增强Spring改造@CacheEvict，支持缓存批量模糊删除！

系统中集成了Spring cache 使用@CacheEvict进行缓存清除，@CacheEvict可以清除指定的key，同时可以指定allEntries = true清空namespace下的所有元素，现在遇到一个问题使用allEntries = true清空namespace的值只能是常量，但是我现在需要将缓存根据租户的唯一TelnetID进行分离，这就导致allEntries = true不能使用了，否则一旦触发清除缓存，将会导致全部的缓存清空，而我只想清空当前租户的缓存，熟悉redis命令的人都知道，查询和删除都可以做模糊匹配，所以我就想让SpringCache的@CacheEvict也支持模糊匹配清除。

先去搞清楚@CacheEvict是怎么实现缓存清理的，因为之前看过redis的源码，知道@CacheEvict是通过AOP实现的，其中核心的类是CacheAspectSupport，具体的源码分析细节大家可以自行Google，我只简单的分析一下CacheAspectSupport这个类里面重点的几个方法

private Object execute(final CacheOperationInvoker invoker, Method method, CacheOperationContexts contexts) {
// Special handling of synchronized invocation
if (contexts.isSynchronized()) {
CacheOperationContext context = contexts.get(CacheableOperation.class).iterator().next();
if (isConditionPassing(context, CacheOperationExpressionEvaluator.NO_RESULT)) {
Object key = generateKey(context, CacheOperationExpressionEvaluator.NO_RESULT);
Cache cache = context.getCaches().iterator().next();
try {
return wrapCacheValue(method, cache.get(key, () -> unwrapReturnValue(invokeOperation(invoker))));
catch (Cache.ValueRetrievalException ex) {
// The invoker wraps any Throwable in a ThrowableWrapper instance so we
// can just make sure that one bubbles up the stack.
throw (CacheOperationInvoker.ThrowableWrapper) ex.getCause();

else {
// No caching required, only call the underlying method
return invokeOperation(invoker);


// Process any early evictions
processCacheEvicts(contexts.get(CacheEvictOperation.class), true,
CacheOperationExpressionEvaluator.NO_RESULT);

// Check if we have a cached item matching the conditions
Cache.ValueWrapper cacheHit = findCachedItem(contexts.get(CacheableOperation.class));

// Collect puts from any @Cacheable miss, if no cached item is found
List cachePutRequests = new LinkedList<>();
if (cacheHit == null) {
collectPutRequests(contexts.get(CacheableOperation.class),
CacheOperationExpressionEvaluator.NO_RESULT, cachePutRequests);
}

Object cacheValue;
Object returnValue;

if (cacheHit != null && !hasCachePut(contexts)) {
// If there are no put requests, just use the cache hit
cacheValue = cacheHit.get();
returnValue = wrapCacheValue(method, cacheValue);
}
else {
// Invoke the method if we don't have a cache hit
returnValue = invokeOperation(invoker);
cacheValue = unwrapReturnValue(returnValue);
}
// Collect any explicit @CachePuts
collectPutRequests(contexts.get(CachePutOperation.class), cacheValue, cachePutRequests);
// Process any collected put requests, either from @CachePut or a @Cacheable miss
for (CachePutRequest cachePutRequest : cachePutRequests) {
cachePutRequest.apply(cacheValue);
}
// Process any late evictions
processCacheEvicts(contexts.get(CacheEvictOperation.class), false, cacheValue);
return returnValue;
}


这个方法是缓存控制入口核心方法processCacheEvicts会根据CacheOperationContext进行缓存清理处理，我们可以看到调用的一个performCacheEvict方法

private void performCacheEvict(
CacheOperationContext context, CacheEvictOperation operation, @Nullable Object result) {

Object key = null;
for (Cache cache : context.getCaches()) {
if (operation.isCacheWide()) { // 如果allEntries为ture就执行这个逻辑
logInvalidating(context, operation, null);
doClear(cache);
}
else {// 否则执行删除指定的key
if (key == null) {
key = generateKey(context, result);
}
logInvalidating(context, operation, key);
doEvict(cache, key);
}
}
}


看到这里，我们就知道怎么回事了，继续debug跟进去，看到doClear和doEvict最终分别会调用RedisCache中的evict和clear方法

@Override
public void evict(Object key) {
cacheWriter.remove(name, createAndConvertCacheKey(key));


/*
* (non-Javadoc)
* @see org.springframework.cache.Cache#clear()
*/
@Override
public void clear() {
// 支持模糊删除
byte[] pattern = conversionService.convert(createCacheKey("*"), byte[].class);
cacheWriter.clean(name, pattern);
}


我们看到如果allEntries为ture的时候最终执行的是clear()这个方法，其实他也是模糊删除的，只是他的key规则是namespace:: *，看到这里就看到希望了我们只需要想办法在namespace *中插入我们的telnetID就可以变成namespace ::telnetID:*这种格式，也就达到了我们的目的了。

重点需要重写RedisCache的evict方法，新建一个RedisCacheResolver集成RedisCache，重写evict方法

public class RedisCacheResolver extends RedisCache {

private final String name;
private final RedisCacheWriter cacheWriter;
private final ConversionService conversionService;

protected RedisCacheResolver(String name, RedisCacheWriter cacheWriter, RedisCacheConfiguration cacheConfig) {
super(name, cacheWriter, cacheConfig);
this.name = name;
this.cacheWriter = cacheWriter;
this.conversionService = cacheConfig.getConversionService();
}

/**
*
* @Title: evict
* @Description: 重写删除的方法
* @param @param key
* @throws
*
*/
@Override
public void evict(Object key) {
// 如果key中包含"noCacheable:"关键字的，就不进行缓存处理
if (key.toString().contains(RedisConstant.NO_CACHEABLE)) {
return;
}

if (key instanceof String) {
String keyString = key.toString();
// 后缀删除
if (StringUtils.endsWith(keyString, "*")) {
evictLikeSuffix(keyString);
return;
}
}
// 删除指定的key
super.evict(key);
}

/**
* 后缀匹配匹配
*
* @param key
*/
private void evictLikeSuffix(String key) {
byte[] pattern = this.conversionService.convert(this.createCacheKey(key), byte[].class);
this.cacheWriter.clean(this.name, pattern);
}
}


现在我们需要让我们的这个RedisCacheResolver生效，所以需要将我们的RedisCacheResolver 注入到RedisCacheManager中，因此我们需要定义一个我们自己的RedisCacheManagerResolver集成z

public class RedisCacheManagerResolver extends RedisCacheManager {
private final RedisCacheWriter cacheWriter;
private final RedisCacheConfiguration defaultCacheConfig;

public RedisCacheManagerResolver(RedisCacheWriter cacheWriter, RedisCacheConfiguration defaultCacheConfiguration) {
super(cacheWriter, defaultCacheConfiguration);
this.cacheWriter = cacheWriter;
this.defaultCacheConfig = defaultCacheConfiguration;
}

public RedisCacheManagerResolver(RedisCacheWriter cacheWriter, RedisCacheConfiguration defaultCacheConfiguration, String... initialCacheNames) {
super(cacheWriter, defaultCacheConfiguration, initialCacheNames);
this.cacheWriter = cacheWriter;
this.defaultCacheConfig = defaultCacheConfiguration;
}

public RedisCacheManagerResolver(RedisCacheWriter cacheWriter, RedisCacheConfiguration defaultCacheConfiguration, boolean allowInFlightCacheCreation, String... initialCacheNames) {
super(cacheWriter, defaultCacheConfiguration, allowInFlightCacheCreation, initialCacheNames);
this.cacheWriter = cacheWriter;
this.defaultCacheConfig = defaultCacheConfiguration;
}

public RedisCacheManagerResolver(RedisCacheWriter cacheWriter, RedisCacheConfiguration defaultCacheConfiguration, Map initialCacheConfigurations) {
super(cacheWriter, defaultCacheConfiguration, initialCacheConfigurations);
this.cacheWriter = cacheWriter;
this.defaultCacheConfig = defaultCacheConfiguration;
}

public RedisCacheManagerResolver(RedisCacheWriter cacheWriter, RedisCacheConfiguration defaultCacheConfiguration, Map initialCacheConfigurations, boolean allowInFlightCacheCreation) {
super(cacheWriter, defaultCacheConfiguration, initialCacheConfigurations, allowInFlightCacheCreation);
this.cacheWriter = cacheWriter;
this.defaultCacheConfig = defaultCacheConfiguration;
}

public RedisCacheManagerResolver(RedisConnectionFactory redisConnectionFactory, RedisCacheConfiguration cacheConfiguration) {
this(RedisCacheWriter.nonLockingRedisCacheWriter(redisConnectionFactory),cacheConfiguration);
}

/**
* 覆盖父类创建RedisCache，采用自定义的RedisCacheResolver
* @Title: createRedisCache
* @Description: TODO
* @param @param name
* @param @param cacheConfig
* @param @return
* @throws
*
*/
@Override
protected RedisCache createRedisCache(String name, @Nullable RedisCacheConfiguration cacheConfig) {
return new RedisCacheResolver(name, cacheWriter, cacheConfig != null ? cacheConfig : defaultCacheConfig);
}

@Override
public Map getCacheConfigurations() {
Map configurationMap = new HashMap<>(getCacheNames().size());
getCacheNames().forEach(it -> {
RedisCache cache = RedisCacheResolver.class.cast(lookupCache(it));
configurationMap.put(it, cache != null ? cache.getCacheConfiguration() : null);
});
return Collections.unmodifiableMap(configurationMap);
}
}


至此我们就完成了关键的步骤，最后只需要RedisConfig中管理我们自己的RedisCacheManagerResolver即可。Java技术进阶路线：https://www.yoodb.com/

public CacheManager cacheManager(RedisConnectionFactory redisConnectionFactory) {
// 设置全局过期时间，单位为秒
Duration timeToLive = Duration.ZERO;
timeToLive = Duration.ofSeconds(timeOut);
// RedisCacheManager cacheManager = new RedisCacheManager(
// RedisCacheWriter.nonLockingRedisCacheWriter(redisConnectionFactory),
// this.getRedisCacheConfigurationWithTtl(timeToLive), // 默认策略，未配置的 value 会使用这个
// this.getRedisCacheConfigurationMap() // 指定 value策略
RedisCacheManagerResolver cacheManager =
new RedisCacheManagerResolver(RedisCacheWriter.nonLockingRedisCacheWriter(redisConnectionFactory),
this.getRedisCacheConfigurationWithTtl(timeToLive), // 默认策略，未配置的 value 会使用这个
this.getRedisCacheConfigurationMap() // 指定 value策略


// RedisCacheManager cacheManager = RedisCacheManager.builder(factory).cacheDefaults(config).build();
return cacheManager;
}


经过上面的步骤，我们已经实现了重写evict方法，用来模糊删除缓存了

@CacheEvict(value = "BASE_CACHE, key = "#modelClassName + #telenetId+ '*'", allEntries = false)


只需要用上面这个注解，我们就可以删除telnetID下所有的缓存了。

作者：Crystalqy https://blog.csdn.net/Crystalqy/article/details/110681684

公众号“Java精选”所发表内容注明来源的，版权归原出处所有（无法查证版权的或者未注明出处的均来自网络，系转载，转载的目的在于传递更多信息，版权属于原作者。如有侵权，请联系，笔者会第一时间删除处理！

最近有很多人问，有没有读者交流群！加入方式很简单，公众号Java精选，回复“加群”，即可入群！

（微信小程序）：3000+道面试题，包含Java基础、并发、JVM、线程、MQ系列、Redis、Spring系列、Elasticsearch、Docker、K8s、Flink、Spark、架构设计等，在线随时刷题！

特别推荐：专注分享最前沿的技术与资讯，为弯道超车做好准备及各种开源项目与高效率软件的公众号，「大咖笔记」，专注挖掘好东西，非常值得大家关注。点击下方公众号卡片关注。

文章有帮助的话，点在看，转发吧！