扩展redisTemplate实现分布式锁
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原文:https://blog.csdn.net/qq1010267837/article/details/79697572
依赖jar包
compile group: ‘redis.clients‘, name: ‘jedis‘, version:‘2.8.1‘
compile group: ‘org.springframework.data‘, name: ‘spring-data-redis‘, version:‘1.6.5.RELEASE‘
/** * Redis的分布式锁对象 * Created by zhengjy on 2017/3/6. */ public interface RedisLock extends AutoCloseable { /** * 释放分布式锁 */ void unlock(); }
import org.slf4j.Logger; import org.slf4j.LoggerFactory; 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.data.redis.core.StringRedisTemplate; import org.springframework.data.redis.core.script.DefaultRedisScript; import redis.clients.jedis.Jedis; import java.util.ArrayList; import java.util.Collections; import java.util.List; import java.util.concurrent.TimeUnit; /** * @Resource(name="stringRedisTemplate") * private RedisAtomicClient redisAtomicClient; * * 提供Redis一些不直接支持的原子性的操作,很多实现采用了lua脚本 * Created by zhengjy on 2017/3/6. */ public class RedisAtomicClient { private static final Logger logger = LoggerFactory.getLogger(RedisAtomicClient.class); private final RedisTemplate redisTemplate; private final StringRedisTemplate stringRedisTemplate; private static final String INCR_BY_WITH_TIMEOUT = "local v;" + " v = redis.call(‘incrBy‘,KEYS[1],ARGV[1]);" + "if tonumber(v) == 1 then " + " redis.call(‘expire‘,KEYS[1],ARGV[2]) " + "end " + "return v"; private static final String COMPARE_AND_DELETE = "if redis.call(‘get‘,KEYS[1]) == ARGV[1] " + "then " + " return redis.call(‘del‘,KEYS[1]) " + "else " + " return 0 " + "end"; public RedisAtomicClient(RedisTemplate redisTemplate){ this.redisTemplate = redisTemplate; this.stringRedisTemplate = new StringRedisTemplate(); this.stringRedisTemplate.setConnectionFactory(redisTemplate.getConnectionFactory()); this.stringRedisTemplate.afterPropertiesSet(); } /** * 根据key获得对应的long类型数值,不存在则返回null(本方法使用string序列化方式) * @param key * @return */ public Long getLong(String key){ try { String val = stringRedisTemplate.opsForValue().get(key); if(val == null){ return null; }else{ return Long.valueOf(val); } } catch(Exception e){ logger.error("get key error:"+key, e); return null; } } /** * 计数器,支持设置失效时间,如果key不存在,则调用此方法后计数器为1(本方法使用string序列化方式) * @param key * @param delta 可以为负数 * @param timeout 缓存失效时间 * @param timeUnit 缓存失效时间的单位 * @return */ public Long incrBy(String key, long delta, long timeout, TimeUnit timeUnit){ List<String> keys = new ArrayList<>(); keys.add(key); long timeoutSeconds = TimeUnit.SECONDS.convert(timeout, timeUnit); String[] args = new String[2]; args[0] = String.valueOf(delta); args[1] = String.valueOf(timeoutSeconds); Object currentVal = stringRedisTemplate.execute(new DefaultRedisScript<>(INCR_BY_WITH_TIMEOUT, String.class), keys, args); if(currentVal instanceof Long){ return (Long)currentVal; } return Long.valueOf((String)currentVal); } /** * 获取redis的分布式锁,内部实现使用了redis的setnx。只会尝试一次,如果锁定失败返回null,如果锁定成功则返回RedisLock对象,调用方需要调用RedisLock.unlock()方法来释放锁. * <br/>使用方法: * <pre> * RedisLock lock = redisAtomicClient.getLock(key, 2); * if(lock != null){ * try { * //lock succeed, do something * }finally { * lock.unlock(); * } * } * </pre> * 由于RedisLock实现了AutoCloseable,所以可以使用更简介的使用方法: * <pre> * try(RedisLock lock = redisAtomicClient.getLock(key, 2)) { * if (lock != null) { * //lock succeed, do something * } * } * </pre> * @param key 要锁定的key * @param expireSeconds key的失效时间 * @return 获得的锁对象(如果为null表示获取锁失败),后续可以调用该对象的unlock方法来释放锁. */ public RedisLock getLock(final String key, long expireSeconds){ return getLock(key, expireSeconds, 0, 0); } /** * 获取redis的分布式锁,内部实现使用了redis的setnx。如果锁定失败返回null,如果锁定成功则返回RedisLock对象,调用方需要调用RedisLock.unlock()方法来释放锁 * <br/> * <span style="color:red;">此方法在获取失败时会自动重试指定的次数,由于多次等待会阻塞当前线程,请尽量避免使用此方法</span> * * @param key 要锁定的key * @param expireSeconds key的失效时间 * @param maxRetryTimes 最大重试次数,如果获取锁失败,会自动尝试重新获取锁; * @param retryIntervalTimeMillis 每次重试之前sleep等待的毫秒数 * @return 获得的锁对象(如果为null表示获取锁失败),后续可以调用该对象的unlock方法来释放锁. */ public RedisLock getLock(final String key, final long expireSeconds, int maxRetryTimes, long retryIntervalTimeMillis){ final String value = key.hashCode()+""; int maxTimes = maxRetryTimes + 1; for(int i = 0;i < maxTimes; i++) { String status = stringRedisTemplate.execute(new RedisCallback<String>() { @Override public String doInRedis(RedisConnection connection) throws DataAccessException { Jedis jedis = (Jedis) connection.getNativeConnection(); String status = jedis.set(key, value, "nx", "ex", expireSeconds); return status; } }); if ("OK".equals(status)) {//抢到锁 return new RedisLockInner(stringRedisTemplate, key, value); } if(retryIntervalTimeMillis > 0) { try { Thread.sleep(retryIntervalTimeMillis); } catch (InterruptedException e) { break; } } if(Thread.currentThread().isInterrupted()){ break; } } return null; } private class RedisLockInner implements RedisLock{ private StringRedisTemplate stringRedisTemplate; private String key; private String expectedValue; protected RedisLockInner(StringRedisTemplate stringRedisTemplate, String key, String expectedValue){ this.stringRedisTemplate = stringRedisTemplate; this.key = key; this.expectedValue = expectedValue; } /** * 释放redis分布式锁 */ @Override public void unlock(){ List<String> keys = Collections.singletonList(key); stringRedisTemplate.execute(new DefaultRedisScript<>(COMPARE_AND_DELETE, String.class), keys, expectedValue); } @Override public void close() throws Exception { this.unlock(); } } }
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