Redis超详细分析分布式锁

<dependency>
<groupId>redis.clients</groupId>
<artifactId>jedis</artifactId>
<version>2.9.0</version>
</dependency>

public class RedisClientUtil {
//protected static Logger logger = Logger.getLogger(RedisUtil.class);
private static String IP = “www.kaicostudy.com”;
//Redis的端口号
private static int PORT = 6379;
//可用连接实例的最大数目，默认值为8；
//如果赋值为-1，则表示不限制；如果pool已经分配了maxActive个jedis实例，则此时pool的状态为exhausted(耗尽)。
private static int MAX_ACTIVE = 100;
//控制一个pool最多有多少个状态为idle(空闲的)的jedis实例，默认值也是8。
private static int MAX_IDLE = 20;
//等待可用连接的最大时间，单位毫秒，默认值为-1，表示永不超时。如果超过等待时间，则直接抛出JedisConnectionException；
private static int MAX_WAIT = 3000;
private static int TIMEOUT = 3000;
//在borrow一个jedis实例时，是否提前进行validate操作；如果为true，则得到的jedis实例均是可用的；
private static boolean TEST_ON_BORROW = true;
//在return给pool时，是否提前进行validate操作；
private static boolean TEST_ON_RETURN = true;
private static JedisPool jedisPool = null;
/**
* redis过期时间,以秒为单位
*/
public final static int EXRP_HOUR = 60 * 60; //一小时
public final static int EXRP_DAY = 60 * 60 * 24; //一天
public final static int EXRP_MONTH = 60 * 60 * 24 * 30; //一个月
/**
* 初始化Redis连接池
*/
private static void initialPool() {
try {
JedisPoolConfig config = new JedisPoolConfig();
config.setMaxTotal(MAX_ACTIVE);
config.setMaxIdle(MAX_IDLE);
config.setMaxWaitMillis(MAX_WAIT);
config.setTestOnBorrow(TEST_ON_BORROW);
jedisPool = new JedisPool(config, IP, PORT, TIMEOUT, “123456”);
} catch (Exception e) {
//logger.error(“First create JedisPool error : “+e);
e.getMessage();
}
}
/**
* 在多线程环境同步初始化
*/
private static synchronized void poolInit() {
if (jedisPool == null) {
initialPool();
}
}
/**
* 同步获取Jedis实例
*
* @return Jedis
*/
public synchronized static Jedis getJedis() {
if (jedisPool == null) {
poolInit();
}
Jedis jedis = null;
try {
if (jedisPool != null) {
jedis = jedisPool.getResource();
}
} catch (Exception e) {
e.getMessage();
// logger.error(“Get jedis error : “+e);
}
return jedis;
}
/**
* 释放jedis资源
*
* @param jedis
*/
public static void returnResource(final Jedis jedis) {
if (jedis != null && jedisPool != null) {
jedisPool.returnResource(jedis);
}
}
public static Long sadd(String key, String… members) {
Jedis jedis = null;
Long res = null;
try {
jedis = getJedis();
res = jedis.sadd(key, members);
} catch (Exception e) {
//logger.error(“sadd error : “+e);
e.getMessage();
}
return res;
}
}

public class RedisLock {
private static final int setnxSuccss = 1;
/**
* 获取锁
*
* @param lockKey 定义锁的key
* @param notLockTimeOut 没有获取锁的超时时间
* @param lockTimeOut 使用锁的超时时间
* @return
*/
public String getLock(String lockKey, int notLockTimeOut, int lockTimeOut) {
// 获取Redis连接
Jedis jedis = RedisClientUtil.getJedis();
// 定义没有获取锁的超时时间
Long endTimeOut = System.currentTimeMillis() + notLockTimeOut;
while (System.currentTimeMillis() < endTimeOut) {
String lockValue = UUID.randomUUID().toString();
// 如果在多线程情况下谁能够setnx 成功返回0 谁就获取到锁
if (jedis.setnx(lockKey, lockValue) == setnxSuccss) {
jedis.expire(lockKey, lockTimeOut / 1000);
return lockValue;
}
// 否则情况下 在超时时间内继续循环
}
try {
if (jedis != null) {
jedis.close();
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
/**
* 释放锁 其实就是将该key删除
*
* @return
*/
public Boolean unLock(String lockKey, String lockValue) {
Jedis jedis = RedisClientUtil.getJedis();
// 确定是对应的锁 ，才删除
if (lockValue.equals(jedis.get(lockKey))) {
return jedis.del(lockKey) > 0 ? true : false;
}
return false;
}
}

private RedisLock redisLock = new RedisLock();
private String lockKey = “kaico_lock”;
/**
* 测试Jedis实现分布式锁
* @return
*/
@GetMapping(“/restLock1”)
public String restLock1(){
// 1.获取锁
String lockValue = redisLock.getLock(lockKey, 5000, 5000);
if (StringUtils.isEmpty(lockValue)) {
System.out.println(Thread.currentThread().getName() + “,获取锁失败!”);
return “获取锁失败”;
}
// 2.获取锁成功执行业务逻辑
System.out.println(Thread.currentThread().getName() + “,获取成功，lockValue：” + lockValue);
// 3.释放lock锁
redisLock.unLock(lockKey, lockValue);
return “”;
}

@Component
public class SpringbootRedisLockUtil {
@Autowired
public RedisTemplate redisTemplate;
// 解锁原子性操作脚本
public static final String unlockScript=”if redis.call(\”get\”,KEYS[1]) == ARGV[1]\n”
+ “then\n”
+ ” return redis.call(\”del\”,KEYS[1])\n”
+ “else\n”
+ ” return 0\n”
+ “end”;
/**
* 加锁，有阻塞
* @param name
* @param expire
* @param timeout
* @return
*/
public String lock(String name, long expire, long timeout) throws UnsupportedEncodingException {
long startTime=System.currentTimeMillis();
String token;
do{
token=tryLock(name,expire);
if(token==null){
//设置等待时间，若等待时间过长则获取锁失败
if((System.currentTimeMillis()-startTime)>(timeout-50)){
break;
}
try {
Thread.sleep(50);//try it again per 50
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}while (token==null);
return token;
}
/**
* 解锁
* @param name
* @param token
* @return
*/
public Boolean unlock(String name, String token) throws UnsupportedEncodingException {
byte[][] keyArgs=new byte[2][];
keyArgs[0]= name.getBytes(Charset.forName(“UTF-8”));
keyArgs[1]= token.getBytes(Charset.forName(“UTF-8”));
RedisConnectionFactory connectionFactory = redisTemplate.getConnectionFactory();
RedisConnection connection = connectionFactory.getConnection();
try{
Long result = connection.scriptingCommands().eval(unlockScript.getBytes(Charset.forName(“UTF-8”)), ReturnType.INTEGER, 1, keyArgs);
if(result!=null&&result>0){
return true;
}

}finally {
RedisConnectionUtils.releaseConnection(connection,connectionFactory);
}
return false;
}
/**
* 加锁，无阻塞
* @param name
* @param expire
* @return
*/
public String tryLock(String name, long expire) throws UnsupportedEncodingException {
String token= UUID.randomUUID().toString();
RedisConnectionFactory connectionFactory = redisTemplate.getConnectionFactory();
RedisConnection connection = connectionFactory.getConnection();
try{
Boolean result = connection.set(name.getBytes(Charset.forName(“UTF-8”)), token.getBytes(Charset.forName(“UTF-8”)),
Expiration.from(expire, TimeUnit.MILLISECONDS), RedisStringCommands.SetOption.SET_IF_ABSENT);
if(result!=null&&result){
return token;
}
}
finally {
RedisConnectionUtils.releaseConnection(connection,connectionFactory);
}
return null;
}
}

@Autowired
private SpringbootRedisLockUtil springbootRedisLockUtil;
@PostMapping(“/restLock1”)
public void restLock2() throws UnsupportedEncodingException {
String token;
token=springbootRedisLockUtil.lock(Thread.currentThread().getName(),1000,11000);
if(token!=null){
System.out.println(“我拿到锁了哦!”);
}
else{
System.out.println(“我没有拿到锁！”);
}
springbootRedisLockUtil.unlock(Thread.currentThread().getName(),token);
}