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Posted to commits@camel.apache.org by nf...@apache.org on 2023/10/31 13:47:12 UTC
(camel) 01/01: CAMEL-20039: camel-core - SimpleLRUCache add support for soft cache
This is an automated email from the ASF dual-hosted git repository.
nfilotto pushed a commit to branch CAMEL-20039/add-soft-lru-cache
in repository https://gitbox.apache.org/repos/asf/camel.git
commit f05b19a48504e722530aa08f9f52243cc648a476
Author: Nicolas Filotto <nf...@talend.com>
AuthorDate: Tue Oct 31 14:46:16 2023 +0100
CAMEL-20039: camel-core - SimpleLRUCache add support for soft cache
---
.../SimpleLRUCacheTest.java} | 10 +-
.../camel/support/cache/SimpleSoftCacheTest.java | 296 ++++++++++++++++
.../camel/support/DefaultLRUCacheFactory.java | 330 ++----------------
.../apache/camel/support/cache/SimpleLRUCache.java | 289 +++++++++++++++
.../camel/support/cache/SimpleSoftCache.java | 388 +++++++++++++++++++++
5 files changed, 1015 insertions(+), 298 deletions(-)
diff --git a/core/camel-core/src/test/java/org/apache/camel/support/DefaultLRUCacheFactoryTest.java b/core/camel-core/src/test/java/org/apache/camel/support/cache/SimpleLRUCacheTest.java
similarity index 96%
rename from core/camel-core/src/test/java/org/apache/camel/support/DefaultLRUCacheFactoryTest.java
rename to core/camel-core/src/test/java/org/apache/camel/support/cache/SimpleLRUCacheTest.java
index c9f7fdda9b4..d7e9f4549a5 100644
--- a/core/camel-core/src/test/java/org/apache/camel/support/DefaultLRUCacheFactoryTest.java
+++ b/core/camel-core/src/test/java/org/apache/camel/support/cache/SimpleLRUCacheTest.java
@@ -14,7 +14,7 @@
* See the License for the specific language governing permissions and
* limitations under the License.
*/
-package org.apache.camel.support;
+package org.apache.camel.support.cache;
import java.util.ArrayList;
import java.util.List;
@@ -29,14 +29,12 @@ import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTrue;
/**
- * The test class for {@link DefaultLRUCacheFactory}.
+ * The test class for {@link SimpleLRUCache}.
*/
-class DefaultLRUCacheFactoryTest {
+class SimpleLRUCacheTest {
private final List<String> consumed = new ArrayList<>();
- private final DefaultLRUCacheFactory.SimpleLRUCache<String, String> map
- = (DefaultLRUCacheFactory.SimpleLRUCache<String, String>) new DefaultLRUCacheFactory().<String,
- String> createLRUCache(3, consumed::add);
+ private final SimpleLRUCache<String, String> map = new SimpleLRUCache<>(16, 3, consumed::add);
@Test
void forbiddenOperations() {
diff --git a/core/camel-core/src/test/java/org/apache/camel/support/cache/SimpleSoftCacheTest.java b/core/camel-core/src/test/java/org/apache/camel/support/cache/SimpleSoftCacheTest.java
new file mode 100644
index 00000000000..823a36bff7c
--- /dev/null
+++ b/core/camel-core/src/test/java/org/apache/camel/support/cache/SimpleSoftCacheTest.java
@@ -0,0 +1,296 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * 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.apache.camel.support.cache;
+
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * The test class for {@link SimpleSoftCache}.
+ */
+class SimpleSoftCacheTest {
+
+ private final SimpleSoftCache<Integer, Object> cache = new SimpleSoftCache<>(new ConcurrentHashMap<>());
+
+ @Test
+ void testSoftCacheGetAndPut() {
+
+ cache.put(1, "foo");
+ cache.put(2, "bar");
+
+ assertEquals("foo", cache.get(1));
+ assertEquals("bar", cache.get(2));
+ assertNull(cache.get(3));
+
+ assertEquals(2, cache.size());
+ }
+
+ @Test
+ void testSoftCacheContainsValue() {
+ cache.put(1, "foo");
+
+ assertTrue(cache.containsValue("foo"));
+ assertFalse(cache.containsValue("bar"));
+ }
+
+ @Test
+ void testSoftCacheForEach() {
+ cache.put(1, "foo");
+ cache.put(2, "bar");
+
+ Map<Integer, Object> tmp = new HashMap<>();
+ cache.forEach(tmp::put);
+
+ assertEquals("foo", tmp.get(1));
+ assertEquals("bar", tmp.get(2));
+ assertNull(tmp.get(3));
+
+ assertEquals(2, tmp.size());
+ }
+
+ @Test
+ void testSoftCacheReplaceAll() {
+ cache.put(1, "foo");
+ cache.put(2, "bar");
+
+ cache.replaceAll((k, v) -> v + "2");
+
+ assertEquals("foo2", cache.get(1));
+ assertEquals("bar2", cache.get(2));
+
+ assertEquals(2, cache.size());
+ }
+
+ @Test
+ void testSoftCachePutIfAbsent() {
+ cache.put(1, "foo");
+
+ assertEquals("foo", cache.putIfAbsent(1, "bar"));
+ assertEquals("foo", cache.get(1));
+
+ assertNull(cache.putIfAbsent(2, "bar"));
+ assertEquals("bar", cache.get(2));
+ }
+
+ @Test
+ void testSoftCacheRemove() {
+ cache.put(1, "foo");
+ assertFalse(cache.remove(2, "foo"));
+ assertFalse(cache.remove(1, "bar"));
+ assertEquals("foo", cache.get(1));
+ assertFalse(cache.isEmpty());
+ assertTrue(cache.remove(1, "foo"));
+ assertNull(cache.get(1));
+ assertTrue(cache.isEmpty());
+ }
+
+ @Test
+ void testSoftCacheReplaceSpecific() {
+ cache.put(1, "foo");
+ assertFalse(cache.replace(2, "foo", "bar"));
+ assertFalse(cache.replace(1, "bar", "foo"));
+ assertEquals("foo", cache.get(1));
+ assertTrue(cache.replace(1, "foo", "bar"));
+ assertEquals("bar", cache.get(1));
+ }
+
+ @Test
+ void testSoftCacheReplace() {
+ cache.put(1, "foo");
+ assertNull(cache.replace(2, "bar"));
+ assertEquals("foo", cache.get(1));
+ assertEquals("foo", cache.replace(1, "bar"));
+ assertEquals("bar", cache.get(1));
+ }
+
+ @Test
+ void testSoftCacheComputeIfAbsent() {
+ cache.put(1, "foo");
+ assertEquals("foo", cache.computeIfAbsent(1, k -> "bar"));
+ assertEquals("foo", cache.get(1));
+ assertEquals("bar", cache.computeIfAbsent(2, k -> "bar"));
+ assertEquals("bar", cache.get(2));
+ }
+
+ @Test
+ void testSoftCacheComputeIfPresent() {
+ cache.put(1, "foo");
+ assertEquals("bar", cache.computeIfPresent(1, (k, v) -> "bar"));
+ assertEquals("bar", cache.get(1));
+ assertNull(cache.computeIfPresent(1, (k, v) -> null));
+ assertNull(cache.get(1));
+ assertNull(cache.computeIfPresent(1, (k, v) -> "bar"));
+ }
+
+ @Test
+ void testSoftCacheCompute() {
+ cache.put(1, "foo");
+ assertEquals("bar", cache.compute(1, (k, v) -> "bar"));
+ assertEquals("bar", cache.get(1));
+ assertNull(cache.compute(1, (k, v) -> null));
+ assertNull(cache.get(1));
+ assertEquals("bar", cache.compute(1, (k, v) -> "bar"));
+ assertEquals("bar", cache.get(1));
+ assertNull(cache.compute(2, (k, v) -> null));
+ assertNull(cache.get(2));
+ }
+
+ @Test
+ void testSoftCacheMerge() {
+ cache.put(1, "foo");
+ assertEquals("foo-2", cache.merge(1, "2", (v1, v2) -> v1 + "-" + v2));
+ assertEquals("foo-2", cache.get(1));
+ assertNull(cache.merge(1, "2", (v1, v2) -> null));
+ assertNull(cache.get(1));
+ assertEquals("2", cache.merge(1, "2", (v1, v2) -> "bar"));
+ assertEquals("2", cache.get(1));
+ assertEquals("2", cache.merge(2, "2", (v1, v2) -> null));
+ assertEquals("2", cache.get(2));
+ }
+
+ @Test
+ void testSimpleSoftCachePutOverride() {
+ Object old = cache.put(1, "foo");
+ assertNull(old);
+ old = cache.put(2, "bar");
+ assertNull(old);
+
+ assertEquals("foo", cache.get(1));
+ assertEquals("bar", cache.get(2));
+
+ old = cache.put(1, "changed");
+ assertEquals("foo", old);
+ assertEquals("changed", cache.get(1));
+
+ assertEquals(2, cache.size());
+ }
+
+ @Test
+ void testSimpleSoftCachePutAll() {
+ Map<Integer, Object> map = new HashMap<>();
+ map.put(1, "foo");
+ map.put(2, "bar");
+
+ cache.putAll(map);
+
+ assertEquals("foo", cache.get(1));
+ assertEquals("bar", cache.get(2));
+ assertNull(cache.get(3));
+ assertEquals(2, cache.size());
+ }
+
+ @Test
+ void testSimpleSoftCacheRemove() {
+ cache.put(1, "foo");
+ cache.put(2, "bar");
+
+ assertEquals("bar", cache.get(2));
+ cache.remove(2);
+ assertNull(cache.get(2));
+ }
+
+ @Test
+ void testSimpleSoftCacheValues() {
+ cache.put(1, "foo");
+ cache.put(2, "bar");
+
+ Collection<Object> col = cache.values();
+ assertEquals(2, col.size());
+
+ Iterator<Object> it = col.iterator();
+ assertEquals("foo", it.next());
+ assertEquals("bar", it.next());
+ }
+
+ @Test
+ void testSimpleSoftCacheEmpty() {
+ assertTrue(cache.isEmpty());
+
+ cache.put(1, "foo");
+ assertFalse(cache.isEmpty());
+
+ cache.put(2, "bar");
+ assertFalse(cache.isEmpty());
+
+ cache.remove(2);
+ assertFalse(cache.isEmpty());
+
+ cache.clear();
+ assertTrue(cache.isEmpty());
+
+ }
+
+ @Test
+ void testSimpleSoftCacheContainsKey() {
+ assertFalse(cache.containsKey(1));
+ cache.put(1, "foo");
+ assertTrue(cache.containsKey(1));
+
+ assertFalse(cache.containsKey(2));
+ cache.put(2, "foo");
+ assertTrue(cache.containsKey(2));
+ }
+
+ @Test
+ void testSimpleSoftCacheKeySet() {
+ cache.put(1, "foo");
+ cache.put(2, "foo");
+
+ Set<Integer> keys = cache.keySet();
+ assertEquals(2, keys.size());
+
+ Iterator<Integer> it = keys.iterator();
+ assertEquals(1, it.next().intValue());
+ assertEquals(2, it.next().intValue());
+ }
+
+ @Test
+ void testSimpleSoftCacheNotRunOutOfMemory() {
+ // we should not run out of memory using the soft cache
+ // if you run this test with a regular cache then you will run out of memory
+ int maximumCacheSize = 1024;
+ for (int i = 0; i < maximumCacheSize; i++) {
+ Object data = new LargeObject();
+ Integer key = Integer.valueOf(i);
+ cache.put(key, data);
+ }
+
+ Map<Integer, Object> tmp = new HashMap<>(cache);
+ int size = tmp.size();
+ assertTrue(size < maximumCacheSize, "Cache size should not be max, was: " + size);
+ }
+
+ public static class LargeObject {
+
+ byte[] data;
+
+ public LargeObject() {
+ this.data = new byte[100 * 1024 * 1024]; // 100 MB
+ }
+ }
+}
diff --git a/core/camel-support/src/main/java/org/apache/camel/support/DefaultLRUCacheFactory.java b/core/camel-support/src/main/java/org/apache/camel/support/DefaultLRUCacheFactory.java
index d5a21b23d1b..f42d3cf1726 100644
--- a/core/camel-support/src/main/java/org/apache/camel/support/DefaultLRUCacheFactory.java
+++ b/core/camel-support/src/main/java/org/apache/camel/support/DefaultLRUCacheFactory.java
@@ -16,20 +16,13 @@
*/
package org.apache.camel.support;
-import java.util.Collections;
+import java.lang.ref.SoftReference;
import java.util.LinkedHashMap;
import java.util.Map;
-import java.util.Objects;
-import java.util.Queue;
-import java.util.Set;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentLinkedQueue;
-import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.concurrent.atomic.LongAdder;
-import java.util.function.BiFunction;
import java.util.function.Consumer;
-import java.util.function.Function;
+import org.apache.camel.support.cache.SimpleLRUCache;
+import org.apache.camel.support.cache.SimpleSoftCache;
import org.apache.camel.support.service.ServiceHelper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
@@ -49,8 +42,7 @@ public class DefaultLRUCacheFactory extends LRUCacheFactory {
*/
@Override
public <K, V> Map<K, V> createLRUCache(int maximumCacheSize) {
- LOG.trace("Creating LRUCache with maximumCacheSize: {}", maximumCacheSize);
- return new SimpleLRUCache<>(maximumCacheSize);
+ return createLRUCache(16, maximumCacheSize);
}
/**
@@ -61,7 +53,7 @@ public class DefaultLRUCacheFactory extends LRUCacheFactory {
*/
@Override
public <K, V> Map<K, V> createLRUCache(int maximumCacheSize, Consumer<V> onEvict) {
- LOG.trace("Creating LRUCache with maximumCacheSize: {}", maximumCacheSize);
+ LOG.trace("Creating LRUCache with initialCapacity: {}, maximumCacheSize: {}, with onEvict", 16, maximumCacheSize);
return new SimpleLRUCache<>(16, maximumCacheSize, onEvict);
}
@@ -75,8 +67,7 @@ public class DefaultLRUCacheFactory extends LRUCacheFactory {
*/
@Override
public <K, V> Map<K, V> createLRUCache(int initialCapacity, int maximumCacheSize) {
- LOG.trace("Creating LRUCache with initialCapacity: {}, maximumCacheSize: {}", initialCapacity, maximumCacheSize);
- return new SimpleLRUCache<>(initialCapacity, maximumCacheSize);
+ return createLRUCache(initialCapacity, maximumCacheSize, maximumCacheSize > 0);
}
/**
@@ -92,7 +83,9 @@ public class DefaultLRUCacheFactory extends LRUCacheFactory {
public <K, V> Map<K, V> createLRUCache(int initialCapacity, int maximumCacheSize, boolean stopOnEviction) {
LOG.trace("Creating LRUCache with initialCapacity: {}, maximumCacheSize: {}, stopOnEviction: {}", initialCapacity,
maximumCacheSize, stopOnEviction);
- return new SimpleLRUCache<>(initialCapacity, maximumCacheSize, stopOnEviction);
+ return new SimpleLRUCache<K, V>(
+ initialCapacity, maximumCacheSize,
+ stopOnEviction ? DefaultLRUCacheFactory.this::doStop : DefaultLRUCacheFactory.this::doNothing);
}
/**
@@ -104,21 +97,36 @@ public class DefaultLRUCacheFactory extends LRUCacheFactory {
*/
@Override
public <K, V> Map<K, V> createLRUSoftCache(int maximumCacheSize) {
- LOG.trace("Creating LRUSoftCache with maximumCacheSize: {}", maximumCacheSize);
- return new SimpleLRUCache<>(maximumCacheSize);
+ return createLRUSoftCache(16, maximumCacheSize);
}
@Override
public <K, V> Map<K, V> createLRUSoftCache(int initialCapacity, int maximumCacheSize) {
- LOG.trace("Creating LRUCache with initialCapacity: {}, maximumCacheSize: {}", initialCapacity, maximumCacheSize);
- return new SimpleLRUCache<>(initialCapacity, maximumCacheSize);
+ return createLRUSoftCache(initialCapacity, maximumCacheSize, maximumCacheSize > 0);
}
@Override
public <K, V> Map<K, V> createLRUSoftCache(int initialCapacity, int maximumCacheSize, boolean stopOnEviction) {
- LOG.trace("Creating LRUCache with initialCapacity: {}, maximumCacheSize: {}, stopOnEviction: {}", initialCapacity,
+ LOG.trace("Creating LRUSoftCache with initialCapacity: {}, maximumCacheSize: {}, stopOnEviction: {}", initialCapacity,
maximumCacheSize, stopOnEviction);
- return new SimpleLRUCache<>(initialCapacity, maximumCacheSize, stopOnEviction);
+ return new SimpleSoftCache<>(
+ new SimpleLRUCache<K, SoftReference<V>>(
+ initialCapacity, maximumCacheSize,
+ asSoftReferenceConsumer(stopOnEviction
+ ? DefaultLRUCacheFactory.this::doStop : DefaultLRUCacheFactory.this::doNothing)));
+ }
+
+ /**
+ * Converts a consumer of values of type {@code V} into a consumer of referent of {@code SoftReference} of type
+ * {@code V}.
+ */
+ private static <V> Consumer<SoftReference<V>> asSoftReferenceConsumer(Consumer<V> evicted) {
+ return ref -> {
+ V v = ref.get();
+ if (v != null) {
+ evicted.accept(v);
+ }
+ };
}
/**
@@ -131,287 +139,25 @@ public class DefaultLRUCacheFactory extends LRUCacheFactory {
@Override
@Deprecated
public <K, V> Map<K, V> createLRUWeakCache(int maximumCacheSize) {
- LOG.trace("Creating LRUWeakCache with maximumCacheSize: {}", maximumCacheSize);
- return new SimpleLRUCache<>(maximumCacheSize);
+ return createLRUWeakCache(16, maximumCacheSize);
}
@Override
@Deprecated
public <K, V> Map<K, V> createLRUWeakCache(int initialCapacity, int maximumCacheSize) {
- LOG.trace("Creating LRUCache with initialCapacity: {}, maximumCacheSize: {}", initialCapacity, maximumCacheSize);
- return new SimpleLRUCache<>(initialCapacity, maximumCacheSize);
+ return createLRUWeakCache(initialCapacity, maximumCacheSize, maximumCacheSize > 0);
}
@Override
@Deprecated
public <K, V> Map<K, V> createLRUWeakCache(int initialCapacity, int maximumCacheSize, boolean stopOnEviction) {
- LOG.trace("Creating LRUCache with initialCapacity: {}, maximumCacheSize: {}, stopOnEviction: {}", initialCapacity,
+ LOG.trace("Creating LRUWeakCache with initialCapacity: {}, maximumCacheSize: {}, stopOnEviction: {}", initialCapacity,
maximumCacheSize, stopOnEviction);
- return new SimpleLRUCache<>(initialCapacity, maximumCacheSize, stopOnEviction);
- }
-
- class SimpleLRUCache<K, V> extends ConcurrentHashMap<K, V> {
-
- static final float DEFAULT_LOAD_FACTOR = 0.75f;
- /**
- * The flag indicating that an eviction process is in progress.
- */
- private final AtomicBoolean eviction = new AtomicBoolean();
- /**
- * The maximum cache size.
- */
- private final int maximumCacheSize;
- /**
- * The last changes recorded.
- */
- private final Queue<Entry<K, V>> lastChanges = new ConcurrentLinkedQueue<>();
- /**
- * The total amount of changes recorded.
- */
- private final LongAdder totalChanges = new LongAdder();
- /**
- * The function to call when an entry is evicted.
- */
- private final Consumer<V> evict;
-
- public SimpleLRUCache(int maximumCacheSize) {
- this(16, maximumCacheSize, maximumCacheSize > 0);
- }
-
- public SimpleLRUCache(int initialCapacity, int maximumCacheSize) {
- this(initialCapacity, maximumCacheSize, maximumCacheSize > 0);
- }
-
- public SimpleLRUCache(int initialCapacity, int maximumCacheSize, boolean stopOnEviction) {
- this(initialCapacity, maximumCacheSize,
- stopOnEviction ? DefaultLRUCacheFactory.this::doStop : DefaultLRUCacheFactory.this::doNothing);
- }
-
- public SimpleLRUCache(int initialCapacity, int maximumCacheSize, Consumer<V> evicted) {
- super(initialCapacity, DEFAULT_LOAD_FACTOR);
- this.maximumCacheSize = maximumCacheSize;
- this.evict = Objects.requireNonNull(evicted);
- }
-
- /**
- * Adds a new change in case the mapping function doesn't return {@code null}.
- *
- * @param context the context of the write operation
- * @param mappingFunction the mapping function to apply.
- * @return the result of the mapping function.
- */
- private V addChange(OperationContext<K, V> context, Function<? super K, ? extends V> mappingFunction) {
- K key = context.key;
- V value = mappingFunction.apply(key);
- if (value == null) {
- return null;
- }
- lastChanges.add(Map.entry(key, value));
- totalChanges.increment();
- return value;
- }
-
- @Override
- public V put(K key, V value) {
- if (key == null || value == null) {
- throw new NullPointerException();
- }
- try (OperationContext<K, V> context = new OperationContext<>(this, key)) {
- super.compute(
- key,
- (k, v) -> {
- context.result = v;
- return addChange(context, x -> value);
- });
- return context.result;
- }
- }
-
- @Override
- public V putIfAbsent(K key, V value) {
- if (key == null || value == null) {
- throw new NullPointerException();
- }
- try (OperationContext<K, V> context = new OperationContext<>(this, key)) {
- super.compute(
- key,
- (k, v) -> {
- context.result = v;
- if (v != null) {
- return v;
- }
- return addChange(context, x -> value);
- });
- return context.result;
- }
- }
-
- @Override
- public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
- if (key == null || mappingFunction == null) {
- throw new NullPointerException();
- }
- try (OperationContext<K, V> context = new OperationContext<>(this, key)) {
- return super.computeIfAbsent(key, k -> addChange(context, mappingFunction));
- }
- }
-
- @Override
- public V computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
- if (key == null || remappingFunction == null) {
- throw new NullPointerException();
- }
- try (OperationContext<K, V> context = new OperationContext<>(this, key)) {
- return super.computeIfPresent(key, (k, v) -> addChange(context, x -> remappingFunction.apply(x, v)));
- }
- }
-
- @Override
- public V compute(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
- if (key == null || remappingFunction == null) {
- throw new NullPointerException();
- }
- try (OperationContext<K, V> context = new OperationContext<>(this, key)) {
- return super.compute(key, (k, v) -> addChange(context, x -> remappingFunction.apply(x, v)));
- }
- }
-
- @Override
- public V merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
- if (key == null || value == null || remappingFunction == null) {
- throw new NullPointerException();
- }
- try (OperationContext<K, V> context = new OperationContext<>(this, key)) {
- return super.compute(
- key,
- (k, oldValue) -> {
- V newValue = (oldValue == null) ? value : remappingFunction.apply(oldValue, value);
- return addChange(context, x -> newValue);
- });
- }
- }
-
- @Override
- public boolean replace(K key, V oldValue, V newValue) {
- if (key == null || oldValue == null || newValue == null) {
- throw new NullPointerException();
- }
- try (OperationContext<K, V> context = new OperationContext<>(this, key)) {
- super.computeIfPresent(
- key,
- (k, v) -> {
- if (Objects.equals(oldValue, v)) {
- context.result = addChange(context, x -> newValue);
- return context.result;
- }
- return v;
- });
- return context.result != null && Objects.equals(context.result, newValue);
- }
- }
-
- @Override
- public V replace(K key, V value) {
- if (key == null || value == null) {
- throw new NullPointerException();
- }
- try (OperationContext<K, V> context = new OperationContext<>(this, key)) {
- super.computeIfPresent(
- key,
- (k, v) -> {
- context.result = v;
- return addChange(context, x -> value);
- });
- return context.result;
- }
- }
-
- @Override
- public void putAll(Map<? extends K, ? extends V> m) {
- for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) {
- put(e.getKey(), e.getValue());
- }
- }
-
- @Override
- public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
- for (Map.Entry<? extends K, ? extends V> e : entrySet()) {
- replace(e.getKey(), e.getValue(), function.apply(e.getKey(), e.getValue()));
- }
- }
-
- @Override
- public Set<Entry<K, V>> entrySet() {
- return Collections.unmodifiableSet(super.entrySet());
- }
-
- /**
- * @return the size of the queue of changes.
- */
- int getQueueSize() {
- return totalChanges.intValue();
- }
-
- /**
- * Indicates whether an eviction is needed. An eviction can be triggered if the size of the map or the queue of
- * changes exceeds the maximum allowed size which is respectively {@code maximumCacheSize} and
- * {@code 2 * maximumCacheSize}.
- *
- * @return {@code true} if an eviction is needed, {@code false} otherwise.
- */
- private boolean evictionNeeded() {
- return size() > maximumCacheSize || getQueueSize() > 2 * maximumCacheSize;
- }
-
- /**
- * @return the oldest existing change.
- */
- private Entry<K, V> nextOldestChange() {
- Entry<K, V> oldest = lastChanges.poll();
- if (oldest != null) {
- totalChanges.decrement();
- }
- return oldest;
- }
-
- /**
- * The internal context of all write operations.
- */
- private static class OperationContext<K, V> implements AutoCloseable {
- /**
- * The result of the corresponding operation when applicable.
- */
- V result;
- /**
- * The key against which the operation is made.
- */
- final K key;
- /**
- * The underlying cache.
- */
- private final SimpleLRUCache<K, V> cache;
-
- OperationContext(SimpleLRUCache<K, V> cache, K key) {
- this.cache = cache;
- this.key = key;
- }
-
- @Override
- public void close() {
- if (cache.evictionNeeded() && cache.eviction.compareAndSet(false, true)) {
- try {
- while (cache.evictionNeeded()) {
- Entry<K, V> oldest = cache.nextOldestChange();
- if (oldest != null && cache.remove(oldest.getKey(), oldest.getValue())) {
- cache.evict.accept(oldest.getValue());
- }
- }
- } finally {
- cache.eviction.set(false);
- }
- }
- }
- }
+ return new SimpleSoftCache<>(
+ new SimpleLRUCache<K, SoftReference<V>>(
+ initialCapacity, maximumCacheSize,
+ asSoftReferenceConsumer(stopOnEviction
+ ? DefaultLRUCacheFactory.this::doStop : DefaultLRUCacheFactory.this::doNothing)));
}
<V> void doNothing(V value) {
diff --git a/core/camel-support/src/main/java/org/apache/camel/support/cache/SimpleLRUCache.java b/core/camel-support/src/main/java/org/apache/camel/support/cache/SimpleLRUCache.java
new file mode 100644
index 00000000000..c36c1640259
--- /dev/null
+++ b/core/camel-support/src/main/java/org/apache/camel/support/cache/SimpleLRUCache.java
@@ -0,0 +1,289 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * 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.apache.camel.support.cache;
+
+import java.util.Collections;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Queue;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.LongAdder;
+import java.util.function.BiFunction;
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+/**
+ * {@code SimpleLRUCache} is a simple implementation of a cache of type Least Recently Used . The implementation doesn't
+ * accept null values. Generally speaking, the parameters of all the public methods must have a value otherwise a
+ * {@code NullPointerException} is thrown.
+ *
+ * @param <K> type of the key
+ * @param <V> type of the value
+ */
+public class SimpleLRUCache<K, V> extends ConcurrentHashMap<K, V> {
+
+ static final float DEFAULT_LOAD_FACTOR = 0.75f;
+ /**
+ * The flag indicating that an eviction process is in progress.
+ */
+ private final AtomicBoolean eviction = new AtomicBoolean();
+ /**
+ * The maximum cache size.
+ */
+ private final int maximumCacheSize;
+ /**
+ * The last changes recorded.
+ */
+ private final Queue<Entry<K, V>> lastChanges = new ConcurrentLinkedQueue<>();
+ /**
+ * The total amount of changes recorded.
+ */
+ private final LongAdder totalChanges = new LongAdder();
+ /**
+ * The function to call when an entry is evicted.
+ */
+ private final Consumer<V> evict;
+
+ public SimpleLRUCache(int initialCapacity, int maximumCacheSize, Consumer<V> evicted) {
+ super(initialCapacity, DEFAULT_LOAD_FACTOR);
+ this.maximumCacheSize = maximumCacheSize;
+ this.evict = Objects.requireNonNull(evicted);
+ }
+
+ /**
+ * Adds a new change in case the mapping function doesn't return {@code null}.
+ *
+ * @param context the context of the write operation
+ * @param mappingFunction the mapping function to apply.
+ * @return the result of the mapping function.
+ */
+ private V addChange(OperationContext<K, V> context, Function<? super K, ? extends V> mappingFunction) {
+ K key = context.key;
+ V value = mappingFunction.apply(key);
+ if (value == null) {
+ return null;
+ }
+ lastChanges.add(Map.entry(key, value));
+ totalChanges.increment();
+ return value;
+ }
+
+ @Override
+ public V put(K key, V value) {
+ if (key == null || value == null) {
+ throw new NullPointerException();
+ }
+ try (OperationContext<K, V> context = new OperationContext<>(this, key)) {
+ super.compute(
+ key,
+ (k, v) -> {
+ context.result = v;
+ return addChange(context, x -> value);
+ });
+ return context.result;
+ }
+ }
+
+ @Override
+ public V putIfAbsent(K key, V value) {
+ if (key == null || value == null) {
+ throw new NullPointerException();
+ }
+ try (OperationContext<K, V> context = new OperationContext<>(this, key)) {
+ super.compute(
+ key,
+ (k, v) -> {
+ context.result = v;
+ if (v != null) {
+ return v;
+ }
+ return addChange(context, x -> value);
+ });
+ return context.result;
+ }
+ }
+
+ @Override
+ public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
+ if (key == null || mappingFunction == null) {
+ throw new NullPointerException();
+ }
+ try (OperationContext<K, V> context = new OperationContext<>(this, key)) {
+ return super.computeIfAbsent(key, k -> addChange(context, mappingFunction));
+ }
+ }
+
+ @Override
+ public V computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
+ if (key == null || remappingFunction == null) {
+ throw new NullPointerException();
+ }
+ try (OperationContext<K, V> context = new OperationContext<>(this, key)) {
+ return super.computeIfPresent(key, (k, v) -> addChange(context, x -> remappingFunction.apply(x, v)));
+ }
+ }
+
+ @Override
+ public V compute(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
+ if (key == null || remappingFunction == null) {
+ throw new NullPointerException();
+ }
+ try (OperationContext<K, V> context = new OperationContext<>(this, key)) {
+ return super.compute(key, (k, v) -> addChange(context, x -> remappingFunction.apply(x, v)));
+ }
+ }
+
+ @Override
+ public V merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
+ if (key == null || value == null || remappingFunction == null) {
+ throw new NullPointerException();
+ }
+ try (OperationContext<K, V> context = new OperationContext<>(this, key)) {
+ return super.compute(
+ key,
+ (k, oldValue) -> {
+ V newValue = (oldValue == null) ? value : remappingFunction.apply(oldValue, value);
+ return addChange(context, x -> newValue);
+ });
+ }
+ }
+
+ @Override
+ public boolean replace(K key, V oldValue, V newValue) {
+ if (key == null || oldValue == null || newValue == null) {
+ throw new NullPointerException();
+ }
+ try (OperationContext<K, V> context = new OperationContext<>(this, key)) {
+ super.computeIfPresent(
+ key,
+ (k, v) -> {
+ if (Objects.equals(oldValue, v)) {
+ context.result = addChange(context, x -> newValue);
+ return context.result;
+ }
+ return v;
+ });
+ return context.result != null && Objects.equals(context.result, newValue);
+ }
+ }
+
+ @Override
+ public V replace(K key, V value) {
+ if (key == null || value == null) {
+ throw new NullPointerException();
+ }
+ try (OperationContext<K, V> context = new OperationContext<>(this, key)) {
+ super.computeIfPresent(
+ key,
+ (k, v) -> {
+ context.result = v;
+ return addChange(context, x -> value);
+ });
+ return context.result;
+ }
+ }
+
+ @Override
+ public void putAll(Map<? extends K, ? extends V> m) {
+ for (Entry<? extends K, ? extends V> e : m.entrySet()) {
+ put(e.getKey(), e.getValue());
+ }
+ }
+
+ @Override
+ public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
+ for (Entry<? extends K, ? extends V> e : entrySet()) {
+ replace(e.getKey(), e.getValue(), function.apply(e.getKey(), e.getValue()));
+ }
+ }
+
+ @Override
+ public Set<Entry<K, V>> entrySet() {
+ return Collections.unmodifiableSet(super.entrySet());
+ }
+
+ /**
+ * @return the size of the queue of changes.
+ */
+ int getQueueSize() {
+ return totalChanges.intValue();
+ }
+
+ /**
+ * Indicates whether an eviction is needed. An eviction can be triggered if the size of the map or the queue of
+ * changes exceeds the maximum allowed size which is respectively {@code maximumCacheSize} and
+ * {@code 2 * maximumCacheSize}.
+ *
+ * @return {@code true} if an eviction is needed, {@code false} otherwise.
+ */
+ private boolean evictionNeeded() {
+ return size() > maximumCacheSize || getQueueSize() > 2 * maximumCacheSize;
+ }
+
+ /**
+ * @return the oldest existing change.
+ */
+ private Entry<K, V> nextOldestChange() {
+ Entry<K, V> oldest = lastChanges.poll();
+ if (oldest != null) {
+ totalChanges.decrement();
+ }
+ return oldest;
+ }
+
+ /**
+ * The internal context of all write operations.
+ */
+ private static class OperationContext<K, V> implements AutoCloseable {
+ /**
+ * The result of the corresponding operation when applicable.
+ */
+ V result;
+ /**
+ * The key against which the operation is made.
+ */
+ final K key;
+ /**
+ * The underlying cache.
+ */
+ private final SimpleLRUCache<K, V> cache;
+
+ OperationContext(SimpleLRUCache<K, V> cache, K key) {
+ this.cache = cache;
+ this.key = key;
+ }
+
+ @Override
+ public void close() {
+ if (cache.evictionNeeded() && cache.eviction.compareAndSet(false, true)) {
+ try {
+ while (cache.evictionNeeded()) {
+ Entry<K, V> oldest = cache.nextOldestChange();
+ if (oldest != null && cache.remove(oldest.getKey(), oldest.getValue())) {
+ cache.evict.accept(oldest.getValue());
+ }
+ }
+ } finally {
+ cache.eviction.set(false);
+ }
+ }
+ }
+ }
+}
diff --git a/core/camel-support/src/main/java/org/apache/camel/support/cache/SimpleSoftCache.java b/core/camel-support/src/main/java/org/apache/camel/support/cache/SimpleSoftCache.java
new file mode 100644
index 00000000000..72b52578fdc
--- /dev/null
+++ b/core/camel-support/src/main/java/org/apache/camel/support/cache/SimpleSoftCache.java
@@ -0,0 +1,388 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * 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.apache.camel.support.cache;
+
+import java.lang.ref.Reference;
+import java.lang.ref.SoftReference;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.function.BiConsumer;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+/**
+ * {@code SimpleSoftCache} is a simple implementation of a cache where values are soft references which allows the
+ * Garbage Collector to clear the referent in response of a memory demand to potentially prevent
+ * {@code OutOfMemoryError}. The entries where the referent is missing are removed lazily when they are accessed
+ * directly or indirectly through the {@code Map} API. The implementation doesn't accept null values. Generally
+ * speaking, the parameters of all the public methods must have a value otherwise a {@code NullPointerException} is
+ * thrown.
+ *
+ * @param <K> type of the key
+ * @param <V> type of the value
+ * @see SimpleLRUCache
+ */
+public class SimpleSoftCache<K, V> implements Map<K, V> {
+
+ /**
+ * The underlying cache to which the modifications are applied to.
+ */
+ private final Map<K, SoftReference<V>> delegate;
+
+ /**
+ * Constructs a {@code SimpleSoftCache} with the given underlying cache.
+ *
+ * @param delegate the underlying cache to which the modifications are applied to. Be aware that the implementation
+ * of the provided map must accept concurrent modifications to allow lazy evictions of empty
+ * references.
+ */
+ public SimpleSoftCache(Map<K, SoftReference<V>> delegate) {
+ this.delegate = delegate;
+ }
+
+ /**
+ * @return the size of the cache without considering if the soft references still have a referent set for the sake
+ * of simplicity and efficiency.
+ */
+ @Override
+ public int size() {
+ return delegate.size();
+ }
+
+ /**
+ * Returns true if this map contains no key-value mappings without considering if the soft references still have a
+ * referent set for the sake of simplicity and efficiency.
+ */
+ @Override
+ public boolean isEmpty() {
+ return delegate.isEmpty();
+ }
+
+ @Override
+ public boolean containsKey(Object key) {
+ return get(key) != null;
+ }
+
+ @Override
+ public boolean containsValue(Object value) {
+ for (Entry<K, SoftReference<V>> entry : delegate.entrySet()) {
+ SoftReference<V> ref = entry.getValue();
+ V refVal = ref.get();
+ if (refVal == null) {
+ delegate.remove(entry.getKey(), ref);
+ } else if (Objects.equals(value, refVal)) {
+ return true;
+ }
+ }
+ return false;
+ }
+
+ @Override
+ public V get(Object key) {
+ SoftReference<V> ref = delegate.get(key);
+ if (ref == null) {
+ return null;
+ }
+ V v = ref.get();
+ if (v == null) {
+ delegate.remove(key, ref);
+ }
+ return v;
+ }
+
+ @Override
+ public V put(K key, V value) {
+ SoftReference<V> prev = delegate.put(key, new SoftReference<>(value));
+ return prev == null ? null : prev.get();
+ }
+
+ @Override
+ public V remove(Object key) {
+ SoftReference<V> prev = delegate.remove(key);
+ return prev == null ? null : prev.get();
+ }
+
+ @Override
+ public void putAll(Map<? extends K, ? extends V> m) {
+ for (Entry<? extends K, ? extends V> e : m.entrySet()) {
+ delegate.put(e.getKey(), new SoftReference<>(e.getValue()));
+ }
+ }
+
+ @Override
+ public void clear() {
+ delegate.clear();
+ }
+
+ @Override
+ public Set<K> keySet() {
+ return delegate.keySet();
+ }
+
+ @Override
+ public Collection<V> values() {
+ return delegate.values().stream().map(Reference::get).filter(Objects::nonNull).collect(Collectors.toList());
+ }
+
+ @Override
+ public Set<Entry<K, V>> entrySet() {
+ Set<Entry<K, V>> result = new HashSet<>(delegate.size());
+ for (Entry<K, SoftReference<V>> entry : delegate.entrySet()) {
+ SoftReference<V> ref = entry.getValue();
+ V v = ref.get();
+ if (v == null) {
+ delegate.remove(entry.getKey(), ref);
+ continue;
+ }
+ result.add(Map.entry(entry.getKey(), v));
+ }
+ return result;
+ }
+
+ @Override
+ public void forEach(BiConsumer<? super K, ? super V> action) {
+ delegate.forEach((k, ref) -> {
+ V v = ref.get();
+ if (v == null) {
+ delegate.remove(k, ref);
+ } else {
+ action.accept(k, v);
+ }
+ });
+ }
+
+ @Override
+ public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
+ for (Entry<? extends K, ? extends V> e : entrySet()) {
+ replace(e.getKey(), e.getValue(), function.apply(e.getKey(), e.getValue()));
+ }
+ }
+
+ @Override
+ public V putIfAbsent(K key, V value) {
+ if (key == null || value == null) {
+ throw new NullPointerException();
+ }
+ for (;;) {
+ SoftReference<V> ref = delegate.get(key);
+ V prev = null;
+ if (ref == null) {
+ SoftReference<V> prevRef = delegate.putIfAbsent(key, new SoftReference<>(value));
+ if (prevRef != null && (prev = prevRef.get()) == null) {
+ // The referent is missing let's try again
+ delegate.remove(key, prevRef);
+ continue;
+ }
+ } else {
+ prev = ref.get();
+ if (prev == null && !delegate.replace(key, ref, new SoftReference<>(value))) {
+ // The state has changed, let's try again
+ continue;
+ }
+ }
+ return prev;
+ }
+ }
+
+ @Override
+ public boolean remove(Object key, Object value) {
+ if (key == null || value == null) {
+ throw new NullPointerException();
+ }
+ for (;;) {
+ SoftReference<V> ref = delegate.get(key);
+ if (ref != null) {
+ V v = ref.get();
+ if (v == null || Objects.equals(v, value)) {
+ if (delegate.remove(key, ref)) {
+ return v != null;
+ }
+ // The state has changed, let's try again
+ continue;
+ }
+ }
+ return false;
+ }
+ }
+
+ @Override
+ public boolean replace(K key, V oldValue, V newValue) {
+ if (key == null || oldValue == null || newValue == null) {
+ throw new NullPointerException();
+ }
+ for (;;) {
+ SoftReference<V> ref = delegate.get(key);
+ if (ref != null) {
+ V v = ref.get();
+ if (v == null) {
+ if (!delegate.remove(key, ref)) {
+ // The state has changed, let's try again
+ continue;
+ }
+ } else if (Objects.equals(v, oldValue)) {
+ if (!delegate.replace(key, ref, new SoftReference<>(newValue))) {
+ // The state has changed, let's try again
+ continue;
+ }
+ return true;
+ }
+ }
+ return false;
+ }
+ }
+
+ @Override
+ public V replace(K key, V value) {
+ if (key == null || value == null) {
+ throw new NullPointerException();
+ }
+ for (;;) {
+ SoftReference<V> ref = delegate.get(key);
+ if (ref != null) {
+ V v = ref.get();
+ if (v == null) {
+ if (!delegate.remove(key, ref)) {
+ // The state has changed, let's try again
+ continue;
+ }
+ } else if (!delegate.replace(key, ref, new SoftReference<>(value))) {
+ // The state has changed, let's try again
+ continue;
+ }
+ return v;
+ }
+ return null;
+ }
+ }
+
+ @Override
+ public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
+ if (key == null || mappingFunction == null) {
+ throw new NullPointerException();
+ }
+ for (;;) {
+ SoftReference<V> ref = delegate.get(key);
+ if (ref == null) {
+ V newValue = mappingFunction.apply(key);
+ if (newValue != null && delegate.putIfAbsent(key, new SoftReference<>(newValue)) != null) {
+ // The state has changed, let's try again
+ continue;
+ }
+ return newValue;
+ } else {
+ V v = ref.get();
+ if (v == null) {
+ // The referent is missing let's try again
+ delegate.remove(key, ref);
+ continue;
+ }
+ return v;
+ }
+ }
+ }
+
+ @Override
+ public V computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
+ if (key == null || remappingFunction == null) {
+ throw new NullPointerException();
+ }
+ for (;;) {
+ SoftReference<V> ref = delegate.get(key);
+ if (ref != null) {
+ V v = ref.get();
+ if (v == null) {
+ if (delegate.remove(key, ref)) {
+ return null;
+ }
+ // The state has changed, let's try again
+ continue;
+ }
+ V newValue = remappingFunction.apply(key, v);
+ if (newValue == null) {
+ if (!delegate.remove(key, ref)) {
+ // The state has changed, let's try again
+ continue;
+ }
+ } else if (!delegate.replace(key, ref, new SoftReference<>(newValue))) {
+ // The state has changed, let's try again
+ continue;
+ }
+ return newValue;
+ }
+ return null;
+ }
+ }
+
+ @Override
+ public V compute(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
+ if (key == null || remappingFunction == null) {
+ throw new NullPointerException();
+ }
+ for (;;) {
+ SoftReference<V> ref = delegate.get(key);
+ V oldValue = ref == null ? null : ref.get();
+ V newValue = remappingFunction.apply(key, oldValue);
+ if (newValue == null) {
+ // delete mapping
+ if (ref != null && !delegate.remove(key, ref)) {
+ // The state has changed, let's try again
+ continue;
+ }
+ } else if (ref == null) {
+ if (delegate.putIfAbsent(key, new SoftReference<>(newValue)) != null) {
+ // The state has changed, let's try again
+ continue;
+ }
+ } else if (!delegate.replace(key, ref, new SoftReference<>(newValue))) {
+ // The state has changed, let's try again
+ continue;
+ }
+ return newValue;
+ }
+ }
+
+ @Override
+ public V merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
+ if (key == null || value == null || remappingFunction == null) {
+ throw new NullPointerException();
+ }
+ for (;;) {
+ SoftReference<V> ref = delegate.get(key);
+ V oldValue = ref == null ? null : ref.get();
+ V newValue = oldValue == null ? value : remappingFunction.apply(oldValue, value);
+ if (newValue == null) {
+ if (!delegate.remove(key, ref)) {
+ // The state has changed, let's try again
+ continue;
+ }
+ } else if (ref == null) {
+ if (delegate.putIfAbsent(key, new SoftReference<>(newValue)) != null) {
+ // The state has changed, let's try again
+ continue;
+ }
+ } else if (!delegate.replace(key, ref, new SoftReference<>(newValue))) {
+ // The state has changed, let's try again
+ continue;
+ }
+ return newValue;
+ }
+ }
+}