首先，根据时间生成，我们先要格式化一下时间格式
SimpleDateFormat dmfot = new SimpleDateFormat("yyyyMMdd");
//截取当前时间作为流水号
String preCode = dmfot.format(new Date());
然后我们进行数据库查询，今天最大的流水号是多少？
//获取最大编号
String maxCode = getMaxCode(date);
查询语句如下：
select Max(code)
from table_name
where
declare_time >= STR_TO_DATE(#{date},'%Y-%m-%d')
这里我们重置一下时间格式，获取当前时间零点
public static String getCurrentDay() {
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Calendar c = Calendar.getInstance();
c.setTime(new Date());
c.set(Calendar.HOUR_OF_DAY, 0);
c.set(Calendar.MINUTE, 0);
c.set(Calendar.SECOND, 0);
Date date = c.getTime();
String currentDay = format.format(date);
return currentDay;
}
查询之后进行判断，如果查出的数据为空，证明今天没有生成流水号，我们直接set
//设置流水号格式，根据实际情况设置
DecimalFormat num=new DecimalFormat("000");
if(maxCode != null && !"null".equals(maxCode)){
//对流水号截取后三位
String code = maxCode.substring(maxCode.length()-3,maxCode.length());
//例如后三位为002，通过以下步骤，将会变为003
int count = Integer.valueOf(code)+1;
String number = num.format(count);
return preCode + "-" + number;
}else {
return preCode + "-" + "001";
}
"001"；例如 20191017-001
第二种:1、使用redis原子自增特性
2、先判断key，是否存在
2.1、存在：顺序码自增
2.2、不存子：重新生成顺序码
代码实现 控制器import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
@RestController
@RequestMapping("/api/task/v1")
@Api(tags = "任务API 测试")
public class TaskController {
@Autowired
RedisService redisService;
public static final Long EXPIRE = 60 * 60 * (24 + 12) * 1L;
@ApiOperation("生成任务编号")
@GetMapping("generator")
public String generateTaskId() {
LocalDateTime localDateTime = LocalDateTime.now();
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yMMdd");
String key = dtf.format(localDateTime);
long incr;
if (redisService.exists(key)) {
incr = redisService.incr(key, EXPIRE);
} else {
incr = redisService.incr(key, EXPIRE);
}
return key.substring(key.length() - 5) + CommonUtil.automaticFilling((int) incr, 3);
}
}
redis工具类
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.ValueOperations;
import org.springframework.stereotype.Service;
import java.io.Serializable;
import java.util.concurrent.TimeUnit;
@Service
@Slf4j
public class RedisService {
@Autowired
private RedisTemplate redisTemplate;
private static double size = Math.pow(2, 32);
public boolean exists(final String key) {
return redisTemplate.hasKey(key);
}
public void remove(final String key) {
if (exists(key)) {
redisTemplate.delete(key);
}
}
public boolean set(final String key, Object value, Long expireTime) {
ValueOperations operations = redisTemplate.opsForValue();
operations.set(key, value);
redisTemplate.expire(key, expireTime, TimeUnit.SECONDS);
return true;
}
public Long incr(final String key, Long expireTime) {
ValueOperations operations = redisTemplate.opsForValue();
Long increment = operations.increment(key);
redisTemplate.expire(key, expireTime, TimeUnit.SECONDS);
return increment;
}
public Object get(final String key) {
Object result = null;
ValueOperations operations = redisTemplate.opsForValue();
result = operations.get(key);
return result;
}
}
自动补零工具类
import com.fasterxml.jackson.databind.ObjectMapper;
import lombok.extern.slf4j.Slf4j;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.security.MessageDigest;
import java.util.Random;
import java.util.UUID;
@Slf4j
public class CommonUtil {
public static String automaticFilling(int code, int num) {
return String.format("%0" + num + "d", code);
}
}
计算时间差
用SimpleDateFormat类：
计算两个Date之间的时间差，基本思路为把Date转换为ms(微秒)，然后计算两个微秒时间差。时间的兑换规则如下
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class Time {
public static void main(String[] args){
String start="2021-10-10 8:20:52";//开始时间
String end="2021-11-18 15:13:26";//结束时间
//yyyy-MM-dd HH:mm:ss 是你给的时间的格式，可以根据自己的需要进行修改，中间的连接符也是你所给时间的连接符(这里很容易出错)。
//注意：HH是24小时制，hh是12小时制。
SimpleDateFormat simpleDateFormat=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
//使用simpleDateFormat将时间格式化，并用Date封装时间
try {
Date startDate=simpleDateFormat.parse(start);
Date endDate=simpleDateFormat.parse(end);
//使用getTime方法获取两个时间的毫秒数
long start1= startDate.getTime();
long end1= endDate.getTime();
//秒数差
long sec=(end1-start1)/1000;
System.out.println("相差"+sec+"秒");
//分钟差
long minute=(end1-start1)/1000/60;
System.out.println("相差"+minute+"分");
//小时差
long hour=(end1-start1)/1000/60/60;
System.out.println("相差"+hour+"小时");
//天数差
long day=(end1-start1)/1000/60/60/24;
System.out.println("相差"+day+"天");
} catch (ParseException e) {
e.printStackTrace();
}
}
}
运行结果如下：
相差3394354秒 相差56572分 相差942小时 相差39天
注意：要用long类型的变量接收时间，不然会出现负数；
import java.text.SimpleDateFormat;
import java.util.Date;
public class DateDifferentExample {
public static void main(String[] args) {
String dateStart = "2013-02-19 09:29:58";
String dateStop = "2013-02-20 11:31:48";
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date d1 = null;
Date d2 = null;
try {
d1 = format.parse(dateStart);
d2 = format.parse(dateStop);
//毫秒ms
long diff = d2.getTime() - d1.getTime();
long diffSeconds = diff / 1000 % 60;
long diffMinutes = diff / (60 * 1000) % 60;
long diffHours = diff / (60 * 60 * 1000) % 24;
long diffDays = diff / (24 * 60 * 60 * 1000);
System.out.print("两个时间相差：");
System.out.print(diffDays + " 天, ");
System.out.print(diffHours + " 小时, ");
System.out.print(diffMinutes + " 分钟, ");
System.out.print(diffSeconds + " 秒.");
} catch (Exception e) {
e.printStackTrace();
}
}
使用Joda时间库计算时间差
import java.text.SimpleDateFormat;
import java.util.Date;
import org.joda.time.DateTime;
import org.joda.time.Days;
import org.joda.time.Hours;
import org.joda.time.Minutes;
import org.joda.time.Seconds;
public class JodaDateDifferentExample {
public static void main(String[] args) {
String dateStart = "2013-02-19 09:29:58";
String dateStop = "2013-02-20 11:31:48";
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date d1 = null;
Date d2 = null;
try {
d1 = format.parse(dateStart);
d2 = format.parse(dateStop);
DateTime dt1 = new DateTime(d1);
DateTime dt2 = new DateTime(d2);
System.out.print("两个时间相差：");
System.out.print(Days.daysBetween(dt1, dt2).getDays() + " 天, ");
System.out.print(Hours.hoursBetween(dt1, dt2).getHours() % 24
+ " 小时, ");
System.out.print(Minutes.minutesBetween(dt1, dt2).getMinutes() % 60
+ " 分钟, ");
System.out.print(Seconds.secondsBetween(dt1, dt2).getSeconds() % 60
+ " 秒.");
} catch (Exception e) {
e.printStackTrace();
}
}
}
运行结果：
两个时间相差：1 天, 2 小时, 1 分钟, 50 秒.
