数据查询: 传递的时间是字符串时间(202107) 需要拿到前两个月的时间(也就是要以202105的时间去查询数据)

两种解决方案:

1. 在sql语句层面取到指定的时间来进行业务处理

   select to_date('20161230','yyyymmdd')-to_date('20161201','yyyymmdd') from dual;
   

2. 通过Java代码层面, 首先可以写个方法, 拿到上个月的时间, 然后再调用一下, 就可以拿到上上个月的时间;

   package com.biostime.merchant.wx;
   
   import com.biostime.merchant.wx.exception.MerchantWxException;
   import org.apache.commons.lang.StringUtils;
   
   import java.text.SimpleDateFormat;
   import java.util.Calendar;
   import java.util.Date;
   
   /**
    * @author TongHu
    * @date 2021/7/30 - 14:09
    */
   public class TestDate {
       public static void main(String[] args)throws Exception {
           String lastYearMonthByYearMonth = getLastYearMonthByYearMonth(null);
           System.out.println("lastYearMonthByYearMonth = " + lastYearMonthByYearMonth);
           String lastYearMonthByYearMonth1 = getLastYearMonthByYearMonth(lastYearMonthByYearMonth);
           System.out.println("lastYearMonthByYearMonth1 = " + lastYearMonthByYearMonth1);
   
       }
   
       public static String getLastYearMonthByYearMonth(String yearMonth) throws Exception{
           SimpleDateFormat format = new SimpleDateFormat("yyyyMM");
           Date date = null;
           try {
               if (StringUtils.isNotBlank(yearMonth)) {
                   date = format.parse(yearMonth);
               }
               else {
                   date = new Date();
               }
               Calendar calendar = Calendar.getInstance();
               calendar.setTime(date); // 设置为当前时间
               calendar.set(Calendar.MONTH, calendar.get(Calendar.MONTH) - 1); // 设置为上一个月
               date = calendar.getTime();
               String accDate = format.format(date);
               return accDate;
           } catch (Exception e) {
               throw new MerchantWxException("日期格式有误");
           }
       }
   }
   package com.biostime.merchant.wx;
   
   import com.biostime.merchant.wx.exception.MerchantWxException;
   import org.apache.commons.lang.StringUtils;
   
   import java.text.SimpleDateFormat;
   import java.util.Calendar;
   import java.util.Date;
   
   /**
    * @author TongHu
    * @date 2021/7/30 - 14:09
    */
   public class TestDate {
       public static void main(String[] args)throws Exception {
           String lastYearMonthByYearMonth = getLastYearMonthByYearMonth(null);
           System.out.println("lastYearMonthByYearMonth = " + lastYearMonthByYearMonth);
           String lastYearMonthByYearMonth1 = getLastYearMonthByYearMonth(lastYearMonthByYearMonth);
           System.out.println("lastYearMonthByYearMonth1 = " + lastYearMonthByYearMonth1);
   
       }
   
       public static String getLastYearMonthByYearMonth(String yearMonth) throws Exception{
           SimpleDateFormat format = new SimpleDateFormat("yyyyMM");
           Date date = null;
           try {
               if (StringUtils.isNotBlank(yearMonth)) {
                   date = format.parse(yearMonth);
               }
               else {
                   date = new Date();
               }
               Calendar calendar = Calendar.getInstance();
               calendar.setTime(date); // 设置为当前时间
               calendar.set(Calendar.MONTH, calendar.get(Calendar.MONTH) - 1); // 设置为上一个月
               date = calendar.getTime();
               String accDate = format.format(date);
               return accDate;
           } catch (Exception e) {
               throw new MerchantWxException("日期格式有误");
           }
       }
   }