OF_YEAR);}/*** 根据年份获取年中周列表** @param year 年分* @return 周列表* @throws Exception*/public static Map<Integer, String> getWeeksOfYear(String year) throws Exception {Date useDate = parseString2Date(year, "yyyy");Calendar cal = Calendar.getInstance();cal.setTime(useDate);//获取年中周数量int weeksCount = cal.getWeeksInWeekYear();Map<Integer, String> mapWeeks = new HashMap<>(55);for (int i = 0; i < weeksCount; i++) {cal.get(Calendar.DAY_OF_YEAR);mapWeeks.put(i + 1, parseDate2String(getFirstDayOfWeek(cal.get(Calendar.YEAR), i)));}return mapWeeks;}/*** 获取某年的第几周的开始日期** @param year 年分* @param week 周索引* @return 开始日期* @throws Exception*/public static Date getFirstDayOfWeek(int year, int week) throws Exception {Calendar c = new GregorianCalendar();c.set(Calendar.YEAR, year);c.set(Calendar.MONTH, Calendar.JANUARY);c.set(Calendar.DATE, 1);Calendar cal = (GregorianCalendar) c.clone();cal.add(Calendar.DATE, week * 7);return getFirstDayOfWeek(cal.getTime());}/*** 获取某年的第几周的结束日期** @param year 年份* @param week 周索引* @return 结束日期* @throws Exception*/public static Date getLastDayOfWeek(int year, int week) throws Exception {Calendar c = new GregorianCalendar();c.set(Calendar.YEAR, year);c.set(Calendar.MONTH, Calendar.JANUARY);c.set(Calendar.DATE, 1);Calendar cal = (GregorianCalendar) c.clone();cal.add(Calendar.DATE, week * 7);return getLastDayOfWeek(cal.getTime());}/*** 获取当前时间所在周的开始日期** @param date 当前时间* @return 开始时间*/public static Date getFirstDayOfWeek(Date date) {Calendar c = new GregorianCalendar();c.setFirstDayOfWeek(Calendar.SUNDAY);c.setTime(date);c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek());return c.getTime();}/*** 获取当前时间所在周的结束日期** @param date 当前时间* @return 结束日期*/public static Date getLastDayOfWeek(Date date) {Calendar c = new GregorianCalendar();c.setFirstDayOfWeek(Calendar.SUNDAY);c.setTime(date);c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek() + 6);return c.getTime();}//获得上周一的日期public static Date geLastWeekMonday(Date date) {Calendar cal = Calendar.getInstance();cal.setTime(getThisWeekMonday(date));cal.add(Calendar.DATE, -7);return cal.getTime();}//获得本周一的日期public static Date getThisWeekMonday(Date date) {Calendar cal = Calendar.getInstance();cal.setTime(date);// 获得当前日期是一个星期的第几天int dayWeek = cal.get(Calendar.DAY_OF_WEEK);if (1 == dayWeek) {cal.add(Calendar.DAY_OF_MONTH, -1);}// 设置一个星期的第一天，按中国的习惯一个星期的第一天是星期一cal.setFirstDayOfWeek(Calendar.MONDAY);// 获得当前日期是一个星期的第几天int day = cal.get(Calendar.DAY_OF_WEEK);// 根据日历的规则，给当前日期减去星期几与一个星期第一天的差值cal.add(Calendar.DATE, cal.getFirstDayOfWeek() - day);return cal.getTime();}//获得下周一的日期public static Date getNextWeekMonday(Date date) {Calendar cal = Calendar.getInstance();cal.setTime(getThisWeekMonday(date));cal.add(Calendar.DATE, 7);return cal.getTime();}//获得今天日期public static Date getToday(){return new Date();}//获得本月一日的日期public static Date getFirstDay4ThisMonth(){Calendar calendar = Calendar.getInstance();calendar.set(Calendar.DAY_OF_MONTH,1);return calendar.getTime();}public static void main(String[] args) {try {System.out.println("本周一" + parseDate2String(getThisWeekMonday()));System.out.println("本月一日" + parseDate2String(getFirstDay4ThisMonth()));} catch (Exception e) {e.printStackTrace();}}//获取本月多少天public static int getmaxmonthdays(Date date){Calendar calendar = Calendar.getInstance();calendar.set(date.getYear(),date.getMonth(),date.getDate());return calendar.getActualMaximum(Calendar.DATE);}
}

总结

由于DateUtils 工具类中的方法都是静态的，是属于类的，所有在使用的过程中只需要用类型.方法名调用即可（DateUtils .getmaxmonthdays(Date date)），该工具类为我们提供了大量关于Date的方法，封装调用，提升变成性能的同时也降低程序的耦合性。