Redis分布式锁----悲观锁实现,以秒杀系统为例

摘要：本文要实现的是一种使用redis来实现分布式锁。

本文源码请在这里下载：https://github.com/appleappleapple/DistributeLearning

1、分布式锁

分布式锁在是一种用来安全访问分式式机器上变量的安全方案，一般用在全局id生成，秒杀系统，全局变量共享、分布式事务等。一般会有两种实现方案，一种是悲观锁的实现，一种是乐观锁的实现。悲观锁的并发性能差，但是能保证不会发生脏数据的可能性小一点。

2、Redis命令介绍
使用Redis实现分布式锁，有两个重要函数需要介绍

SETNX命令（SET if Not eXists）
语法：
SETNX key value
功能：
当且仅当 key 不存在，将 key 的值设为 value ，并返回1；若给定的 key 已经存在，则 SETNX 不做任何动作，并返回0。

GETSET命令（这是一个原子命令！）
语法：
GETSET key value
功能：
将给定 key 的值设为 value ，并返回 key 的旧值 (old value)，当 key 存在但不是字符串类型时，返回一个错误，当key不存在时，返回nil。

GET命令
语法：
GET key
功能：
返回 key 所关联的字符串值，如果 key 不存在那么返回特殊值 nil 。

DEL命令
语法：
DEL key [KEY …]
功能：
删除给定的一个或多个 key ,不存在的 key 会被忽略。

3、代码实现

（1）AbstractLock基类

package com.github.distribute.lock.redis;import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;/*** 锁的骨架实现, 真正的获取锁的步骤由子类去实现.* **/
public abstract class AbstractLock implements Lock {/*** <pre>* 这里需不需要保证可见性值得讨论, 因为是分布式的锁, * 1.同一个jvm的多个线程使用不同的锁对象其实也是可以的, 这种情况下不需要保证可见性 * 2.同一个jvm的多个线程使用同一个锁对象, 那可见性就必须要保证了.* </pre>*/protected volatile boolean locked;/*** 当前jvm内持有该锁的线程(if have one)*/private Thread exclusiveOwnerThread;public void lock() {try {lock(false, 0, null, false);} catch (InterruptedException e) {// TODO ignore}}public void lockInterruptibly() throws InterruptedException {lock(false, 0, null, true);}public boolean tryLock(long time, TimeUnit unit) {try {System.out.println("ghggggggggggggg");return lock(true, time, unit, false);} catch (InterruptedException e) {e.printStackTrace();System.out.println("" + e);}return false;}public boolean tryLockInterruptibly(long time, TimeUnit unit) throws InterruptedException {return lock(true, time, unit, true);}public void unlock() {// TODO 检查当前线程是否持有锁if (Thread.currentThread() != getExclusiveOwnerThread()) {throw new IllegalMonitorStateException("current thread does not hold the lock");}unlock0();setExclusiveOwnerThread(null);}protected void setExclusiveOwnerThread(Thread thread) {exclusiveOwnerThread = thread;}protected final Thread getExclusiveOwnerThread() {return exclusiveOwnerThread;}protected abstract void unlock0();/*** 阻塞式获取锁的实现* * @param useTimeout* @param time* @param unit* @param interrupt*            是否响应中断* @return* @throws InterruptedException*/protected abstract boolean lock(boolean useTimeout, long time, TimeUnit unit, boolean interrupt)throws InterruptedException;}

（2）、实现类

package com.github.distribute.lock.redis;import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;import redis.clients.jedis.Jedis;/*** 基于Redis的SETNX操作实现的分布式锁* * 获取锁时最好用lock(long time, TimeUnit unit), 以免网路问题而导致线程一直阻塞*/
public class RedisBasedDistributedLock extends AbstractLock {private Jedis jedis;// 锁的名字protected String lockKey;// 锁的有效时长(毫秒)protected long lockExpires;public RedisBasedDistributedLock(Jedis jedis, String lockKey, long lockExpires) {this.jedis = jedis;this.lockKey = lockKey;this.lockExpires = lockExpires;}// 阻塞式获取锁的实现protected boolean lock(boolean useTimeout, long time, TimeUnit unit, boolean interrupt) throws InterruptedException {System.out.println("test1");if (interrupt) {checkInterruption();}System.out.println("test2");long start = System.currentTimeMillis();long timeout = unit.toMillis(time); // if !useTimeout, then it's uselesswhile (useTimeout ? isTimeout(start, timeout) : true) {System.out.println("test3");if (interrupt) {checkInterruption();}long lockExpireTime = System.currentTimeMillis() + lockExpires + 1;// 锁超时时间String stringOfLockExpireTime = String.valueOf(lockExpireTime);System.out.println("test4");if (jedis.setnx(lockKey, stringOfLockExpireTime) == 1) { // 获取到锁System.out.println("test5");//成功获取到锁, 设置相关标识locked = true;setExclusiveOwnerThread(Thread.currentThread());return true;}System.out.println("test6");String value = jedis.get(lockKey);if (value != null && isTimeExpired(value)) { // lock is expiredSystem.out.println("test7");// 假设多个线程(非单jvm)同时走到这里String oldValue = jedis.getSet(lockKey, stringOfLockExpireTime); //原子操作// 但是走到这里时每个线程拿到的oldValue肯定不可能一样(因为getset是原子性的)// 加入拿到的oldValue依然是expired的，那么就说明拿到锁了System.out.println("test8");if (oldValue != null && isTimeExpired(oldValue)) {System.out.println("test9");//成功获取到锁, 设置相关标识locked = true;setExclusiveOwnerThread(Thread.currentThread());return true;}} else {// TODO lock is not expired, enter next loop retrying}}System.out.println("test10");return false;}public boolean tryLock() {long lockExpireTime = System.currentTimeMillis() + lockExpires + 1;// 锁超时时间String stringOfLockExpireTime = String.valueOf(lockExpireTime);if (jedis.setnx(lockKey, stringOfLockExpireTime) == 1) { // 获取到锁// 成功获取到锁, 设置相关标识locked = true;setExclusiveOwnerThread(Thread.currentThread());return true;}String value = jedis.get(lockKey);if (value != null && isTimeExpired(value)) { // lock is expired// 假设多个线程(非单jvm)同时走到这里String oldValue = jedis.getSet(lockKey, stringOfLockExpireTime); //原子操作// 但是走到这里时每个线程拿到的oldValue肯定不可能一样(因为getset是原子性的)// 假如拿到的oldValue依然是expired的，那么就说明拿到锁了if (oldValue != null && isTimeExpired(oldValue)) {//成功获取到锁, 设置相关标识locked = true;setExclusiveOwnerThread(Thread.currentThread());return true;}} else {// TODO lock is not expired, enter next loop retrying}return false;}/*** Queries if this lock is held by any thread.* * @return {@code true} if any thread holds this lock and {@code false}*         otherwise*/public boolean isLocked() {if (locked) {return true;} else {String value = jedis.get(lockKey);// TODO 这里其实是有问题的, 想:当get方法返回value后, 假设这个value已经是过期的了,// 而就在这瞬间, 另一个节点set了value, 这时锁是被别的线程(节点持有), 而接下来的判断// 是检测不出这种情况的.不过这个问题应该不会导致其它的问题出现, 因为这个方法的目的本来就// 不是同步控制, 它只是一种锁状态的报告.return !isTimeExpired(value);}}@Overrideprotected void unlock0() {// 判断锁是否过期String value = jedis.get(lockKey);if (!isTimeExpired(value)) {doUnlock();}}private void checkInterruption() throws InterruptedException {if (Thread.currentThread().isInterrupted()) {throw new InterruptedException();}}private boolean isTimeExpired(String value) {return Long.parseLong(value) < System.currentTimeMillis();}private boolean isTimeout(long start, long timeout) {return start + timeout > System.currentTimeMillis();}private void doUnlock() {jedis.del(lockKey);}public Condition newCondition() {// TODO Auto-generated method stubreturn null;}}

原理其实很简单，就是利用setNx和getSet这两个命令来实现。

SetNx如果返回为1，表示拿到锁，并设置超时失效时间。

getSet是一个原子操作，它是在锁超时后没释放会进入，这时有可能多个应用一同时进入，但是如果设置成功，会返回oldValue，如果两个oldvalue一样，表明拿到锁了

上面使用到的redis工具类

package com.github.distribute.lock.redis;import java.util.List;
import java.util.Map;
import java.util.Set;import org.slf4j.Logger;
import org.slf4j.LoggerFactory;import redis.clients.jedis.BinaryClient.LIST_POSITION;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;public class RedisUtil {private static final Logger LOGGER = LoggerFactory.getLogger(RedisUtil.class);private static JedisPool pool = null;private static RedisUtil ru = new RedisUtil();public static void main(String[] args) {RedisUtil redisUtil = RedisUtil.getInstance();redisUtil.set("test", "test");LOGGER.info(redisUtil.get("test"));}private RedisUtil() {if (pool == null) {String ip = "10.75.202.11";int port = 6379;JedisPoolConfig config = new JedisPoolConfig();// 控制一个pool可分配多少个jedis实例，通过pool.getResource()来获取；// 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)。config.setMaxTotal(10000);// 控制一个pool最多有多少个状态为idle(空闲的)的jedis实例。config.setMaxIdle(2000);// 表示当borrow(引入)一个jedis实例时，最大的等待时间，如果超过等待时间，则直接抛出JedisConnectionException；config.setMaxWaitMillis(1000 * 100);config.setTestOnBorrow(true);pool = new JedisPool(config, ip, port, 100000);}}public Jedis getJedis() {Jedis jedis = pool.getResource();return jedis;}public static RedisUtil getInstance() {return ru;}/*** <p>* 通过key获取储存在redis中的value* </p>* <p>* 并释放连接* </p>* * @param key* @return 成功返回value 失败返回null*/public String get(String key) {Jedis jedis = null;String value = null;try {jedis = pool.getResource();value = jedis.get(key);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return value;}/*** <p>* 向redis存入key和value,并释放连接资源* </p>* <p>* 如果key已经存在 则覆盖* </p>* * @param key* @param value* @return 成功 返回OK 失败返回 0*/public String set(String key, String value) {Jedis jedis = null;try {jedis = pool.getResource();return jedis.set(key, value);} catch (Exception e) {LOGGER.error(e.getMessage());return "0";} finally {returnResource(pool, jedis);}}/*** <p>* 删除指定的key,也可以传入一个包含key的数组* </p>* * @param keys*            一个key 也可以使 string 数组* @return 返回删除成功的个数*/public Long del(String... keys) {Jedis jedis = null;try {jedis = pool.getResource();return jedis.del(keys);} catch (Exception e) {LOGGER.error(e.getMessage());return 0L;} finally {returnResource(pool, jedis);}}/*** <p>* 通过key向指定的value值追加值* </p>* * @param key* @param str* @return 成功返回 添加后value的长度 失败 返回 添加的 value 的长度 异常返回0L*/public Long append(String key, String str) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.append(key, str);} catch (Exception e) {LOGGER.error(e.getMessage());return 0L;} finally {returnResource(pool, jedis);}return res;}/*** <p>* 判断key是否存在* </p>* * @param key* @return true OR false*/public Boolean exists(String key) {Jedis jedis = null;try {jedis = pool.getResource();return jedis.exists(key);} catch (Exception e) {LOGGER.error(e.getMessage());return false;} finally {returnResource(pool, jedis);}}/*** <p>* 设置key value,如果key已经存在则返回0,nx==> not exist* </p>* * @param key* @param value* @return 成功返回1 如果存在 和 发生异常 返回 0*/public Long setnx(String key, String value) {Jedis jedis = null;try {jedis = pool.getResource();return jedis.setnx(key, value);} catch (Exception e) {LOGGER.error(e.getMessage());return 0L;} finally {returnResource(pool, jedis);}}/*** <p>* 设置key value并制定这个键值的有效期* </p>* * @param key* @param value* @param seconds*            单位:秒* @return 成功返回OK 失败和异常返回null*/public String setex(String key, String value, int seconds) {Jedis jedis = null;String res = null;try {jedis = pool.getResource();res = jedis.setex(key, seconds, value);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key 和offset 从指定的位置开始将原先value替换* </p>* <p>* 下标从0开始,offset表示从offset下标开始替换* </p>* <p>* 如果替换的字符串长度过小则会这样* </p>* <p>* example:* </p>* <p>* value : bigsea@zto.cn* </p>* <p>* str : abc* </p>* <P>* 从下标7开始替换 则结果为* </p>* <p>* RES : bigsea.abc.cn* </p>* * @param key* @param str* @param offset*            下标位置* @return 返回替换后 value 的长度*/public Long setrange(String key, String str, int offset) {Jedis jedis = null;try {jedis = pool.getResource();return jedis.setrange(key, offset, str);} catch (Exception e) {LOGGER.error(e.getMessage());return 0L;} finally {returnResource(pool, jedis);}}/*** <p>* 通过批量的key获取批量的value* </p>* * @param keys*            string数组 也可以是一个key* @return 成功返回value的集合, 失败返回null的集合 ,异常返回空*/public List<String> mget(String... keys) {Jedis jedis = null;List<String> values = null;try {jedis = pool.getResource();values = jedis.mget(keys);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return values;}/*** <p>* 批量的设置key:value,可以一个* </p>* <p>* example:* </p>* <p>* obj.mset(new String[]{"key2","value1","key2","value2"})* </p>* * @param keysvalues* @return 成功返回OK 失败 异常 返回 null**/public String mset(String... keysvalues) {Jedis jedis = null;String res = null;try {jedis = pool.getResource();res = jedis.mset(keysvalues);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 批量的设置key:value,可以一个,如果key已经存在则会失败,操作会回滚* </p>* <p>* example:* </p>* <p>* obj.msetnx(new String[]{"key2","value1","key2","value2"})* </p>* * @param keysvalues* @return 成功返回1 失败返回0*/public Long msetnx(String... keysvalues) {Jedis jedis = null;Long res = 0L;try {jedis = pool.getResource();res = jedis.msetnx(keysvalues);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 设置key的值,并返回一个旧值* </p>* * @param key* @param value* @return 旧值 如果key不存在 则返回null*/public String getset(String key, String value) {Jedis jedis = null;String res = null;try {jedis = pool.getResource();res = jedis.getSet(key, value);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过下标 和key 获取指定下标位置的 value* </p>* * @param key* @param startOffset*            开始位置 从0 开始 负数表示从右边开始截取* @param endOffset* @return 如果没有返回null*/public String getrange(String key, int startOffset, int endOffset) {Jedis jedis = null;String res = null;try {jedis = pool.getResource();res = jedis.getrange(key, startOffset, endOffset);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key 对value进行加值+1操作,当value不是int类型时会返回错误,当key不存在是则value为1* </p>* * @param key* @return 加值后的结果*/public Long incr(String key) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.incr(key);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key给指定的value加值,如果key不存在,则这是value为该值* </p>* * @param key* @param integer* @return*/public Long incrBy(String key, Long integer) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.incrBy(key, integer);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 对key的值做减减操作,如果key不存在,则设置key为-1* </p>* * @param key* @return*/public Long decr(String key) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.decr(key);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 减去指定的值* </p>* * @param key* @param integer* @return*/public Long decrBy(String key, Long integer) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.decrBy(key, integer);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key获取value值的长度* </p>* * @param key* @return 失败返回null*/public Long serlen(String key) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.strlen(key);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key给field设置指定的值,如果key不存在,则先创建* </p>* * @param key* @param field*            字段* @param value* @return 如果存在返回0 异常返回null*/public Long hset(String key, String field, String value) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.hset(key, field, value);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key给field设置指定的值,如果key不存在则先创建,如果field已经存在,返回0* </p>* * @param key* @param field* @param value* @return*/public Long hsetnx(String key, String field, String value) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.hsetnx(key, field, value);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key同时设置 hash的多个field* </p>* * @param key* @param hash* @return 返回OK 异常返回null*/public String hmset(String key, Map<String, String> hash) {Jedis jedis = null;String res = null;try {jedis = pool.getResource();res = jedis.hmset(key, hash);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key 和 field 获取指定的 value* </p>* * @param key* @param field* @return 没有返回null*/public String hget(String key, String field) {Jedis jedis = null;String res = null;try {jedis = pool.getResource();res = jedis.hget(key, field);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key 和 fields 获取指定的value 如果没有对应的value则返回null* </p>* * @param key* @param fields*            可以使 一个String 也可以是 String数组* @return*/public List<String> hmget(String key, String... fields) {Jedis jedis = null;List<String> res = null;try {jedis = pool.getResource();res = jedis.hmget(key, fields);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key给指定的field的value加上给定的值* </p>* * @param key* @param field* @param value* @return*/public Long hincrby(String key, String field, Long value) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.hincrBy(key, field, value);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key和field判断是否有指定的value存在* </p>* * @param key* @param field* @return*/public Boolean hexists(String key, String field) {Jedis jedis = null;Boolean res = false;try {jedis = pool.getResource();res = jedis.hexists(key, field);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key返回field的数量* </p>* * @param key* @return*/public Long hlen(String key) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.hlen(key);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key 删除指定的 field* </p>* * @param key* @param fields*            可以是 一个 field 也可以是 一个数组* @return*/public Long hdel(String key, String... fields) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.hdel(key, fields);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key返回所有的field* </p>* * @param key* @return*/public Set<String> hkeys(String key) {Jedis jedis = null;Set<String> res = null;try {jedis = pool.getResource();res = jedis.hkeys(key);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key返回所有和key有关的value* </p>* * @param key* @return*/public List<String> hvals(String key) {Jedis jedis = null;List<String> res = null;try {jedis = pool.getResource();res = jedis.hvals(key);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key获取所有的field和value* </p>* * @param key* @return*/public Map<String, String> hgetall(String key) {Jedis jedis = null;Map<String, String> res = null;try {jedis = pool.getResource();res = jedis.hgetAll(key);} catch (Exception e) {// TODO} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key向list头部添加字符串* </p>* * @param key* @param strs*            可以使一个string 也可以使string数组* @return 返回list的value个数*/public Long lpush(String key, String... strs) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.lpush(key, strs);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key向list尾部添加字符串* </p>* * @param key* @param strs*            可以使一个string 也可以使string数组* @return 返回list的value个数*/public Long rpush(String key, String... strs) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.rpush(key, strs);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key在list指定的位置之前或者之后 添加字符串元素* </p>* * @param key* @param where*            LIST_POSITION枚举类型* @param pivot*            list里面的value* @param value*            添加的value* @return*/public Long linsert(String key, LIST_POSITION where, String pivot, String value) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.linsert(key, where, pivot, value);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key设置list指定下标位置的value* </p>* <p>* 如果下标超过list里面value的个数则报错* </p>* * @param key* @param index*            从0开始* @param value* @return 成功返回OK*/public String lset(String key, Long index, String value) {Jedis jedis = null;String res = null;try {jedis = pool.getResource();res = jedis.lset(key, index, value);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key从对应的list中删除指定的count个 和 value相同的元素* </p>* * @param key* @param count*            当count为0时删除全部* @param value* @return 返回被删除的个数*/public Long lrem(String key, long count, String value) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.lrem(key, count, value);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key保留list中从strat下标开始到end下标结束的value值* </p>* * @param key* @param start* @param end* @return 成功返回OK*/public String ltrim(String key, long start, long end) {Jedis jedis = null;String res = null;try {jedis = pool.getResource();res = jedis.ltrim(key, start, end);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key从list的头部删除一个value,并返回该value* </p>* * @param key* @return*/synchronized public String lpop(String key) {Jedis jedis = null;String res = null;try {jedis = pool.getResource();res = jedis.lpop(key);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key从list尾部删除一个value,并返回该元素* </p>* * @param key* @return*/synchronized public String rpop(String key) {Jedis jedis = null;String res = null;try {jedis = pool.getResource();res = jedis.rpop(key);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key从一个list的尾部删除一个value并添加到另一个list的头部,并返回该value* </p>* <p>* 如果第一个list为空或者不存在则返回null* </p>* * @param srckey* @param dstkey* @return*/public String rpoplpush(String srckey, String dstkey) {Jedis jedis = null;String res = null;try {jedis = pool.getResource();res = jedis.rpoplpush(srckey, dstkey);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key获取list中指定下标位置的value* </p>* * @param key* @param index* @return 如果没有返回null*/public String lindex(String key, long index) {Jedis jedis = null;String res = null;try {jedis = pool.getResource();res = jedis.lindex(key, index);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key返回list的长度* </p>* * @param key* @return*/public Long llen(String key) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.llen(key);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key获取list指定下标位置的value* </p>* <p>* 如果start 为 0 end 为 -1 则返回全部的list中的value* </p>* * @param key* @param start* @param end* @return*/public List<String> lrange(String key, long start, long end) {Jedis jedis = null;List<String> res = null;try {jedis = pool.getResource();res = jedis.lrange(key, start, end);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key向指定的set中添加value* </p>* * @param key* @param members*            可以是一个String 也可以是一个String数组* @return 添加成功的个数*/public Long sadd(String key, String... members) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.sadd(key, members);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key删除set中对应的value值* </p>* * @param key* @param members*            可以是一个String 也可以是一个String数组* @return 删除的个数*/public Long srem(String key, String... members) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.srem(key, members);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key随机删除一个set中的value并返回该值* </p>* * @param key* @return*/public String spop(String key) {Jedis jedis = null;String res = null;try {jedis = pool.getResource();res = jedis.spop(key);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key获取set中的差集* </p>* <p>* 以第一个set为标准* </p>* * @param keys*            可以使一个string 则返回set中所有的value 也可以是string数组* @return*/public Set<String> sdiff(String... keys) {Jedis jedis = null;Set<String> res = null;try {jedis = pool.getResource();res = jedis.sdiff(keys);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key获取set中的差集并存入到另一个key中* </p>* <p>* 以第一个set为标准* </p>* * @param dstkey*            差集存入的key* @param keys*            可以使一个string 则返回set中所有的value 也可以是string数组* @return*/public Long sdiffstore(String dstkey, String... keys) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.sdiffstore(dstkey, keys);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key获取指定set中的交集* </p>* * @param keys*            可以使一个string 也可以是一个string数组* @return*/public Set<String> sinter(String... keys) {Jedis jedis = null;Set<String> res = null;try {jedis = pool.getResource();res = jedis.sinter(keys);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key获取指定set中的交集 并将结果存入新的set中* </p>* * @param dstkey* @param keys*            可以使一个string 也可以是一个string数组* @return*/public Long sinterstore(String dstkey, String... keys) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.sinterstore(dstkey, keys);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key返回所有set的并集* </p>* * @param keys*            可以使一个string 也可以是一个string数组* @return*/public Set<String> sunion(String... keys) {Jedis jedis = null;Set<String> res = null;try {jedis = pool.getResource();res = jedis.sunion(keys);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key返回所有set的并集,并存入到新的set中* </p>* * @param dstkey* @param keys*            可以使一个string 也可以是一个string数组* @return*/public Long sunionstore(String dstkey, String... keys) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.sunionstore(dstkey, keys);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key将set中的value移除并添加到第二个set中* </p>* * @param srckey*            需要移除的* @param dstkey*            添加的* @param member*            set中的value* @return*/public Long smove(String srckey, String dstkey, String member) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.smove(srckey, dstkey, member);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key获取set中value的个数* </p>* * @param key* @return*/public Long scard(String key) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.scard(key);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key判断value是否是set中的元素* </p>* * @param key* @param member* @return*/public Boolean sismember(String key, String member) {Jedis jedis = null;Boolean res = null;try {jedis = pool.getResource();res = jedis.sismember(key, member);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key获取set中随机的value,不删除元素* </p>* * @param key* @return*/public String srandmember(String key) {Jedis jedis = null;String res = null;try {jedis = pool.getResource();res = jedis.srandmember(key);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key获取set中所有的value* </p>* * @param key* @return*/public Set<String> smembers(String key) {Jedis jedis = null;Set<String> res = null;try {jedis = pool.getResource();res = jedis.smembers(key);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key向zset中添加value,score,其中score就是用来排序的* </p>* <p>* 如果该value已经存在则根据score更新元素* </p>* * @param key* @param score* @param member* @return*/public Long zadd(String key, double score, String member) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.zadd(key, score, member);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key删除在zset中指定的value* </p>* * @param key* @param members*            可以使一个string 也可以是一个string数组* @return*/public Long zrem(String key, String... members) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.zrem(key, members);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key增加该zset中value的score的值* </p>* * @param key* @param score* @param member* @return*/public Double zincrby(String key, double score, String member) {Jedis jedis = null;Double res = null;try {jedis = pool.getResource();res = jedis.zincrby(key, score, member);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key返回zset中value的排名* </p>* <p>* 下标从小到大排序* </p>* * @param key* @param member* @return*/public Long zrank(String key, String member) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.zrank(key, member);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key返回zset中value的排名* </p>* <p>* 下标从大到小排序* </p>* * @param key* @param member* @return*/public Long zrevrank(String key, String member) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.zrevrank(key, member);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key将获取score从start到end中zset的value* </p>* <p>* socre从大到小排序* </p>* <p>* 当start为0 end为-1时返回全部* </p>* * @param key* @param start* @param end* @return*/public Set<String> zrevrange(String key, long start, long end) {Jedis jedis = null;Set<String> res = null;try {jedis = pool.getResource();res = jedis.zrevrange(key, start, end);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key返回指定score内zset中的value* </p>* * @param key* @param max* @param min* @return*/public Set<String> zrangebyscore(String key, String max, String min) {Jedis jedis = null;Set<String> res = null;try {jedis = pool.getResource();res = jedis.zrevrangeByScore(key, max, min);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key返回指定score内zset中的value* </p>* * @param key* @param max* @param min* @return*/public Set<String> zrangeByScore(String key, double max, double min) {Jedis jedis = null;Set<String> res = null;try {jedis = pool.getResource();res = jedis.zrevrangeByScore(key, max, min);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 返回指定区间内zset中value的数量* </p>* * @param key* @param min* @param max* @return*/public Long zcount(String key, String min, String max) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.zcount(key, min, max);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key返回zset中的value个数* </p>* * @param key* @return*/public Long zcard(String key) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.zcard(key);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key获取zset中value的score值* </p>* * @param key* @param member* @return*/public Double zscore(String key, String member) {Jedis jedis = null;Double res = null;try {jedis = pool.getResource();res = jedis.zscore(key, member);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key删除给定区间内的元素* </p>* * @param key* @param start* @param end* @return*/public Long zremrangeByRank(String key, long start, long end) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.zremrangeByRank(key, start, end);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key删除指定score内的元素* </p>* * @param key* @param start* @param end* @return*/public Long zremrangeByScore(String key, double start, double end) {Jedis jedis = null;Long res = null;try {jedis = pool.getResource();res = jedis.zremrangeByScore(key, start, end);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 返回满足pattern表达式的所有key* </p>* <p>* keys(*)* </p>* <p>* 返回所有的key* </p>* * @param pattern* @return*/public Set<String> keys(String pattern) {Jedis jedis = null;Set<String> res = null;try {jedis = pool.getResource();res = jedis.keys(pattern);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** <p>* 通过key判断值得类型* </p>* * @param key* @return*/public String type(String key) {Jedis jedis = null;String res = null;try {jedis = pool.getResource();res = jedis.type(key);} catch (Exception e) {LOGGER.error(e.getMessage());} finally {returnResource(pool, jedis);}return res;}/*** 返还到连接池** @param pool* @param jedis*/public static void returnResource(JedisPool pool, Jedis jedis) {if (jedis != null) {pool.returnResourceObject(jedis);}}/*** 返还到连接池** @param pool* @param jedis*/public static void returnResource(Jedis jedis) {if (jedis != null) {pool.returnResourceObject(jedis);}}
}

4、测试

写了一个简单的秒杀系统的模拟

package com.github.distribute.lock.redis;import java.util.Set;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;import redis.clients.jedis.Jedis;public class PessimisticLockTest {public static void main(String[] args) {long starTime=System.currentTimeMillis();initPrduct();initClient();printResult();long endTime=System.currentTimeMillis();long Time=endTime-starTime;System.out.println("程序运行时间： "+Time+"ms");   }/*** 输出结果*/public static void printResult() {Jedis jedis = RedisUtil.getInstance().getJedis();Set<String> set = jedis.smembers("clientList");int i = 1;for (String value : set) {System.out.println("第" + i++ + "个抢到商品，" + value + " ");}RedisUtil.returnResource(jedis);}/** 初始化顾客开始抢商品*/public static void initClient() {ExecutorService cachedThreadPool = Executors.newCachedThreadPool();int clientNum = 10000;// 模拟客户数目for (int i = 0; i < clientNum; i++) {cachedThreadPool.execute(new PessClientThread(i));}cachedThreadPool.shutdown();while (true) {if (cachedThreadPool.isTerminated()) {System.out.println("所有的线程都结束了！");break;}try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}}}/*** 初始化商品个数*/public static void initPrduct() {int prdNum = 100;// 商品个数String key = "prdNum";String clientList = "clientList";// 抢购到商品的顾客列表Jedis jedis = RedisUtil.getInstance().getJedis();if (jedis.exists(key)) {jedis.del(key);}if (jedis.exists(clientList)) {jedis.del(clientList);}jedis.set(key, String.valueOf(prdNum));// 初始化RedisUtil.returnResource(jedis);}}/*** 顾客线程* * @author linbingwen**/
class PessClientThread implements Runnable {String key = "prdNum";// 商品主键String clientList = "clientList";// // 抢购到商品的顾客列表主键String clientName;RedisBasedDistributedLock redisBasedDistributedLock;Jedis jedis = null;public PessClientThread(int num) {clientName = "编号=" + num;init();}public void init() {jedis = RedisUtil.getInstance().getJedis();redisBasedDistributedLock = new RedisBasedDistributedLock(jedis, "lock.lock", 5 * 1000);}public void run() {try {Thread.sleep((int) (Math.random() * 5000));// 随机睡眠一下} catch (InterruptedException e1) {}while (true) {//先判断缓存是否有商品if(Integer.valueOf(jedis.get(key))<= 0) {break;}//缓存还有商品，取锁，商品数目减去1System.out.println("顾客:" + clientName + "开始抢商品");if (redisBasedDistributedLock.tryLock(3,TimeUnit.SECONDS)) { //等待3秒获取锁，否则返回falseint prdNum = Integer.valueOf(jedis.get(key)); //再次取得商品缓存数目if (prdNum > 0) {jedis.decr(key);//商品数减1jedis.sadd(clientList, clientName);// 抢到商品记录一下System.out.println("好高兴，顾客:" + clientName + "抢到商品");} else {System.out.println("悲剧了，库存为0，顾客:" + clientName + "没有抢到商品");}redisBasedDistributedLock.unlock();break;}}//释放资源redisBasedDistributedLock = null;RedisUtil.returnResource(jedis);}}

输出结果：

本文源码请在这里下载：https://github.com/appleappleapple/DistributeLearning

更多技术细节请关注的笔者的公众号"单例模式"：

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在Java并发场景中,会涉及到各种各样的锁,比如:高并发编程系列:4种常用Java线程锁的特点,性能比较.使用场景,这些锁有对应的种类:公平锁,乐观锁,悲观锁等等,这篇文章来详细介绍各种锁的分类: 公 ...
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