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本文主要研究一下jetcache的MultiLevelCache
Cache
jetcache-core/src/main/java/com/alicp/jetcache/Cache.java
代码语言：javascript复制public interface Cache<K, V> extends Closeable {
Logger logger = LoggerFactory.getLogger(Cache.class);
default V get(K key) throws CacheInvokeException {
CacheGetResult<V> result = GET(key);
if (result.isSuccess()) {
return result.getValue();
} else {
return null;
}
}
default Map<K, V> getAll(Set<? extends K> keys) throws CacheInvokeException {
MultiGetResult<K, V> cacheGetResults = GET_ALL(keys);
return cacheGetResults.unwrapValues();
}
default void put(K key, V value) {
PUT(key, value);
}
default void putAll(Map<? extends K, ? extends V> map) {
PUT_ALL(map);
}
default boolean putIfAbsent(K key, V value) {
CacheResult result = PUT_IF_ABSENT(key, value, config().getExpireAfterWriteInMillis(), TimeUnit.MILLISECONDS);
return result.getResultCode() == CacheResultCode.SUCCESS;
}
default boolean remove(K key) {
return REMOVE(key).isSuccess();
}
default void removeAll(Set<? extends K> keys) {
REMOVE_ALL(keys);
}
<T> T unwrap(Class<T> clazz);
@Override
default void close() {
}
CacheConfig<K, V> config();
default AutoReleaseLock tryLock(K key, long expire, TimeUnit timeUnit) {
if (key == null) {
return null;
}
final String uuid = UUID.randomUUID().toString();
final long expireTimestamp = System.currentTimeMillis() timeUnit.toMillis(expire);
final CacheConfig config = config();
AutoReleaseLock lock = () -> {
int unlockCount = 0;
while (unlockCount < config.getTryLockUnlockCount()) {
if(System.currentTimeMillis() < expireTimestamp) {
CacheResult unlockResult = REMOVE(key);
if (unlockResult.getResultCode() == CacheResultCode.FAIL
|| unlockResult.getResultCode() == CacheResultCode.PART_SUCCESS) {
logger.info("[tryLock] [{} of {}] [{}] unlock failed. Key={}, msg = {}",
unlockCount, config.getTryLockUnlockCount(), uuid, key, unlockResult.getMessage());
// retry
} else if (unlockResult.isSuccess()) {
logger.debug("[tryLock] [{} of {}] [{}] successfully release the lock. Key={}",
unlockCount, config.getTryLockUnlockCount(), uuid, key);
return;
} else {
logger.warn("[tryLock] [{} of {}] [{}] unexpected unlock result: Key={}, result={}",
unlockCount, config.getTryLockUnlockCount(), uuid, key, unlockResult.getResultCode());
return;
}
} else {
logger.info("[tryLock] [{} of {}] [{}] lock already expired: Key={}",
unlockCount, config.getTryLockUnlockCount(), uuid, key);
return;
}
}
};
int lockCount = 0;
Cache cache = this;
while (lockCount < config.getTryLockLockCount()) {
CacheResult lockResult = cache.PUT_IF_ABSENT(key, uuid, expire, timeUnit);
if (lockResult.isSuccess()) {
logger.debug("[tryLock] [{} of {}] [{}] successfully get a lock. Key={}",
lockCount, config.getTryLockLockCount(), uuid, key);
return lock;
} else if (lockResult.getResultCode() == CacheResultCode.FAIL || lockResult.getResultCode() == CacheResultCode.PART_SUCCESS) {
logger.info("[tryLock] [{} of {}] [{}] cache access failed during get lock, will inquiry {} times. Key={}, msg={}",
lockCount, config.getTryLockLockCount(), uuid,
config.getTryLockInquiryCount(), key, lockResult.getMessage());
int inquiryCount = 0;
while (inquiryCount < config.getTryLockInquiryCount()) {
CacheGetResult inquiryResult = cache.GET(key);
if (inquiryResult.isSuccess()) {
if (uuid.equals(inquiryResult.getValue())) {
logger.debug("[tryLock] [{} of {}] [{}] successfully get a lock after inquiry. Key={}",
inquiryCount, config.getTryLockInquiryCount(), uuid, key);
return lock;
} else {
logger.debug("[tryLock] [{} of {}] [{}] not the owner of the lock, return null. Key={}",
inquiryCount, config.getTryLockInquiryCount(), uuid, key);
return null;
}
} else {
logger.info("[tryLock] [{} of {}] [{}] inquiry failed. Key={}, msg={}",
inquiryCount, config.getTryLockInquiryCount(), uuid, key, inquiryResult.getMessage());
// retry inquiry
}
}
} else {
// others holds the lock
logger.debug("[tryLock] [{} of {}] [{}] others holds the lock, return null. Key={}",
lockCount, config.getTryLockLockCount(), uuid, key);
return null;
}
}
logger.debug("[tryLock] [{}] return null after {} attempts. Key={}", uuid, config.getTryLockLockCount(), key);
return null;
}
default boolean tryLockAndRun(K key, long expire, TimeUnit timeUnit, Runnable action){
try (AutoReleaseLock lock = tryLock(key, expire, timeUnit)) {
if (lock != null) {
action.run();
return true;
} else {
return false;
}
}
}
CacheGetResult<V> GET(K key);
MultiGetResult<K, V> GET_ALL(Set<? extends K> keys);
default V computeIfAbsent(K key, Function<K, V> loader) {
return computeIfAbsent(key, loader, config().isCacheNullValue());
}
V computeIfAbsent(K key, Function<K, V> loader, boolean cacheNullWhenLoaderReturnNull);
V computeIfAbsent(K key, Function<K, V> loader, boolean cacheNullWhenLoaderReturnNull, long expireAfterWrite, TimeUnit timeUnit);
default void put(K key, V value, long expireAfterWrite, TimeUnit timeUnit) {
PUT(key, value, expireAfterWrite, timeUnit);
}
default CacheResult PUT(K key, V value) {
if (key == null) {
return CacheResult.FAIL_ILLEGAL_ARGUMENT;
}
return PUT(key, value, config().getExpireAfterWriteInMillis(), TimeUnit.MILLISECONDS);
}
CacheResult PUT(K key, V value, long expireAfterWrite, TimeUnit timeUnit);
default void putAll(Map<? extends K, ? extends V> map, long expireAfterWrite, TimeUnit timeUnit) {
PUT_ALL(map, expireAfterWrite, timeUnit);
}
default CacheResult PUT_ALL(Map<? extends K, ? extends V> map) {
if (map == null) {
return CacheResult.FAIL_ILLEGAL_ARGUMENT;
}
return PUT_ALL(map, config().getExpireAfterWriteInMillis(), TimeUnit.MILLISECONDS);
}
CacheResult PUT_ALL(Map<? extends K, ? extends V> map, long expireAfterWrite, TimeUnit timeUnit);
CacheResult REMOVE(K key);
CacheResult REMOVE_ALL(Set<? extends K> keys);
CacheResult PUT_IF_ABSENT(K key, V value, long expireAfterWrite, TimeUnit timeUnit);
}
Cache接口主要是定义了大写的GET、GET_ALL、PUT、PUT_ALL、REMOVE、REMOVE_ALL、PUT_IF_ABSENT方法，以及基于这些大写方法包装的小写default方法 V get(K key)这样的方法虽然用起来方便，但有功能上的缺陷，当get返回null的时候，无法断定是对应的key不存在，还是访问缓存发生了异常，所以JetCache针对部分操作提供了另外一套API，提供了完整的返回值 另外主要是提供了tryLock、tryLockAndRun的default实现
AbstractCache
jetcache-core/src/main/java/com/alicp/jetcache/AbstractCache.java
代码语言：javascript复制public abstract class AbstractCache<K, V> implements Cache<K, V> {
private static Logger logger = LoggerFactory.getLogger(AbstractCache.class);
private volatile ConcurrentHashMap<Object, LoaderLock> loaderMap;
protected volatile boolean closed;
//......
@Override
public final CacheGetResult<V> GET(K key) {
long t = System.currentTimeMillis();
CacheGetResult<V> result;
if (key == null) {
result = new CacheGetResult<V>(CacheResultCode.FAIL, CacheResult.MSG_ILLEGAL_ARGUMENT, null);
} else {
result = do_GET(key);
}
result.future().thenRun(() -> {
CacheGetEvent event = new CacheGetEvent(this, System.currentTimeMillis() - t, key, result);
notify(event);
});
return result;
}
protected abstract CacheGetResult<V> do_GET(K key);
@Override
public final MultiGetResult<K, V> GET_ALL(Set<? extends K> keys) {
long t = System.currentTimeMillis();
MultiGetResult<K, V> result;
if (keys == null) {
result = new MultiGetResult<>(CacheResultCode.FAIL, CacheResult.MSG_ILLEGAL_ARGUMENT, null);
} else {
result = do_GET_ALL(keys);
}
result.future().thenRun(() -> {
CacheGetAllEvent event = new CacheGetAllEvent(this, System.currentTimeMillis() - t, keys, result);
notify(event);
});
return result;
}
protected abstract MultiGetResult<K, V> do_GET_ALL(Set<? extends K> keys);
@Override
public final V computeIfAbsent(K key, Function<K, V> loader, boolean cacheNullWhenLoaderReturnNull) {
return computeIfAbsentImpl(key, loader, cacheNullWhenLoaderReturnNull,
0, null, this);
}
@Override
public final V computeIfAbsent(K key, Function<K, V> loader, boolean cacheNullWhenLoaderReturnNull,
long expireAfterWrite, TimeUnit timeUnit) {
return computeIfAbsentImpl(key, loader, cacheNullWhenLoaderReturnNull,
expireAfterWrite, timeUnit, this);
}
@Override
public final CacheResult PUT(K key, V value, long expireAfterWrite, TimeUnit timeUnit) {
long t = System.currentTimeMillis();
CacheResult result;
if (key == null) {
result = CacheResult.FAIL_ILLEGAL_ARGUMENT;
} else {
result = do_PUT(key, value, expireAfterWrite, timeUnit);
}
result.future().thenRun(() -> {
CachePutEvent event = new CachePutEvent(this, System.currentTimeMillis() - t, key, value, result);
notify(event);
});
return result;
}
protected abstract CacheResult do_PUT(K key, V value, long expireAfterWrite, TimeUnit timeUnit);
@Override
public final CacheResult PUT_ALL(Map<? extends K, ? extends V> map, long expireAfterWrite, TimeUnit timeUnit) {
long t = System.currentTimeMillis();
CacheResult result;
if (map == null) {
result = CacheResult.FAIL_ILLEGAL_ARGUMENT;
} else {
result = do_PUT_ALL(map, expireAfterWrite, timeUnit);
}
result.future().thenRun(() -> {
CachePutAllEvent event = new CachePutAllEvent(this, System.currentTimeMillis() - t, map, result);
notify(event);
});
return result;
}
protected abstract CacheResult do_PUT_ALL(Map<? extends K, ? extends V> map, long expireAfterWrite, TimeUnit timeUnit);
@Override
public final CacheResult REMOVE(K key) {
long t = System.currentTimeMillis();
CacheResult result;
if (key == null) {
result = CacheResult.FAIL_ILLEGAL_ARGUMENT;
} else {
result = do_REMOVE(key);
}
result.future().thenRun(() -> {
CacheRemoveEvent event = new CacheRemoveEvent(this, System.currentTimeMillis() - t, key, result);
notify(event);
});
return result;
}
protected abstract CacheResult do_REMOVE(K key);
@Override
public final CacheResult REMOVE_ALL(Set<? extends K> keys) {
long t = System.currentTimeMillis();
CacheResult result;
if (keys == null) {
result = CacheResult.FAIL_ILLEGAL_ARGUMENT;
} else {
result = do_REMOVE_ALL(keys);
}
result.future().thenRun(() -> {
CacheRemoveAllEvent event = new CacheRemoveAllEvent(this, System.currentTimeMillis() - t, keys, result);
notify(event);
});
return result;
}
protected abstract CacheResult do_REMOVE_ALL(Set<? extends K> keys);
@Override
public final CacheResult PUT_IF_ABSENT(K key, V value, long expireAfterWrite, TimeUnit timeUnit) {
long t = System.currentTimeMillis();
CacheResult result;
if (key == null) {
result = CacheResult.FAIL_ILLEGAL_ARGUMENT;
} else {
result = do_PUT_IF_ABSENT(key, value, expireAfterWrite, timeUnit);
}
result.future().thenRun(() -> {
CachePutEvent event = new CachePutEvent(this, System.currentTimeMillis() - t, key, value, result);
notify(event);
});
return result;
}
protected abstract CacheResult do_PUT_IF_ABSENT(K key, V value, long expireAfterWrite, TimeUnit timeUnit);
@Override
public void close() {
this.closed = true;
}
//......
}
AbstractCache主要是实现了Cache的GET、GET_ALL、PUT、PUT_ALL、REMOVE、REMOVE_ALL、PUT_IF_ABSENT、computeIfAbsent、close方法，同时它定义了do_GET、do_GET_ALL、do_PUT、do_PUT_ALL、do_REMOVE、do_REMOVE_ALL、do_PUT_IF_ABSENT抽象方法 它有几个子类，分别是AbstractEmbeddedCache、AbstractExternalCache、MultiLevelCache
AbstractEmbeddedCache
jetcache-core/src/main/java/com/alicp/jetcache/embedded/AbstractEmbeddedCache.java
代码语言：javascript复制public abstract class AbstractEmbeddedCache<K, V> extends AbstractCache<K, V> {
protected EmbeddedCacheConfig<K, V> config;
protected InnerMap innerMap;
protected abstract InnerMap createAreaCache();
public AbstractEmbeddedCache(EmbeddedCacheConfig<K, V> config) {
this.config = config;
innerMap = createAreaCache();
}
@Override
protected CacheGetResult<V> do_GET(K key) {
Object newKey = buildKey(key);
CacheValueHolder<V> holder = (CacheValueHolder<V>) innerMap.getValue(newKey);
return parseHolderResult(holder);
}
@Override
protected MultiGetResult<K, V> do_GET_ALL(Set<? extends K> keys) {
ArrayList<K> keyList = new ArrayList<K>(keys.size());
ArrayList<Object> newKeyList = new ArrayList<Object>(keys.size());
keys.stream().forEach((k) -> {
Object newKey = buildKey(k);
keyList.add(k);
newKeyList.add(newKey);
});
Map<Object, CacheValueHolder<V>> innerResultMap = innerMap.getAllValues(newKeyList);
Map<K, CacheGetResult<V>> resultMap = new HashMap<>();
for (int i = 0; i < keyList.size(); i ) {
K key = keyList.get(i);
Object newKey = newKeyList.get(i);
CacheValueHolder<V> holder = innerResultMap.get(newKey);
resultMap.put(key, parseHolderResult(holder));
}
MultiGetResult<K, V> result = new MultiGetResult<>(CacheResultCode.SUCCESS, null, resultMap);
return result;
}
@Override
protected CacheResult do_PUT(K key, V value, long expireAfterWrite, TimeUnit timeUnit) {
CacheValueHolder<V> cacheObject = new CacheValueHolder(value ,timeUnit.toMillis(expireAfterWrite));
innerMap.putValue(buildKey(key), cacheObject);
return CacheResult.SUCCESS_WITHOUT_MSG;
}
@Override
protected CacheResult do_PUT_ALL(Map<? extends K, ? extends V> map, long expireAfterWrite, TimeUnit timeUnit) {
HashMap newKeyMap = new HashMap();
for (Map.Entry<? extends K, ? extends V> en : map.entrySet()) {
CacheValueHolder<V> cacheObject = new CacheValueHolder(en.getValue(), timeUnit.toMillis(expireAfterWrite));
newKeyMap.put(buildKey(en.getKey()), cacheObject);
}
innerMap.putAllValues(newKeyMap);
final HashMap resultMap = new HashMap();
map.keySet().forEach((k) -> resultMap.put(k, CacheResultCode.SUCCESS));
return CacheResult.SUCCESS_WITHOUT_MSG;
}
//......
}
AbstractEmbeddedCache继承了AbstractCache，它基于InnerMap实现了AbstractCache定义的一系列do_XXX方法，config方法返回的是EmbeddedCacheConfig 它主要有两个实现类，分别是LinkedHashMapCache、CaffeineCache
AbstractExternalCache
jetcache-core/src/main/java/com/alicp/jetcache/external/AbstractExternalCache.java
代码语言：javascript复制public abstract class AbstractExternalCache<K, V> extends AbstractCache<K, V> {
private ExternalCacheConfig<K, V> config;
public AbstractExternalCache(ExternalCacheConfig<K, V> config) {
this.config = config;
checkConfig();
}
protected void checkConfig() {
if (config.getValueEncoder() == null) {
throw new CacheConfigException("no value encoder");
}
if (config.getValueDecoder() == null) {
throw new CacheConfigException("no value decoder");
}
if (config.getKeyPrefix() == null) {
throw new CacheConfigException("keyPrefix is required");
}
}
public byte[] buildKey(K key) {
try {
Object newKey = key;
if (config.getKeyConvertor() != null) {
if (config.getKeyConvertor() instanceof KeyConvertor) {
if (!isPreservedKey(key)) {
// since 2.7.3 KeyConvertor extends Function<Object, Object>
newKey = config.getKeyConvertor().apply(key);
}
} else {
// before 2.7.3, KeyConvertor is interface only place some constants.
// "key convertor" is Function<Object, Object> and can't process byte[] and String
if (key instanceof byte[]) {
newKey = key;
} else if (key instanceof String) {
newKey = key;
} else {
newKey = config.getKeyConvertor().apply(key);
}
}
}
return ExternalKeyUtil.buildKeyAfterConvert(newKey, config.getKeyPrefix());
} catch (IOException e) {
throw new CacheException(e);
}
}
private boolean isPreservedKey(Object key) {
if (key instanceof byte[]) {
byte[] keyBytes = (byte[]) key;
return endWith(keyBytes, RefreshCache.LOCK_KEY_SUFFIX)
|| endWith(keyBytes, RefreshCache.TIMESTAMP_KEY_SUFFIX);
}
return false;
}
private boolean endWith(byte[] key, byte[] suffix) {
int len = suffix.length;
if (key.length < len) {
return false;
}
int startPos = key.length - len;
for (int i = 0; i < len; i ) {
if (key[startPos i] != suffix[i]) {
return false;
}
}
return true;
}
}
AbstractExternalCache继承了AbstractCache，其config方法返回的是ExternalCacheConfig，提供了buildKey方法；它有几个实现类，分别是MockRemoteCache、RedisCache(
jedis实现)、RedisLettuceCache、RedisSpringDataCache、RedissonCache
MultiLevelCache
jetcache-core/src/main/java/com/alicp/jetcache/MultiLevelCache.java
代码语言：javascript复制public class MultiLevelCache<K, V> extends AbstractCache<K, V> {
private Cache[] caches;
private MultiLevelCacheConfig<K, V> config;
@SuppressWarnings("unchecked")
@Deprecated
public MultiLevelCache(Cache... caches) throws CacheConfigException {
this.caches = caches;
checkCaches();
CacheConfig lastConfig = caches[caches.length - 1].config();
config = new MultiLevelCacheConfig<>();
config.setCaches(Arrays.asList(caches));
config.setExpireAfterWriteInMillis(lastConfig.getExpireAfterWriteInMillis());
config.setCacheNullValue(lastConfig.isCacheNullValue());
}
@SuppressWarnings("unchecked")
public MultiLevelCache(MultiLevelCacheConfig<K, V> cacheConfig) throws CacheConfigException {
this.config = cacheConfig;
this.caches = cacheConfig.getCaches().toArray(new Cache[]{});
checkCaches();
}
private void checkCaches() {
if (caches == null || caches.length == 0) {
throw new IllegalArgumentException();
}
for (Cache c : caches) {
if (c.config().getLoader() != null) {
throw new CacheConfigException("Loader on sub cache is not allowed, set the loader into MultiLevelCache.");
}
}
}
public Cache[] caches() {
return caches;
}
@Override
public MultiLevelCacheConfig<K, V> config() {
return config;
}
@Override
public CacheResult PUT(K key, V value) {
if (config.isUseExpireOfSubCache()) {
return PUT(key, value, 0, null);
} else {
return PUT(key, value, config().getExpireAfterWriteInMillis(), TimeUnit.MILLISECONDS);
}
}
@Override
public CacheResult PUT_ALL(Map<? extends K, ? extends V> map) {
if (config.isUseExpireOfSubCache()) {
return PUT_ALL(map, 0, null);
} else {
return PUT_ALL(map, config().getExpireAfterWriteInMillis(), TimeUnit.MILLISECONDS);
}
}
@Override
protected CacheGetResult<V> do_GET(K key) {
for (int i = 0; i < caches.length; i ) {
Cache cache = caches[i];
CacheGetResult result = cache.GET(key);
if (result.isSuccess()) {
CacheValueHolder<V> holder = unwrapHolder(result.getHolder());
checkResultAndFillUpperCache(key, i, holder);
return new CacheGetResult(CacheResultCode.SUCCESS, null, holder);
}
}
return CacheGetResult.NOT_EXISTS_WITHOUT_MSG;
}
private CacheValueHolder<V> unwrapHolder(CacheValueHolder<V> h) {
// if @Cached or @CacheCache change type from REMOTE to BOTH (or from BOTH to REMOTE),
// during the dev/publish process, the value type which different application server put into cache server will be different
// (CacheValueHolder<V> and CacheValueHolder<CacheValueHolder<V>>, respectively).
// So we need correct the problem at here and in CacheGetResult.
Objects.requireNonNull(h);
if (h.getValue() instanceof CacheValueHolder) {
return (CacheValueHolder<V>) h.getValue();
} else {
return h;
}
}
private void checkResultAndFillUpperCache(K key, int i, CacheValueHolder<V> h) {
Objects.requireNonNull(h);
long currentExpire = h.getExpireTime();
long now = System.currentTimeMillis();
if (now <= currentExpire) {
if(config.isUseExpireOfSubCache()){
PUT_caches(i, key, h.getValue(), 0, null);
} else {
long restTtl = currentExpire - now;
if (restTtl > 0) {
PUT_caches(i, key, h.getValue(), restTtl, TimeUnit.MILLISECONDS);
}
}
}
}
@Override
protected MultiGetResult<K, V> do_GET_ALL(Set<? extends K> keys) {
HashMap<K, CacheGetResult<V>> resultMap = new HashMap<>();
Set<K> restKeys = new HashSet<>(keys);
for (int i = 0; i < caches.length; i ) {
if (restKeys.size() == 0) {
break;
}
Cache<K, CacheValueHolder<V>> c = caches[i];
MultiGetResult<K, CacheValueHolder<V>> allResult = c.GET_ALL(restKeys);
if (allResult.isSuccess() && allResult.getValues() != null) {
for (Map.Entry<K, CacheGetResult<CacheValueHolder<V>>> en : allResult.getValues().entrySet()) {
K key = en.getKey();
CacheGetResult result = en.getValue();
if (result.isSuccess()) {
CacheValueHolder<V> holder = unwrapHolder(result.getHolder());
checkResultAndFillUpperCache(key, i, holder);
resultMap.put(key, new CacheGetResult(CacheResultCode.SUCCESS, null, holder));
restKeys.remove(key);
}
}
}
}
for (K k : restKeys) {
resultMap.put(k, CacheGetResult.NOT_EXISTS_WITHOUT_MSG);
}
return new MultiGetResult<>(CacheResultCode.SUCCESS, null, resultMap);
}
@Override
protected CacheResult do_PUT(K key, V value, long expireAfterWrite, TimeUnit timeUnit) {
return PUT_caches(caches.length, key, value, expireAfterWrite, timeUnit);
}
@Override
protected CacheResult do_PUT_ALL(Map<? extends K, ? extends V> map, long expireAfterWrite, TimeUnit timeUnit) {
CompletableFuture<ResultData> future = CompletableFuture.completedFuture(null);
for (Cache c : caches) {
CacheResult r;
if(timeUnit == null) {
r = c.PUT_ALL(map);
} else {
r = c.PUT_ALL(map, expireAfterWrite, timeUnit);
}
future = combine(future, r);
}
return new CacheResult(future);
}
private CacheResult PUT_caches(int lastIndex, K key, V value, long expire, TimeUnit timeUnit) {
CompletableFuture<ResultData> future = CompletableFuture.completedFuture(null);
for (int i = 0; i < lastIndex; i ) {
Cache cache = caches[i];
CacheResult r;
if (timeUnit == null) {
r = cache.PUT(key, value);
} else {
r = cache.PUT(key, value, expire, timeUnit);
}
future = combine(future, r);
}
return new CacheResult(future);
}
private CompletableFuture<ResultData> combine(CompletableFuture<ResultData> future, CacheResult result) {
return future.thenCombine(result.future(), (d1, d2) -> {
if (d1 == null) {
return d2;
}
if (d1.getResultCode() != d2.getResultCode()) {
return new ResultData(CacheResultCode.PART_SUCCESS, null, null);
}
return d1;
});
}
@Override
protected CacheResult do_REMOVE(K key) {
CompletableFuture<ResultData> future = CompletableFuture.completedFuture(null);
for (Cache cache : caches) {
CacheResult r = cache.REMOVE(key);
future = combine(future, r);
}
return new CacheResult(future);
}
@Override
protected CacheResult do_REMOVE_ALL(Set<? extends K> keys) {
CompletableFuture<ResultData> future = CompletableFuture.completedFuture(null);
for (Cache cache : caches) {
CacheResult r = cache.REMOVE_ALL(keys);
future = combine(future, r);
}
return new CacheResult(future);
}
@Override
public <T> T unwrap(Class<T> clazz) {
Objects.requireNonNull(clazz);
for (Cache cache : caches) {
try {
T obj = (T) cache.unwrap(clazz);
if (obj != null) {
return obj;
}
} catch (IllegalArgumentException e) {
// ignore
}
}
throw new IllegalArgumentException(clazz.getName());
}
@Override
public AutoReleaseLock tryLock(K key, long expire, TimeUnit timeUnit) {
if (key == null) {
return null;
}
return caches[caches.length - 1].tryLock(key, expire, timeUnit);
}
@Override
public boolean putIfAbsent(K key, V value) {
throw new UnsupportedOperationException("putIfAbsent is not supported by MultiLevelCache");
}
@Override
protected CacheResult do_PUT_IF_ABSENT(K key, V value, long expireAfterWrite, TimeUnit timeUnit) {
throw new UnsupportedOperationException("PUT_IF_ABSENT is not supported by MultiLevelCache");
}
@Override
public void close() {
super.close();
for (Cache c : caches) {
c.close();
}
}
}
MultiLevelCache继承了AbstractCache，它定义了caches(
Cache[])属性，其config方法返回的是MultiLevelCacheConfig 其do_GET方法遍历caches，执行其GET方法，若result为success，则返回，否则继续遍历下一个cache，若都没有success的则返回CacheGetResult.NOT_EXISTS_WITHOUT_MSG；当result为success的时候会执行checkResultAndFillUpperCache方法，将查询到的值回填到遍历到的index及以下的cache上 其do_PUT方法委托给了PUT_caches，其lastIndex参数为caches.length，它遍历caches挨个更新指定key的值 其do_REMOVE方法遍历caches，挨个执行每个cache的REMOVE方法
示例
代码语言：javascript复制public class MultiLevelCacheExample {
public static void main(String[] args) {
Cache<Object, Object> l1Cache = CaffeineCacheBuilder.createCaffeineCacheBuilder()
.limit(100)
.expireAfterWrite(200, TimeUnit.SECONDS)
.keyConvertor(Fastjson2KeyConvertor.INSTANCE)
.buildCache();
GenericObjectPoolConfig pc = new GenericObjectPoolConfig();
pc.setMinIdle(2);
pc.setMaxIdle(10);
pc.setMaxTotal(10);
JedisPool pool = new JedisPool(pc, "127.0.0.1", 6379);
Cache<Object, Object> l2Cache = RedisCacheBuilder.createRedisCacheBuilder()
.jedisPool(pool)
.keyPrefix("projectD")
.expireAfterWrite(200, TimeUnit.SECONDS)
.keyConvertor(Fastjson2KeyConvertor.INSTANCE)
.valueEncoder(JavaValueEncoder.INSTANCE)
.valueDecoder(JavaValueDecoder.INSTANCE)
.buildCache();
Cache<Object, Object> multiLevelCache = MultiLevelCacheBuilder.createMultiLevelCacheBuilder()
.addCache(l1Cache, l2Cache)
.buildCache();
multiLevelCache.put("K1", "V1");
multiLevelCache.put("K2", "V2", 20, TimeUnit.SECONDS);
System.out.println(multiLevelCache.get("K1"));
multiLevelCache.remove("K2");
}
}
小结
- Cache接口主要是定义了大写的GET、GET_ALL、PUT、PUT_ALL、REMOVE、REMOVE_ALL、PUT_IF_ABSENT方法，以及基于这些大写方法包装的小写default方法；
- AbstractCache主要是实现了Cache的GET、GET_ALL、PUT、PUT_ALL、REMOVE、REMOVE_ALL、PUT_IF_ABSENT、computeIfAbsent、close方法，同时它定义了do_GET、do_GET_ALL、do_PUT、do_PUT_ALL、do_REMOVE、do_REMOVE_ALL、do_PUT_IF_ABSENT抽象方法；它有几个子类，分别是AbstractEmbeddedCache、AbstractExternalCache、MultiLevelCache
- MultiLevelCache继承了AbstractCache，它定义了caches(
Cache[])属性，其config方法返回的是MultiLevelCacheConfig；其do_GET方法遍历caches，执行其GET方法，若result为success，则返回，否则继续遍历下一个cache，若都没有success的则返回CacheGetResult.NOT_EXISTS_WITHOUT_MSG；当result为success的时候会执行checkResultAndFillUpperCache方法，将查询到的值回填到遍历到的index及以下的cache上；其do_PUT方法委托给了PUT_caches，其lastIndex参数为caches.length，它遍历caches挨个更新指定key的值；其do_REMOVE方法遍历caches，挨个执行每个cache的REMOVE方法
