使用redis生成唯一编号及原理示例详解

<dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.1</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
            <version>${spring.boot.version}</version>
        </dependency>

server.port=9091
server.servlet.context-path=/

spring.redis.host=127.0.0.1
spring.redis.port=6379
#spring.redis.password=1234
spring.redis.database=0

package com.xiaochun.service;

import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.support.atomic.RedisAtomicLong;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

@Service
public class SequenceService {

    private static Logger logger = LoggerFactory.getLogger(SequenceService.class);

    @Resource
    private RedisTemplate redisTemplate;

    //用作存放redis中的key
    private static String ORDER_KEY = "order_key";
    
    //生成特定的业务编号，prefix为特定的业务代码
    public String getOrderNo(String prefix){
         return getSeqNo(ORDER_KEY, prefix);
    }
    
    //SequenceService类中公用部分，传入制定的key和prefix
    private String getSeqNo(String key, String prefix)
    {
        Calendar calendar = Calendar.getInstance();
        calendar.set(Calendar.HOUR_OF_DAY, 23);
        calendar.set(Calendar.MINUTE, 59);
        calendar.set(Calendar.SECOND, 59);
        calendar.set(Calendar.MILLISECOND, 999);
        //设置过期时间，这里设置为当天的23:59:59
        Date expireDate = calendar.getTime();
        //返回当前redis中的key的最大值
        Long seq = generate(redisTemplate, key, expireDate);
        //获取当天的日期，格式为yyyyMMdd
        String date = new SimpleDateFormat("yyyyMMdd").format(expireDate);
        //生成八为的序列号，如果seq不够八位，seq前面补0，
        //如果seq位数超过了八位，那么无需补0直接返回当前的seq
        String sequence = StringUtils.leftPad(seq.toString(), 8, "0");
        if (prefix == null)
        {
            prefix = "";
        }
        //拼接业务编号
        String seqNo = prefix + date + sequence;
        logger.info("KEY:{}, 序列号生成:{}, 过期时间:{}", key, seqNo, String.format("%tF %tT ", expireDate, expireDate));
        return seqNo;
    }

    /**
     * @param key
     * @param expireTime <i>过期时间</i>
     * @return
     */
    public static long generate(RedisTemplate<?,?> redisTemplate,String key,Date expireTime) {
        //RedisAtomicLong为原子类，根据传入的key和redis链接工厂创建原子类
        RedisAtomicLong counter = new RedisAtomicLong(key,redisTemplate.getConnectionFactory());
        //设置过期时间
        counter.expireAt(expireTime);
        //返回redis中key的值，内部实现下面详细说明
        return counter.incrementAndGet();
    }

}

public class RedisAtomicLong extends Number implements Serializable, BoundKeyOperations<String> {
    private static final long serialVersionUID = 1L;
    //redis中的key，用volatile修饰，获得原子性
    private volatile String key;
    //当前的key-value对象，根据传入的key获取value值
    private ValueOperations<String, Long> operations;
    //传入当前redisTemplate对象，为RedisTemplate对象的顶级接口
    private RedisOperations<String, Long> generalOps;

    public RedisAtomicLong(String redisCounter, RedisConnectionFactory factory) {
        this(redisCounter, (RedisConnectionFactory)factory, (Long)null);
    }
    private RedisAtomicLong(String redisCounter, RedisConnectionFactory factory, Long initialValue) {
        Assert.hasText(redisCounter, "a valid counter name is required");
        Assert.notNull(factory, "a valid factory is required");
        //初始化一个RedisTemplate对象
        RedisTemplate<String, Long> redisTemplate = new RedisTemplate();
        redisTemplate.setKeySerializer(new StringRedisSerializer());
        redisTemplate.setValueSerializer(new GenericToStringSerializer(Long.class));
        redisTemplate.setExposeConnection(true);
        //设置当前的redis连接工厂
        redisTemplate.setConnectionFactory(factory);
        redisTemplate.afterPropertiesSet();
        //设置传入的key
        this.key = redisCounter;
        //设置当前的redisTemplate
        this.generalOps = redisTemplate;
        //获取当前的key-value集合
        this.operations = this.generalOps.opsForValue();
        //设置默认值，如果传入为null，则key获取operations中的value，如果value为空，设置默认值为0
        if (initialValue == null) {
            if (this.operations.get(redisCounter) == null) {
                this.set(0L);
            }
        //不为空则设置为传入的值
        } else {
            this.set(initialValue);
        }
    }
    //将传入key的value+1并返回
    public long incrementAndGet() {
        return this.operations.increment(this.key, 1L);
    }