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fixed CachingMapDecorator to support garbage-collected weak references (again)

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This commit is contained in:
Juergen Hoeller
2009-03-23 11:34:51 +00:00
parent 84cc32525f
commit 4708446d4a
2 changed files with 108 additions and 44 deletions
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78
org.springframework.core/src/main/java/org/springframework/util/CachingMapDecorator.java
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@@ -22,6 +22,7 @@ import java.lang.ref.WeakReference;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.LinkedList;
@@ -33,7 +34,7 @@ import java.util.WeakHashMap;
* A simple decorator for a Map, encapsulating the workflow for caching
* expensive values in a target Map. Supports caching weak or strong keys.
*
* <p>This class is also an abstract template. Caching Map implementations
* <p>This class is an abstract template. Caching Map implementations
* should subclass and override the <code>create(key)</code> method which
* encapsulates expensive creation of a new object.
*
@@ -41,9 +42,9 @@ import java.util.WeakHashMap;
* @author Juergen Hoeller
* @since 1.2.2
*/
public class CachingMapDecorator<K, V> implements Map<K, V>, Serializable {
public abstract class CachingMapDecorator<K, V> implements Map<K, V>, Serializable {
protected static Object NULL_VALUE = new Object();
private static Object NULL_VALUE = new Object();
private final Map<K, Object> targetMap;
@@ -150,7 +151,16 @@ public class CachingMapDecorator<K, V> implements Map<K, V>, Serializable {
}
public V remove(Object key) {
return unwrapIfNecessary(this.targetMap.remove(key));
return unwrapReturnValue(this.targetMap.remove(key));
}
@SuppressWarnings("unchecked")
private V unwrapReturnValue(Object value) {
Object returnValue = value;
if (returnValue instanceof Reference) {
returnValue = ((Reference) returnValue).get();
}
return (returnValue == NULL_VALUE ? null : (V) returnValue);
}
public void putAll(Map<? extends K, ? extends V> map) {
@@ -186,8 +196,16 @@ public class CachingMapDecorator<K, V> implements Map<K, V>, Serializable {
@SuppressWarnings("unchecked")
private Collection<V> valuesCopy() {
LinkedList<V> values = new LinkedList<V>();
for (Object value : this.targetMap.values()) {
values.add(value instanceof Reference ? ((Reference<V>) value).get() : (V) value);
for (Iterator<Object> it = this.targetMap.values().iterator(); it.hasNext();) {
Object value = it.next();
if (value instanceof Reference) {
value = ((Reference) value).get();
if (value == null) {
it.remove();
continue;
}
}
values.add(value == NULL_VALUE ? null : (V) value);
}
return values;
}
@@ -203,10 +221,20 @@ public class CachingMapDecorator<K, V> implements Map<K, V>, Serializable {
}
}
@SuppressWarnings("unchecked")
private Set<Map.Entry<K, V>> entryCopy() {
Map<K,V> entries = new LinkedHashMap<K, V>();
for (Entry<K, Object> entry : this.targetMap.entrySet()) {
entries.put(entry.getKey(), unwrapIfNecessary(entry.getValue()));
for (Iterator<Entry<K, Object>> it = this.targetMap.entrySet().iterator(); it.hasNext();) {
Entry<K, Object> entry = it.next();
Object value = entry.getValue();
if (value instanceof Reference) {
value = ((Reference) value).get();
if (value == null) {
it.remove();
continue;
}
}
entries.put(entry.getKey(), value == NULL_VALUE ? null : (V) value);
}
return entries.entrySet();
}
@@ -223,13 +251,13 @@ public class CachingMapDecorator<K, V> implements Map<K, V>, Serializable {
newValue = NULL_VALUE;
}
else if (useWeakValue(key, value)) {
newValue = new WeakReference<V>(value);
newValue = new WeakReference<Object>(newValue);
}
return unwrapIfNecessary(this.targetMap.put(key, newValue));
return unwrapReturnValue(this.targetMap.put(key, newValue));
}
/**
* Decide whether use a weak reference for the value of
* Decide whether to use a weak reference for the value of
* the given key-value pair.
* @param key the candidate key
* @param value the candidate value
@@ -252,27 +280,15 @@ public class CachingMapDecorator<K, V> implements Map<K, V>, Serializable {
@SuppressWarnings("unchecked")
public V get(Object key) {
Object value = this.targetMap.get(key);
if (value == null) {
V newVal = create((K) key);
if (newVal != null) {
put((K) key, newVal);
}
return newVal;
}
return unwrapIfNecessary(value);
}
@SuppressWarnings("unchecked")
private V unwrapIfNecessary(Object value) {
if (value instanceof Reference) {
return ((Reference<V>) value).get();
value = ((Reference) value).get();
}
else if (value != null) {
return (V) value;
}
else {
return null;
if (value == null) {
V newValue = create((K) key);
put((K) key, newValue);
return newValue;
}
return (value == NULL_VALUE ? null : (V) value);
}
/**
@@ -281,9 +297,7 @@ public class CachingMapDecorator<K, V> implements Map<K, V>, Serializable {
* @param key the cache key
* @see #get(Object)
*/
protected V create(K key) {
return null;
}
protected abstract V create(K key);
@Override