* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
- */
+ */
package org.wamblee.cache;
import org.apache.log4j.Logger;
/**
- * Represents a cached object. The object is either retrieved from the cache if the cache
- * has it, or a call back is invoked to get the object (and put it in the cache).
+ * Represents a cached object. The object is either retrieved from the cache if
+ * the cache has it, or a call back is invoked to get the object (and put it in
+ * the cache).
*/
public class CachedObject<KeyType extends Serializable, ValueType extends Serializable> {
-
+
private static final Logger LOGGER = Logger.getLogger(CachedObject.class);
-
+
/**
- * Callback invoked to compute an object if it was not found in the cache.
- * @param <T> Type of the object
+ * Callback invoked to compute an object if it was not found in the cache.
+ *
+ * @param <T>
+ * Type of the object
*/
public static interface Computation<Key extends Serializable, Value extends Serializable> {
/**
- * Gets the object. Called when the object is not in the cache.
- * @param aObjectKey Id of the object in the cache.
- * @return Object, must be non-null.
+ * Gets the object. Called when the object is not in the cache.
+ *
+ * @param aObjectKey
+ * Id of the object in the cache.
+ * @return Object, must be non-null.
*/
- Value getObject(Key aObjectKey);
+ Value getObject(Key aObjectKey);
}
-
+
/**
- * Cache to use.
+ * Cache to use.
*/
private Cache<KeyType, ValueType> _cache;
-
+
/**
- * Key of the object in the cache.
+ * Key of the object in the cache.
*/
- private KeyType _objectKey;
-
+ private KeyType _objectKey;
+
/**
- * Computation used to obtain the object if it is not found in the cache.
+ * Computation used to obtain the object if it is not found in the cache.
*/
- private Computation<KeyType, ValueType> _computation;
-
+ private Computation<KeyType, ValueType> _computation;
+
/**
- * Constructs the cached object.
- * @param aCache Cache to use.
- * @param aObjectKey Key of the object in the cache.
- * @param aComputation Computation to get the object in case the object is not in the cache.
+ * Constructs the cached object.
+ *
+ * @param aCache
+ * Cache to use.
+ * @param aObjectKey
+ * Key of the object in the cache.
+ * @param aComputation
+ * Computation to get the object in case the object is not in the
+ * cache.
*/
- public CachedObject(Cache<KeyType,ValueType> aCache, KeyType aObjectKey, Computation<KeyType,ValueType> aComputation) {
- _cache = aCache;
- _objectKey = aObjectKey;
- _computation = aComputation;
+ public CachedObject(Cache<KeyType, ValueType> aCache, KeyType aObjectKey,
+ Computation<KeyType, ValueType> aComputation) {
+ _cache = aCache;
+ _objectKey = aObjectKey;
+ _computation = aComputation;
}
-
+
/**
- * Gets the object. Since the object is cached, different calls to this method may return
- * different objects.
- * @return Object.
+ * Gets the object. Since the object is cached, different calls to this
+ * method may return different objects.
+ *
+ * @return Object.
*/
- public ValueType get() {
- ValueType object = (ValueType)_cache.get(_objectKey); // the used cache is thread safe.
- if ( object == null ) {
- // synchronize the computation to make sure that the object is only computed
- // once when multiple concurrent threads detect that the entry must be
- // recomputed.
- synchronized (this) {
- object = (ValueType)_cache.get(_objectKey);
- if ( object == null ) {
- // No other thread did a recomputation so we must do this now.
- LOGGER.debug("Refreshing cache for '" + _objectKey + "'");
- object = _computation.getObject(_objectKey);
- _cache.put(_objectKey, object);
- }
+ public ValueType get() {
+ ValueType object = (ValueType) _cache.get(_objectKey); // the used
+ // cache is
+ // thread safe.
+ if (object == null) {
+ // synchronize the computation to make sure that the object is only
+ // computed
+ // once when multiple concurrent threads detect that the entry must
+ // be
+ // recomputed.
+ synchronized (this) {
+ object = (ValueType) _cache.get(_objectKey);
+ if (object == null) {
+ // No other thread did a recomputation so we must do this
+ // now.
+ LOGGER.debug("Refreshing cache for '" + _objectKey + "'");
+ object = _computation.getObject(_objectKey);
+ _cache.put(_objectKey, object);
+ }
}
}
- return object;
+ return object;
}
-
+
/**
- * Invalidates the cache for the object so that it is recomputed the next
- * time it is requested.
- *
+ * Invalidates the cache for the object so that it is recomputed the next
+ * time it is requested.
+ *
*/
- public void invalidate() {
+ public void invalidate() {
_cache.remove(_objectKey);
}
-
+
/**
- * Gets the cache.
- * @return Cache.
+ * Gets the cache.
+ *
+ * @return Cache.
*/
- public Cache getCache() {
- return _cache;
+ public Cache getCache() {
+ return _cache;
}
}
git://wamblee.org / utils / blobdiff