Lock.java

import java.util.UUID;
import java.util.concurrent.TimeUnit;

/**
 * Created by huangxx on 2017/6/27.
 */
@Service
@Log4j2
public class LockKeyService {

    @Autowired
    private RedisTemplate<String, String> redisTemplate;

    private static final String LOCK_NAME = "LOCK_NAMKE:%s";

    @Override
    public String getKeyByrequestId(String requestId) {
        String identifier = acquireLockAndWait(requestId, 2, 5);
        if (StringUtils.isNotBlank(identifier)) {
            try {
                secretKey = generateKey(requestId);
                dosomething(secretKey);
            } catch (Exception e) {
               ......
            } finally {
                releaseLock(requestId, identifier);
            }
        }
        return secretKey;
    }

    /**
     * @param requestId
     * @param acquireLockTimeout 获取锁超时时间 单位：s
     * @param lockTimeout        锁过期时间 单位：s
     * @return
     */
    private String acquireLockWithTimeout(String requestId, long acquireLockTimeout, long lockTimeout) {
        String identifier = UUID.randomUUID().toString();
        String lockName = String.format(LOCK_NAME, requestId);
        long end = System.currentTimeMillis() + acquireLockTimeout * 1000;
        while (System.currentTimeMillis() < end) {
            if (redisTemplate.opsForValue().setIfAbsent(lockName, identifier)) {
                expire(lockName, lockTimeout, TimeUnit.SECONDS);
                return identifier;
            }
            if (redisTemplate.getExpire(lockName) == -1) {
                expire(lockName, lockTimeout, TimeUnit.SECONDS);
            }
            try {
                Thread.sleep(500);
            } catch (InterruptedException ie) {
                log.error("acquireLockWithTimeout thread sleep error!", ie);
            }
        }
        return null;
    }

    /**
     * @param requestId
     * @param waitTime    等待时间 单位：s
     * @param lockTimeout 锁过期时间 单位：s
     * @return
     */
    private String acquireLockAndWait(String requestId, long waitTime, long lockTimeout) {
        String identifier = UUID.randomUUID().toString();
        String lockName = String.format(LOCK_NAME, requestId);
        if (redisTemplate.opsForValue().setIfAbsent(lockName, identifier)) {
            expire(lockName, lockTimeout, TimeUnit.SECONDS);
            return identifier;
        }
        if (redisTemplate.getExpire(lockName) == -1) {
            expire(lockName, lockTimeout, TimeUnit.SECONDS);
        }
        try {
            Thread.sleep(waitTime * 1000);
        } catch (InterruptedException ie) {
            log.error("acquireLockAndWait thread sleep error!", ie);
        }
        return null;
    }

    /**
     * 释放锁，只有锁内容符合时才会释放
     *
     * @param requestId     用户id
     * @param identifier 锁内容
     * @return
     */
    private boolean releaseLock(String requestId, String identifier) {
        String lockName = String.format(LOCK_NAME, requestId);
        while (true) {
            if (identifier.equals(redisTemplate.opsForValue().get(lockName))) {
                redisTemplate.delete(lockName);
                return true;
            }
            break;
        }
        return false;
    }

    private String dosomething(String requestId) {
        ......
    }

    private void expire(String key, long time, TimeUnit timeUnit) {
        boolean success = redisTemplate.expire(key, time, timeUnit);
        while(!success){
            success = redisTemplate.expire(key, time, timeUnit);
        }
    }

}