springboot(20)Redis缓存@Cacheable对存在的数据返回null
祈雨的笔记
·
2018-06-08
·
via 祈雨的笔记
问题描述
最近我们用Spring Cache + redis来做缓存，使用的是1.8.10.RELEASE版本的spring-data-redis。在高并发下数据库存在数据但是@Cacheable 注解返回的内容是null。查看了一下源代码，在使用注解获取缓存的时候，RedisCache的get方法会先去判断key是否存在，然后再去获取值。这了就有一个漏铜，当线程1判断了key是存在的，紧接着这个时候这个key过期了，这时线程1再去获取值的时候返回的是null。
org.springframework.data.redis.cache.RedisCache.get(RedisCacheKey)方法源码：
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| public RedisCacheElement get(final RedisCacheKey cacheKey) {
Assert.notNull(cacheKey, "CacheKey must not be null!");
Boolean exists = (Boolean) redisOperations.execute(new RedisCallback<Boolean>() {
@Override
public Boolean doInRedis(RedisConnection connection) throws DataAccessException {
return connection.exists(cacheKey.getKeyBytes());
}
});
if (!exists.booleanValue()) {
return null;
}
return new RedisCacheElement(cacheKey, fromStoreValue(lookup(cacheKey)));
}
protected Object lookup(Object key) {
RedisCacheKey cacheKey = key instanceof RedisCacheKey ? (RedisCacheKey) key : getRedisCacheKey(key);
byte[] bytes = (byte[]) redisOperations.execute(new AbstractRedisCacheCallback<byte[]>(
new BinaryRedisCacheElement(new RedisCacheElement(cacheKey, null), cacheValueAccessor), cacheMetadata) {
@Override
public byte[] doInRedis(BinaryRedisCacheElement element, RedisConnection connection) throws DataAccessException {
return connection.get(element.getKeyBytes());
}
});
return bytes == null ? null : cacheValueAccessor.deserializeIfNecessary(bytes);
}
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解决方案
更换版本：spring-data-redis在1.8.11的版本中修复了该问题
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| <dependency>
<groupId>org.springframework.data</groupId>
<artifactId>spring-data-redis</artifactId>
<version>1.8.11.RELEASE</version>
</dependency>
|
1.8.11的源代码:
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| public RedisCacheElement get(final RedisCacheKey cacheKey) {
Assert.notNull(cacheKey, "CacheKey must not be null!");
Boolean exists = (Boolean) redisOperations.execute(new RedisCallback<Boolean>() {
@Override
public Boolean doInRedis(RedisConnection connection) throws DataAccessException {
return connection.exists(cacheKey.getKeyBytes());
}
});
if (!exists) {
return null;
}
byte[] bytes = doLookup(cacheKey);
if (bytes == null) {
return null;
}
return new RedisCacheElement(cacheKey, fromStoreValue(deserialize(bytes)));
}
private byte[] doLookup(Object key) {
RedisCacheKey cacheKey = key instanceof RedisCacheKey ? (RedisCacheKey) key : getRedisCacheKey(key);
return (byte[]) redisOperations.execute(new AbstractRedisCacheCallback<byte[]>(
new BinaryRedisCacheElement(new RedisCacheElement(cacheKey, null), cacheValueAccessor), cacheMetadata) {
@Override
public byte[] doInRedis(BinaryRedisCacheElement element, RedisConnection connection) throws DataAccessException {
return connection.get(element.getKeyBytes());
}
});
}
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配置Redis管理器
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| @Configuration
public class RedisConfig {
@Bean
public CacheManager cacheManager(RedisTemplate<String,?> redisTemplate) {
RedisCacheManager cacheManager= new RedisCacheManager(redisTemplate);
cacheManager.setUsePrefix(true);
cacheManager.setDefaultExpiration(60);
return cacheManager;
}
}
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