項目中,使用@Cacheable進行數據緩存。發現：當redis宕機之后，@Cacheable注解的方法并未進行緩存沖突，而是直接拋出異常。而這樣的異常會導致服務不可用。

我們是通過@EnableCaching進行緩存啟用的，因此可以先看@EnableCaching的相關注釋

通過@EnableCaching的類注釋可發現,spring cache的核心配置接口為：org.springframework.cache.annotation.CachingConfigurer

/** * Interface to be implemented by @{@link org.springframework.context.annotation.Configuration * Configuration} classes annotated with @{@link EnableCaching} that wish or need to * specify explicitly how caches are resolved and how keys are generated for annotation-driven * cache management. Consider extending {@link CachingConfigurerSupport}, which provides a * stub implementation of all interface methods. * * <p>See @{@link EnableCaching} for general examples and context; see * {@link #cacheManager()}, {@link #cacheResolver()} and {@link #keyGenerator()} * for detailed instructions. * * @author Chris Beams * @author Stephane Nicoll * @since 3.1 * @see EnableCaching * @see CachingConfigurerSupport */public interface CachingConfigurer { /** * Return the cache manager bean to use for annotation-driven cache * management. A default {@link CacheResolver} will be initialized * behind the scenes with this cache manager. For more fine-grained * management of the cache resolution, consider setting the * {@link CacheResolver} directly. * <p>Implementations must explicitly declare * {@link org.springframework.context.annotation.Bean @Bean}, e.g. * <pre class='code'> * Configuration * EnableCaching * public class AppConfig extends CachingConfigurerSupport { * Bean // important! * Override * public CacheManager cacheManager() { * // configure and return CacheManager instance * } * // ... * } * </pre> * See @{@link EnableCaching} for more complete examples. */ CacheManager cacheManager(); /** * Return the {@link CacheResolver} bean to use to resolve regular caches for * annotation-driven cache management. This is an alternative and more powerful * option of specifying the {@link CacheManager} to use. * <p>If both a {@link #cacheManager()} and {@code #cacheResolver()} are set, * the cache manager is ignored. * <p>Implementations must explicitly declare * {@link org.springframework.context.annotation.Bean @Bean}, e.g. * <pre class='code'> * Configuration * EnableCaching * public class AppConfig extends CachingConfigurerSupport { * Bean // important! * Override * public CacheResolver cacheResolver() { * // configure and return CacheResolver instance * } * // ... * } * </pre> * See {@link EnableCaching} for more complete examples. */ CacheResolver cacheResolver(); /** * Return the key generator bean to use for annotation-driven cache management. * Implementations must explicitly declare * {@link org.springframework.context.annotation.Bean @Bean}, e.g. * <pre class='code'> * Configuration * EnableCaching * public class AppConfig extends CachingConfigurerSupport { * Bean // important! * Override * public KeyGenerator keyGenerator() { * // configure and return KeyGenerator instance * } * // ... * } * </pre> * See @{@link EnableCaching} for more complete examples. */ KeyGenerator keyGenerator(); /** * Return the {@link CacheErrorHandler} to use to handle cache-related errors. * <p>By default,{@link org.springframework.cache.interceptor.SimpleCacheErrorHandler} * is used and simply throws the exception back at the client. * <p>Implementations must explicitly declare * {@link org.springframework.context.annotation.Bean @Bean}, e.g. * <pre class='code'> * Configuration * EnableCaching * public class AppConfig extends CachingConfigurerSupport { * Bean // important! * Override * public CacheErrorHandler errorHandler() { * // configure and return CacheErrorHandler instance * } * // ... * } * </pre> * See @{@link EnableCaching} for more complete examples. */ CacheErrorHandler errorHandler();}

該接口errorHandler方法可配置異常的處理方式。通過該方法上的注釋可以發現,默認的CacheErrorHandler實現類是org.springframework.cache.interceptor.SimpleCacheErrorHandler

/** * A simple {@link CacheErrorHandler} that does not handle the * exception at all, simply throwing it back at the client. * * @author Stephane Nicoll * @since 4.1 */public class SimpleCacheErrorHandler implements CacheErrorHandler { @Override public void handleCacheGetError(RuntimeException exception, Cache cache, Object key) { throw exception; } @Override public void handleCachePutError(RuntimeException exception, Cache cache, Object key, Object value) { throw exception; } @Override public void handleCacheEvictError(RuntimeException exception, Cache cache, Object key) { throw exception; } @Override public void handleCacheClearError(RuntimeException exception, Cache cache) { throw exception; }}

SimpleCacheErrorHandler類注釋上說明的很清楚：對cache的異常不做任何處理，直接將該異常拋給客戶端。因此默認的情況下，redis服務器異常后，直接就阻斷了正常業務

通過上面的分析可知，我們可以通過自定義CacheErrorHandler來干預@Cacheable的異常處理邏輯。具體代碼如下：

public class RedisConfig extends CachingConfigurerSupport { /** * redis數據操作異常處理。該方法處理邏輯：在日志中打印出錯誤信息，但是放行。 * 保證redis服務器出現連接等問題的時候不影響程序的正常運行 */ @Override public CacheErrorHandler errorHandler() { return new CacheErrorHandler() { @Override public void handleCachePutError(RuntimeException exception, Cache cache, Object key, Object value) {handleRedisErrorException(exception, key); } @Override public void handleCacheGetError(RuntimeException exception, Cache cache, Object key) {handleRedisErrorException(exception, key); } @Override public void handleCacheEvictError(RuntimeException exception, Cache cache, Object key) {handleRedisErrorException(exception, key); } @Override public void handleCacheClearError(RuntimeException exception, Cache cache) {handleRedisErrorException(exception, null); } }; } protected void handleRedisErrorException(RuntimeException exception, Object key) { log.error('redis異常：key=[{}]', key, exception); }}

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