/*
- * Copyright 2005 the original author or authors.
+ * Copyright 2005-2010 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* 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 java.io.Serializable;
-
import org.apache.log4j.Logger;
+import java.io.Serializable;
+
/**
* 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).
- *
+ *
* @author Erik Brakkee
+ *
*/
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
- */
- 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.
- */
- Value getObject(Key aObjectKey);
- }
-
/**
* Cache to use.
*/
- private Cache<KeyType, ValueType> _cache;
+ private Cache<KeyType, ValueType> 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.
*/
- private Computation<KeyType, ValueType> _computation;
+ private Computation<KeyType, ValueType> computation;
/**
* Constructs the cached object.
* cache.
*/
public CachedObject(Cache<KeyType, ValueType> aCache, KeyType aObjectKey,
- Computation<KeyType, ValueType> aComputation) {
- _cache = aCache;
- _objectKey = aObjectKey;
- _computation = aComputation;
+ Computation<KeyType, ValueType> aComputation) {
+ cache = aCache;
+ objectKey = aObjectKey;
+ computation = aComputation;
}
/**
* @return Object.
*/
public ValueType get() {
- ValueType object = (ValueType) _cache.get(_objectKey); // the used
- // cache is
- // thread safe.
+ 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
// be
// recomputed.
synchronized (this) {
- object = (ValueType) _cache.get(_objectKey);
+ 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);
+ LOGGER.debug("Refreshing cache for '" + objectKey + "'");
+ object = computation.getObject(objectKey);
+ cache.put(objectKey, object);
}
}
}
+
return object;
}
/**
* Invalidates the cache for the object so that it is recomputed the next
* time it is requested.
- *
*/
public void invalidate() {
- _cache.remove(_objectKey);
+ cache.remove(objectKey);
}
/**
* @return Cache.
*/
public Cache getCache() {
- return _cache;
+ return cache;
+ }
+
+ /**
+ * 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.
+ */
+ Value getObject(Key aObjectKey);
}
}