使用场景
用户登录后,需要把用户信息(一般是session)保存到redis中并设置过期时间
1.pom文件中引入springboot-redis依赖
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>
2.application.properties中加入redis数据库连接信息
#redis 配置
# Redis数据库索引(默认为0)
spring.redis.database=0
# Redis服务器地址
spring.redis.host=127.0.0.1
# Redis服务器连接端口
spring.redis.port=6379
3.controller中注入雪花算法实例和redisTemplate实例
@Resource
private SnowFlake snowFlake;
@Resource
private RedisTemplate redisTemplate;
4.controller中使用雪花算法生成token并放入redis中并打印token日志信息
@PostMapping("/login")
public CommonResp login(@Valid @RequestBody UserLoginReq req) {
req.setPassword(DigestUtils.md5DigestAsHex(req.getPassword().getBytes()));
CommonResp<UserLoginResp> resp = new CommonResp<>();
UserLoginResp userLoginResp = userService.login(req);
String token = snowFlake.nextId()+"";
LOG.info("生成单点登录token:{},并放入redis中", token);
userLoginResp.setToken(token);
redisTemplate.opsForValue().set(token, JSONObject.toJSONString(userLoginResp), 3600 * 24, TimeUnit.SECONDS);
resp.setContent(userLoginResp);
return resp;
}
关于redis的注意事项:
雪花算法
1.添加utils包下的SnowFlake文件
package com.futureport.wiki.utils;
import org.springframework.stereotype.Component;
import java.text.ParseException;
/**
* Twitter的分布式自增ID雪花算法
**/
@Component
public class SnowFlake {
/**
* 起始的时间戳
*/
private final static long START_STMP = 1609459200000L; // 2021-01-01 00:00:00
/**
* 每一部分占用的位数
*/
private final static long SEQUENCE_BIT = 7; //序列号占用的位数
private final static long MACHINE_BIT = 5; //机器标识占用的位数
private final static long DATACENTER_BIT = 5;//数据中心占用的位数
/**
* 每一部分的最大值
*/
private final static long MAX_DATACENTER_NUM = -1L ^ (-1L << DATACENTER_BIT);
private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);
/**
* 每一部分向左的位移
*/
private final static long MACHINE_LEFT = SEQUENCE_BIT;
private final static long DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
private final static long TIMESTMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;
private long datacenterId = 1; //数据中心
private long machineId = 1; //机器标识
private long sequence = 0L; //序列号
private long lastStmp = -1L;//上一次时间戳
public SnowFlake() {
}
public SnowFlake(long datacenterId, long machineId) {
if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {
throw new IllegalArgumentException("datacenterId can't be greater than MAX_DATACENTER_NUM or less than 0");
}
if (machineId > MAX_MACHINE_NUM || machineId < 0) {
throw new IllegalArgumentException("machineId can't be greater than MAX_MACHINE_NUM or less than 0");
}
this.datacenterId = datacenterId;
this.machineId = machineId;
}
/**
* 产生下一个ID
*
* @return
*/
public synchronized long nextId() {
long currStmp = getNewstmp();
if (currStmp < lastStmp) {
throw new RuntimeException("Clock moved backwards. Refusing to generate id");
}
if (currStmp == lastStmp) {
//相同毫秒内,序列号自增
sequence = (sequence + 1) & MAX_SEQUENCE;
//同一毫秒的序列数已经达到最大
if (sequence == 0L) {
currStmp = getNextMill();
}
} else {
//不同毫秒内,序列号置为0
sequence = 0L;
}
lastStmp = currStmp;
return (currStmp - START_STMP) << TIMESTMP_LEFT //时间戳部分
| datacenterId << DATACENTER_LEFT //数据中心部分
| machineId << MACHINE_LEFT //机器标识部分
| sequence; //序列号部分
}
private long getNextMill() {
long mill = getNewstmp();
while (mill <= lastStmp) {
mill = getNewstmp();
}
return mill;
}
private long getNewstmp() {
return System.currentTimeMillis();
}
public static void main(String[] args) throws ParseException {
// 时间戳
// System.out.println(System.currentTimeMillis());
// System.out.println(new Date().getTime());
//
// String dateTime = "2021-01-01 08:00:00";
// SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
// System.out.println(sdf.parse(dateTime).getTime());
SnowFlake snowFlake = new SnowFlake(1, 1);
long start = System.currentTimeMillis();
for (int i = 0; i < 10; i++) {
System.out.println(snowFlake.nextId());
System.out.println(System.currentTimeMillis() - start);
}
}
}