redis实现分布式锁解决本地事务
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2024-01-05 10:40:40
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1.springRedis实现分布式锁
import org.springframework.data.redis.core.RedisCallback;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;
import org.springframework.util.StringUtils;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisCluster;
import redis.clients.jedis.JedisCommands;
import javax.annotation.Resource;
import java.util.ArrayList;
import java.util.List;
import java.util.UUID;
/**
* @author superchen
* @since 2018/5/16
**/
@Component
public class RedisDistributedLock {
@Resource
private StringRedisTemplate stringRedisTemplate;
public static final String UNLOCK_LUA;
//静态代码块初始化lua脚本 作用:key和value匹配则删除
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();
}
/*
* 获取锁
* */
public boolean setLock(String key, long expire) {
try {
//lambda表达式 jdk8及以上支持 替换原类的匿名内部类
RedisCallback<String> callback = (connection) -> {
JedisCommands commands = (JedisCommands) connection.getNativeConnection();
String uuid = UUID.randomUUID().toString();
return commands.set(key, uuid, "NX", "PX", expire);
};
String result = stringRedisTemplate.execute(callback);
return !StringUtils.isEmpty(result);
} catch (Exception e) {
System.out.println("set redis occured an exception");
}
return false;
}
/*
* 根据key获取对应的值
* */
public String get(String key) {
try {
RedisCallback<String> callback = (connection) -> {
JedisCommands commands = (JedisCommands) connection.getNativeConnection();
return commands.get(key);
};
String result = stringRedisTemplate.execute(callback);
return result;
} catch (Exception e) {
System.out.println("get redis occured an exception");
}
return "";
}
/*
* 释放锁
* 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(这种情况通常是由于过期时间设置不合理导致)
* */
public boolean releaseLock(String key, String requestId) {
try {
List<String> keys = new ArrayList<>();
keys.add(key);
List<String> args = new ArrayList<>();
args.add(requestId);
// 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
RedisCallback<Long> callback = (connection) -> {
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;
};
Long result = stringRedisTemplate.execute(callback);
return result != null && result > 0;
} catch (Exception e) {
System.out.println("release lock occured an exception");
} finally {
// 清除掉ThreadLocal中的数据,避免内存溢出
//lockFlag.remove();
}
return false;
}
}
2.业务代码中使用分布式锁
import com.sinosoft.xplatform.core.sysmng.sysuser.dao.CgpConfigDao;
import com.sinosoft.xplatform.core.sysmng.sysuser.entity.CgpConfig;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class TestService {
private String requestId;
private static final String key = "testKey";
@Autowired
private RedisDistributedLock redisDistributedLock;
@Autowired
private CgpConfigDao cgpConfigDao;
public void getMoney(){
//获得锁 1.键 2.过期时间(根据具体业务设置)
boolean lockOk = redisDistributedLock.setLock(key, 3600000);
try {
if (lockOk) {
requestId = redisDistributedLock.get(key); //记录当前锁对应的value(UUID)
String valueStr = cgpConfigDao.findSyncUserSystems("test", "test");//查询剩余额度
int value = Integer.parseInt(valueStr);
System.out.println("初始化查询结果value = "+value);
//延时模拟业务逻辑处理 开始
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
//延时模拟业务逻辑处理 结束
if(value >= 100){
System.out.println("余额充足-----{}");
value -= 20;
//将改变后的结果保存至数据库
CgpConfig cgpConfig = new CgpConfig();
cgpConfig.setCconPid(225);
cgpConfig.setConfigCode("test");
cgpConfig.setConfigType("test");
cgpConfig.setValidity("A");
cgpConfig.setConfigValue(value+"");
cgpConfigDao.save(cgpConfig);
}else{
System.out.println("余额不足----{}");
}
}else{
//此时锁已被占用,可以直接返回 也可以自己实现重试机制(根据业务需求处理即可)
System.out.println("get no lock----{}");
}
} catch (Exception ex) {
System.out.println("test error");
} finally {
//无论处理结果如何一定要释放锁 虽然有过期时间不会导致死锁,但如果有重试机制则会极大影响执行效率。
if (requestId != null)
redisDistributedLock.releaseLock(key, requestId);
}
}
}
3.参考: