redisTemplate (實現nx分布式鎖)

 方式1： 

獲取一個redis分布鎖

/**
     * 獲取一個redis分布鎖
     *
     * @param lockKey        鎖住的key
     * @param lockExpireMils 鎖住的時長。如果超時未解鎖，視為加鎖線程死亡，其他線程可奪取鎖
     * @return
     */
    public boolean lock(String lockKey, long lockExpireMils) {
        return (Boolean) redisTemplate.execute((RedisCallback) connection -> {
            long nowTime = System.currentTimeMillis();
            Boolean acquire = connection.setNX(lockKey.getBytes(), String.valueOf(nowTime + lockExpireMils + 1).getBytes());
            if (acquire) {
                return Boolean.TRUE;
            } else {
                byte[] value = connection.get(lockKey.getBytes());
                if (Objects.nonNull(value) && value.length > 0) {
                    long oldTime = Long.parseLong(new String(value));
                    if (oldTime < nowTime) {
                        //connection.getSet：返回這個key的舊值並設置新值。
                        byte[] oldValue = connection.getSet(lockKey.getBytes(), String.valueOf(nowTime + lockExpireMils + 1).getBytes());
                        //當key不存時會返回空，表示key不存在或者已在管道中使用
                        return oldValue == null ? false : Long.parseLong(new String(oldValue)) < nowTime;
                    }
                }
            }
            return Boolean.FALSE;
        });
    }

 

刪除鎖：（不建議，建議使用方式2的刪除） // 釋放鎖的時候，有可能因為持鎖之后方法執行時間大於鎖的有效期，此時有可能已經被另外一個線程持有鎖，所以不能直接刪除

 

/**
     * redis 解鎖：eval函數在redis集群環境中不支持， 具體查看spring源碼
     * @See JedisClusterScriptingCommands
     *
     * Object result = jedis.eval(script, Collections.singletonList(lockKey), Collections.singletonList(requestId));
     * @param lockName
     * @param uniqueId
     */
    public void unlock(String lockName, String uniqueId) {
        String lockKey = LOCK_PREFIX+lockName;
        String successMsg = StrUtil.format("{}-{}解鎖成功[Redis]！",lockName,uniqueId);
        String failMsg = StrUtil.format("{}-{}解鎖失敗[Redis]！",lockName,uniqueId);
        String script = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";
        RedisScript<Boolean> redisScript = new DefaultRedisScript(script,Boolean.class);
        Boolean result = redisTemplate.execute(redisScript, new StringRedisSerializer(), new FastJsonRedisSerializer(Boolean.class), Collections.singletonList(lockKey),uniqueId);
        printResult(result, successMsg, failMsg);
    }

 

 

 

-----------方式2---------------------------------------------

原文：https://blog.csdn.net/qq_28397259/article/details/80839072

<dependency>
    <groupId>redis.clients</groupId>
    <artifactId>jedis</artifactId>
    <version>2.9.0</version>
</dependency>

 

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.data.redis.core.RedisCallback;
import org.springframework.data.redis.core.RedisTemplate;
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;
/**
 * *************************************************************************
 * <PRE>
 *  @ClassName:    : RedisDistributedLock 
 *
 *  @Description:    : 
 *
 *  @Creation Date   : Jan 28, 2021 6:47:03 PM
 *
 *  @Author          :  Sea
 *  
 *
 * </PRE>
 **************************************************************************
 */
@Component
public class RedisDistributedLock{
 
    @Resource
    private RedisTemplate<String, Object> redisTemplate;
 
    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();
    }
 
    private final Logger logger = LoggerFactory.getLogger(RedisDistributedLock.class);
 
    public boolean setLock(String key, long expire) {
        try {
            RedisCallback<String> callback = (connection) -> {
                JedisCommands commands = (JedisCommands) connection.getNativeConnection();
                String uuid = UUID.randomUUID().toString();
                return commands.set(key, uuid, "NX", "PX", expire);
            };
            String result = redisTemplate.execute(callback);
 
            return !StringUtils.isEmpty(result);
        } catch (Exception e) {
            logger.error("set redis occured an exception", e);
        }
        return false;
    }
 
    public String get(String key) {
        try {
            RedisCallback<String> callback = (connection) -> {
                JedisCommands commands = (JedisCommands) connection.getNativeConnection();
                return commands.get(key);
            };
            String result = redisTemplate.execute(callback);
            return result;
        } catch (Exception e) {
            logger.error("get redis occured an exception", e);
        }
        return "";
    }
 
    public boolean releaseLock(String key,String requestId) {
        // 釋放鎖的時候，有可能因為持鎖之后方法執行時間大於鎖的有效期，此時有可能已經被另外一個線程持有鎖，所以不能直接刪除
        try {
            List<String> keys = new ArrayList<>();
            keys.add(key);
            List<String> args = new ArrayList<>();
            args.add(requestId);
 
            // 使用lua腳本刪除redis中匹配value的key，可以避免由於方法執行時間過長而redis鎖自動過期失效的時候誤刪其他線程的鎖
            // spring自帶的執行腳本方法中，集群模式直接拋出不支持執行腳本的異常，所以只能拿到原redis的connection來執行腳本
            RedisCallback<Long> callback = (connection) -> {
                Object nativeConnection = connection.getNativeConnection();
                // 集群模式和單機模式雖然執行腳本的方法一樣，但是沒有共同的接口，所以只能分開執行
                // 集群模式
                if (nativeConnection instanceof JedisCluster) {
                    return (Long) ((JedisCluster) nativeConnection).eval(UNLOCK_LUA, keys, args);
                }
 
                // 單機模式
                else if (nativeConnection instanceof Jedis) {
                    return (Long) ((Jedis) nativeConnection).eval(UNLOCK_LUA, keys, args);
                }
                return 0L;
            };
            Long result = redisTemplate.execute(callback);
 
            return result != null && result > 0;
        } catch (Exception e) {
            logger.error("release lock occured an exception", e);
        } finally {
            // 清除掉ThreadLocal中的數據，避免內存溢出
            //lockFlag.remove();
        }
        return false;
    }
 
}

 

不管是加鎖還是解鎖，都要保持操作的原子性，否則就有可能產生死鎖。

springboot 項目 redisTempalte 配置

pring.redis.database=0
spring.redis.host=127.0.0.1
spring.redis.port=6379
#spring.redis.password=root
#springboot2.x  need unit   ,db connect time out 
spring.redis.timeout=60s
spring.redis.jedis.pool.max-active=-1
spring.redis.jedis.pool.max-wait=-1s
spring.redis.jedis.pool.max-idle=300
spring.redis.jedis.pool.min-idle=5

 

       <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>

 

 

 

配置類：

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.cache.CacheManager;
import org.springframework.cache.annotation.CachingConfigurerSupport;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.cache.interceptor.KeyGenerator;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.cache.RedisCacheManager;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;
import java.lang.reflect.Method;
 
 
@Configuration
@EnableCaching
public class RedisConfig extends CachingConfigurerSupport {
 
    @Bean
    public KeyGenerator keyGenerator() {
        return new KeyGenerator() {
 
            @Override
            public Object generate(Object target, Method method, Object... params) {
                StringBuilder sb = new StringBuilder();
                sb.append(target.getClass().getName());
                sb.append(method.getName());
                for (Object obj : params) {
                    sb.append(obj.toString());
                }
                return sb.toString();
            }
        };
 
    }
 
    /**
     * 管理緩存
     *
     * @param redisTemplate
     * @return
     */
 
    @SuppressWarnings("rawtypes")
    @Bean
    public CacheManager CacheManager(RedisTemplate redisTemplate) {
        RedisCacheManager rcm = new RedisCacheManager(redisTemplate);
        return rcm;
    }
 
 
    /**
     * redisTemplate配置
     *
     * @param factory
     * @return
     */
    @SuppressWarnings({ "rawtypes", "unchecked" })
    @Bean
    public RedisTemplate<String, String> redisTemplate(RedisConnectionFactory factory) {
        StringRedisTemplate template = new StringRedisTemplate(factory);
        Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);
        ObjectMapper om = new ObjectMapper();
        om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
        om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
        jackson2JsonRedisSerializer.setObjectMapper(om);
        template.setValueSerializer(jackson2JsonRedisSerializer);
        template.afterPropertiesSet();
        return template;
    }
}