Use redis to realize self increment serial number

Use Redis Realize self increment serial number

Scenario requirements

There is a scenario in the project that a serial number needs to be generated after the guest meal application is approved , The rule is ：202202150001,202202150002,qian' How many are month, year and day , The last four digits increase in turn .

The thought of Redis It's memory based , And it's fast , It also does not occupy database resources . Therefore, it is adopted Redis How to achieve .

Code implementation

Form rule tool class ：

/**
 * @author Greenarrow
 * @date 2022-02-15 8:01
 **/
public class SequenceUtil {

    static final int DEFAULT_LENGTH = 4;

    /**
     *  format  key 
     * @param seq
     * @return
     */
    public static String getSequence(Long seq) {
        String str = String.valueOf(seq);
        int len = str.length();
        //  Depending on the size of the business 
        if (len >= DEFAULT_LENGTH) {
            return str;
        }
        int rest = DEFAULT_LENGTH - len;
        StringJoiner stringJoiner = new StringJoiner("");
        for (int i = 0; i < rest; i++) {
            stringJoiner.add("0");
        }
        stringJoiner.add(str);
        return stringJoiner.toString();
    }

    /**
     *  Get the current date 
     * @return
     */
    public static String getCurrentDate(){
        LocalDate localDate = LocalDate.now();
        DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyyMMdd");
        return df.format(localDate);
    }
}

Get increment ：

  /**
     *  Get increment 
     * @param key
     * @return
     */
    public long incr(String key){
        return stringRedisTemplate.opsForValue().increment(key);
    }

Concrete realization ：

        String currentDate = SequenceUtil.getCurrentDate();
        String key = "serial.number:" + currentDate;
        long sequence = redisService.incr(key);
        String seq = SequenceUtil.getSequence(sequence);
        StringJoiner sj = new StringJoiner("");
        sj.add(currentDate).add(seq);
        System.out.println(sj.toString());

Output results ：

202202150001
202202150002
202202150003
202202150004

Local Redis Data in the library ：

Expanding knowledge

Redis There are two strategies for serialization , Namely StringRedisTemplate and RedisTemplate, among StringRedisTemplate String for operation ,RedisTemplate It uses JDK Default binary serialization .

Everybody knows redis Serialization is to change key,value The value is first converted to the form of a stream , Store it in redis in .

RedisTemplate It is used. JdkSerializationRedisSerializer serialize , The serialized value contains object information , Version number , Class information, etc , It's a string , Therefore, it is impossible to increase the value by itself .

and StringRedisTemplate The serialization strategy is to convert the value of a string directly into a byte array , So store it in redis In is the value , Therefore, self increment operation can be carried out .

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