基于redis的分布式自增序列

RedisAtomicInteger，RedisAtomicLong 是spring-data-redis.jar提供的方法，springboot加入redis模块自动引入

1. 这两个类与AtomicInteger的区别是，一个是分布式自增，一个是jvm内自增
2. int和long增到最大时会变成负数，处理方法是，检测到负数时设置为0，见下面代码
3. 性能，不加此调用，并发量360；加了此调用，并发量330，看出对性能影响很小

package com.example.demo.service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.support.atomic.RedisAtomicInteger;
import org.springframework.data.redis.support.atomic.RedisAtomicLong;
import org.springframework.stereotype.Service;

import javax.annotation.PostConstruct;

@Service
public class KeyGenertService {
     
    @Autowired
    RedisTemplate<String, String> redisTemplate;

    private RedisAtomicInteger counter_int_tx;
    private RedisAtomicLong counter_long_tx2;

    @PostConstruct
    public void init() {
     
        counter_int_tx = new RedisAtomicInteger("int_tx", redisTemplate.getConnectionFactory());
        counter_long_tx2 = new RedisAtomicLong("long_tx2", redisTemplate.getConnectionFactory());
    }
    
    public int generate_int_tx() {
     
        int i = counter_int_tx.incrementAndGet();
        if (i < 0) {
     
            synchronized (this) {
     
                i = counter_int_tx.incrementAndGet();
                if (i < 0) {
     
                    counter_int_tx.set(0);
                    i = 0;
                }
            }
        }
        return i;
    }

    public long generate_long_tx2() {
     
        long i = counter_long_tx2.incrementAndGet();
        if (i < 0) {
     
            synchronized (this) {
     
                i = counter_long_tx2.incrementAndGet();
                if (i < 0) {
     
                    counter_long_tx2.set(0);
                    i = 0;
                }
            }
        }
        return i;
    }
}