/*
- * 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.
*/
* cache.
*/
public CachedObject(Cache<KeyType, ValueType> aCache, KeyType aObjectKey,
- Computation<KeyType, ValueType> aComputation) {
+ Computation<KeyType, ValueType> aComputation) {
cache = aCache;
objectKey = aObjectKey;
computation = aComputation;
*/
public ValueType get() {
ValueType object = (ValueType) cache.get(objectKey); // the used
- // cache is
- // thread safe.
+ // cache is
+ // thread safe.
+
if (object == null) {
// synchronize the computation to make sure that the object is only
// computed
// recomputed.
synchronized (this) {
object = (ValueType) cache.get(objectKey);
+
if (object == null) {
// No other thread did a recomputation so we must do this
// now.
}
}
}
+
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);
public Cache getCache() {
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);
+ }
}