redis锁

redis锁 博客地址：http://www.importnew.com/27477.html 。
DistributedLock

package com.timer.common.redis;
public interface DistributedLock {
	public static final long TIMEOUT_MILLIS = 10000;

	public static final int RETRY_TIMES = Integer.MAX_VALUE;

	public static final long SLEEP_MILLIS = 500;

	public boolean lock(String key);

	public boolean lock(String key, int retryTimes);

	public boolean lock(String key, int retryTimes, long sleepMillis);

	public boolean lock(String key, long expire);

	public boolean lock(String key, long expire, int retryTimes);

	public boolean lock(String key, long expire, int retryTimes, long sleepMillis);

	public boolean releaseLock(String key);
}

AbstractDistributedLock

package com.timer.common.redis;

public abstract class AbstractDistributedLock implements DistributedLock {

	@Override
	public boolean lock(String key) {
		return lock(key, TIMEOUT_MILLIS, RETRY_TIMES, SLEEP_MILLIS);
	}

	@Override
	public boolean lock(String key, int retryTimes) {
		return lock(key, TIMEOUT_MILLIS, retryTimes, SLEEP_MILLIS);
	}

	@Override
	public boolean lock(String key, int retryTimes, long sleepMillis) {
		return lock(key, TIMEOUT_MILLIS, retryTimes, sleepMillis);
	}

	@Override
	public boolean lock(String key, long expire) {
		return lock(key, expire, RETRY_TIMES, SLEEP_MILLIS);
	}

	@Override
	public boolean lock(String key, long expire, int retryTimes) {
		return lock(key, expire, retryTimes, SLEEP_MILLIS);
	}

}

RedisDistributedLock
package com.timer.common.redis;

import java.util.ArrayList;
import java.util.List;
import java.util.UUID;

import javax.annotation.Resource;

import org.apache.commons.lang3.StringUtils;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.dao.DataAccessException;
import org.springframework.data.redis.connection.RedisConnection;
import org.springframework.data.redis.core.RedisCallback;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.stereotype.Component;

import lombok.extern.slf4j.Slf4j;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisCommands;

@Slf4j
@Component
public class RedisDistributedLock extends AbstractDistributedLock {
    @Resource
    private RedisTemplate redisTemplate;

    private ThreadLocal lockFlag = new ThreadLocal();

    public static final String UNLOCK_LUA;

    static {
        StringBuilder sb = new StringBuilder();
        sb.append("if redis.call(\"get\",KEYS[1]) == ARGV[1] ");
        sb.append("then ");
        sb.append("    return redis.call(\"del\",KEYS[1]) ");
        sb.append("else ");
        sb.append("    return 0 ");
        sb.append("end ");
        UNLOCK_LUA = sb.toString();
    }

    public RedisDistributedLock(RedisTemplate redisTemplate) {
        super();
        this.redisTemplate = redisTemplate;
    }

    @Override
    public boolean lock(String key, long expire, int retryTimes, long sleepMillis) {
        boolean result = setRedis(key, expire);
        // 如果获取锁失败，按照传入的重试次数进行重试
        while ((!result) && retryTimes-- > 0) {
            try {
                log.debug("lock failed, retrying..." + retryTimes);
                Thread.sleep(sleepMillis);
            } catch (InterruptedException e) {
                return false;
            }
            result = setRedis(key, expire);
        }
        return result;
    }

    private boolean setRedis(String key, long expire) {
        try {
            String result = redisTemplate.execute(new RedisCallback() {
                @Override
                public String doInRedis(RedisConnection connection) throws DataAccessException {
                    JedisCommands commands = (JedisCommands) connection.getNativeConnection();
                    String uuid = UUID.randomUUID().toString();
                    lockFlag.set(uuid);
                    return commands.set(key, uuid, "NX", "PX", expire);
                }
            });
            return !StringUtils.isEmpty(result);
        } catch (Exception e) {
            log.error("set redis occured an exception", e);
        }
        return false;
    }

    @Override
    public boolean releaseLock(String key) {
        // 释放锁的时候，有可能因为持锁之后方法执行时间大于锁的有效期，此时有可能已经被另外一个线程持有锁，所以不能直接删除
        try {
            List keys = new ArrayList();
            keys.add(key);
            List args = new ArrayList();
            args.add(lockFlag.get());

            // 使用lua脚本删除redis中匹配value的key，可以避免由于方法执行时间过长而redis锁自动过期失效的时候误删其他线程的锁
            // spring自带的执行脚本方法中，集群模式直接抛出不支持执行脚本的异常，所以只能拿到原redis的connection来执行脚本

            Long result = redisTemplate.execute(new RedisCallback() {
                public Long doInRedis(RedisConnection connection) throws DataAccessException {
                    Object nativeConnection = connection.getNativeConnection();
                    // 集群模式和单机模式虽然执行脚本的方法一样，但是没有共同的接口，所以只能分开执行
                    // 集群模式
//                    if (nativeConnection instanceof JedisCluster) {
//                        return (Long) ((JedisCluster) nativeConnection).eval(UNLOCK_LUA, keys, args);
//                    }

                    // 单机模式
//                    else 
                    if (nativeConnection instanceof Jedis) {
                        return (Long) ((Jedis) nativeConnection).eval(UNLOCK_LUA, keys, args);
                    }
                    return 0L;
                }
            });

            return result != null && result > 0;
        } catch (Exception e) {
            log.error("release lock occured an exception", e);
        }
        return false;
    }

}

例子

	if (distributedLock.lock("do_approval_" + approvalUuid, 5 * 1000l, 1)) {
	            try {
	                approvalDoReturnVo = approvalService.doApprovalNewVersion(approvalUuid, approverReason, action);
	                distributedLock.releaseLock("do_approval_" + approvalUuid);
	            } catch (Exception e) {
	                distributedLock.releaseLock("do_approval_" + approvalUuid);
	                throw e;
	            }
	        }