Add caching annotation support for CompletableFuture and reactive return values

Includes CompletableFuture-based retrieve operations on Spring's Cache interface.
Includes support for retrieve operations on CaffeineCache and ConcurrentMapCache.
Includes async cache mode option on CaffeineCacheManager.

Closes gh-17559
Closes gh-17920
Closes gh-30122

spring-context/src/main/java/org/springframework/cache/Cache.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -17,20 +17,28 @@
 package org.springframework.cache;
 
 import java.util.concurrent.Callable;
+import java.util.concurrent.CompletableFuture;
+import java.util.function.Supplier;
 
 import org.springframework.lang.Nullable;
 
 /**
  * Interface that defines common cache operations.
  *
- * <b>Note:</b> Due to the generic use of caching, it is recommended that
- * implementations allow storage of {@code null} values (for example to
- * cache methods that return {@code null}).
+ * <p>Serves as an SPI for Spring's annotation-based caching model
+ * ({@link org.springframework.cache.annotation.Cacheable} and co)
+ * as well as an API for direct usage in applications.
+ *
+ * <p><b>Note:</b> Due to the generic use of caching, it is recommended
+ * that implementations allow storage of {@code null} values
+ * (for example to cache methods that return {@code null}).
  *
  * @author Costin Leau
  * @author Juergen Hoeller
  * @author Stephane Nicoll
  * @since 3.1
+ * @see CacheManager
+ * @see org.springframework.cache.annotation.Cacheable
  */
 public interface Cache {
 
@@ -100,6 +108,51 @@ public interface Cache {
 	@Nullable
 	<T> T get(Object key, Callable<T> valueLoader);
 
+	/**
+	 * Return the value to which this cache maps the specified key,
+	 * wrapped in a {@link CompletableFuture}. This operation must not block
+	 * but is allowed to return a completed {@link CompletableFuture} if the
+	 * corresponding value is immediately available.
+	 * <p>Returns {@code null} if the cache contains no mapping for this key;
+	 * otherwise, the cached value (which may be {@code null} itself) will
+	 * be returned in the {@link CompletableFuture}.
+	 * @param key the key whose associated value is to be returned
+	 * @return the value to which this cache maps the specified key,
+	 * contained within a {@link CompletableFuture} which may also hold
+	 * a cached {@code null} value. A straight {@code null} being
+	 * returned means that the cache contains no mapping for this key.
+	 * @since 6.1
+	 * @see #get(Object)
+	 */
+	@Nullable
+	default CompletableFuture<?> retrieve(Object key) {
+		throw new UnsupportedOperationException(
+				getClass().getName() + " does not support CompletableFuture-based retrieval");
+	}
+
+	/**
+	 * Return the value to which this cache maps the specified key, obtaining
+	 * that value from {@code valueLoader} if necessary. This method provides
+	 * a simple substitute for the conventional "if cached, return; otherwise
+	 * create, cache and return" pattern, based on {@link CompletableFuture}.
+	 * This operation must not block.
+	 * <p>If possible, implementations should ensure that the loading operation
+	 * is synchronized so that the specified {@code valueLoader} is only called
+	 * once in case of concurrent access on the same key.
+	 * <p>If the {@code valueLoader} throws an exception, it will be propagated
+	 * to the {@code CompletableFuture} handle returned from here.
+	 * @param key the key whose associated value is to be returned
+	 * @return the value to which this cache maps the specified key,
+	 * contained within a {@link CompletableFuture}
+	 * @since 6.1
+	 * @see #retrieve(Object)
+	 * @see #get(Object, Callable)
+	 */
+	default <T> CompletableFuture<T> retrieve(Object key, Supplier<CompletableFuture<T>> valueLoader) {
+		throw new UnsupportedOperationException(
+				getClass().getName() + " does not support CompletableFuture-based retrieval");
+	}
+
 	/**
 	 * Associate the specified value with the specified key in this cache.
 	 * <p>If the cache previously contained a mapping for this key, the old
@@ -108,6 +161,11 @@ public interface Cache {
 	 * fashion, with subsequent lookups possibly not seeing the entry yet.
 	 * This may for example be the case with transactional cache decorators.
 	 * Use {@link #putIfAbsent} for guaranteed immediate registration.
+	 * <p>If the cache is supposed to be compatible with {@link CompletableFuture}
+	 * and reactive interactions, the put operation needs to be effectively
+	 * non-blocking, with any backend write-through happening asynchronously.
+	 * This goes along with a cache implemented and configured to support
+	 * {@link #retrieve(Object)} and {@link #retrieve(Object, Supplier)}.
 	 * @param key the key with which the specified value is to be associated
 	 * @param value the value to be associated with the specified key
 	 * @see #putIfAbsent(Object, Object)
@@ -156,6 +214,11 @@ public interface Cache {
 	 * fashion, with subsequent lookups possibly still seeing the entry.
 	 * This may for example be the case with transactional cache decorators.
 	 * Use {@link #evictIfPresent} for guaranteed immediate removal.
+	 * <p>If the cache is supposed to be compatible with {@link CompletableFuture}
+	 * and reactive interactions, the evict operation needs to be effectively
+	 * non-blocking, with any backend write-through happening asynchronously.
+	 * This goes along with a cache implemented and configured to support
+	 * {@link #retrieve(Object)} and {@link #retrieve(Object, Supplier)}.
 	 * @param key the key whose mapping is to be removed from the cache
 	 * @see #evictIfPresent(Object)
 	 */
@@ -188,6 +251,11 @@ public interface Cache {
 	 * fashion, with subsequent lookups possibly still seeing the entries.
 	 * This may for example be the case with transactional cache decorators.
 	 * Use {@link #invalidate()} for guaranteed immediate removal of entries.
+	 * <p>If the cache is supposed to be compatible with {@link CompletableFuture}
+	 * and reactive interactions, the clear operation needs to be effectively
+	 * non-blocking, with any backend write-through happening asynchronously.
+	 * This goes along with a cache implemented and configured to support
+	 * {@link #retrieve(Object)} and {@link #retrieve(Object, Supplier)}.
 	 * @see #invalidate()
 	 */
 	void clear();

spring-context/src/main/java/org/springframework/cache/concurrent/ConcurrentMapCache.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -17,8 +17,11 @@
 package org.springframework.cache.concurrent;
 
 import java.util.concurrent.Callable;
+import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.ForkJoinPool;
+import java.util.function.Supplier;
 
 import org.springframework.cache.support.AbstractValueAdaptingCache;
 import org.springframework.core.serializer.support.SerializationDelegate;
@@ -26,13 +29,17 @@ import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
- * Simple {@link org.springframework.cache.Cache} implementation based on the
- * core JDK {@code java.util.concurrent} package.
+ * Simple {@link org.springframework.cache.Cache} implementation based on the core
+ * JDK {@code java.util.concurrent} package.
  *
  * <p>Useful for testing or simple caching scenarios, typically in combination
  * with {@link org.springframework.cache.support.SimpleCacheManager} or
  * dynamically through {@link ConcurrentMapCacheManager}.
  *
+ * <p>Supports the  {@link #retrieve(Object)} and {@link #retrieve(Object, Supplier)}
+ * operations in a best-effort fashion, relying on default {@link CompletableFuture}
+ * execution (typically within the JVM's {@link ForkJoinPool#commonPool()}).
+ *
  * <p><b>Note:</b> As {@link ConcurrentHashMap} (the default implementation used)
  * does not allow for {@code null} values to be stored, this class will replace
  * them with a predefined internal object. This behavior can be changed through the
@@ -149,6 +156,20 @@ public class ConcurrentMapCache extends AbstractValueAdaptingCache {
 		}));
 	}
 
+	@Override
+	@Nullable
+	public CompletableFuture<?> retrieve(Object key) {
+		Object value = lookup(key);
+		return (value != null ? CompletableFuture.completedFuture(fromStoreValue(value)) : null);
+	}
+
+	@SuppressWarnings("unchecked")
+	@Override
+	public <T> CompletableFuture<T> retrieve(Object key, Supplier<CompletableFuture<T>> valueLoader) {
+		return CompletableFuture.supplyAsync(() ->
+				(T) fromStoreValue(this.store.computeIfAbsent(key, k -> toStoreValue(valueLoader.get().join()))));
+	}
+
 	@Override
 	public void put(Object key, @Nullable Object value) {
 		this.store.put(key, toStoreValue(value));

spring-context/src/main/java/org/springframework/cache/interceptor/CacheAspectSupport.java

@@ -24,11 +24,16 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Supplier;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.reactivestreams.Subscriber;
+import org.reactivestreams.Subscription;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
 
 import org.springframework.aop.framework.AopProxyUtils;
 import org.springframework.aop.support.AopUtils;
@@ -43,6 +48,8 @@ import org.springframework.cache.Cache;
 import org.springframework.cache.CacheManager;
 import org.springframework.context.expression.AnnotatedElementKey;
 import org.springframework.core.BridgeMethodResolver;
+import org.springframework.core.ReactiveAdapter;
+import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.expression.EvaluationContext;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
@@ -83,12 +90,18 @@ import org.springframework.util.function.SupplierUtils;
 public abstract class CacheAspectSupport extends AbstractCacheInvoker
 		implements BeanFactoryAware, InitializingBean, SmartInitializingSingleton {
 
+	private static final boolean reactiveStreamsPresent = ClassUtils.isPresent(
+			"org.reactivestreams.Publisher", CacheAspectSupport.class.getClassLoader());
+
 	protected final Log logger = LogFactory.getLog(getClass());
 
 	private final Map<CacheOperationCacheKey, CacheOperationMetadata> metadataCache = new ConcurrentHashMap<>(1024);
 
 	private final CacheOperationExpressionEvaluator evaluator = new CacheOperationExpressionEvaluator();
 
+	@Nullable
+	private final ReactiveCachingHandler reactiveCachingHandler;
+
 	@Nullable
 	private CacheOperationSource cacheOperationSource;
 
@@ -103,6 +116,11 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 	private boolean initialized = false;
 
 
+	protected CacheAspectSupport() {
+		this.reactiveCachingHandler = (reactiveStreamsPresent ? new ReactiveCachingHandler() : null);
+	}
+
+
 	/**
 	 * Configure this aspect with the given error handler, key generator and cache resolver/manager
 	 * suppliers, applying the corresponding default if a supplier is not resolvable.
@@ -371,41 +389,25 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 	}
 
 	@Nullable
-	private Object execute(final CacheOperationInvoker invoker, Method method, CacheOperationContexts contexts) {
-		// Special handling of synchronized invocation
+	private Object execute(CacheOperationInvoker invoker, Method method, CacheOperationContexts contexts) {
 		if (contexts.isSynchronized()) {
-			CacheOperationContext context = contexts.get(CacheableOperation.class).iterator().next();
-			if (isConditionPassing(context, CacheOperationExpressionEvaluator.NO_RESULT)) {
-				Object key = generateKey(context, CacheOperationExpressionEvaluator.NO_RESULT);
-				Cache cache = context.getCaches().iterator().next();
-				try {
-					return wrapCacheValue(method, handleSynchronizedGet(invoker, key, cache));
-				}
-				catch (Cache.ValueRetrievalException ex) {
-					// Directly propagate ThrowableWrapper from the invoker,
-					// or potentially also an IllegalArgumentException etc.
-					ReflectionUtils.rethrowRuntimeException(ex.getCause());
-				}
-			}
-			else {
-				// No caching required, just call the underlying method
-				return invokeOperation(invoker);
-			}
+			// Special handling of synchronized invocation
+			return executeSynchronized(invoker, method, contexts);
 		}
 
 		// Process any early evictions
 		processCacheEvicts(contexts.get(CacheEvictOperation.class), true,
 				CacheOperationExpressionEvaluator.NO_RESULT);
 
-		// Check if we have a cached item matching the conditions
-		Cache.ValueWrapper cacheHit = findCachedItem(contexts.get(CacheableOperation.class));
+		// Check if we have a cached value matching the conditions
+		Object cacheHit = findCachedValue(contexts.get(CacheableOperation.class));
 
 		Object cacheValue;
 		Object returnValue;
 
 		if (cacheHit != null && !hasCachePut(contexts)) {
 			// If there are no put requests, just use the cache hit
-			cacheValue = cacheHit.get();
+			cacheValue = (cacheHit instanceof Cache.ValueWrapper wrapper ? wrapper.get() : cacheHit);
 			returnValue = wrapCacheValue(method, cacheValue);
 		}
 		else {
@@ -414,8 +416,8 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 			cacheValue = unwrapReturnValue(returnValue);
 		}
 
-		// Collect puts from any @Cacheable miss, if no cached item is found
-		List<CachePutRequest> cachePutRequests = new ArrayList<>();
+		// Collect puts from any @Cacheable miss, if no cached value is found
+		List<CachePutRequest> cachePutRequests = new ArrayList<>(1);
 		if (cacheHit == null) {
 			collectPutRequests(contexts.get(CacheableOperation.class), cacheValue, cachePutRequests);
 		}
@@ -425,29 +427,52 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 
 		// Process any collected put requests, either from @CachePut or a @Cacheable miss
 		for (CachePutRequest cachePutRequest : cachePutRequests) {
-			cachePutRequest.apply(cacheValue);
+			Object returnOverride = cachePutRequest.apply(cacheValue);
+			if (returnOverride != null) {
+				returnValue = returnOverride;
+			}
 		}
 
 		// Process any late evictions
-		processCacheEvicts(contexts.get(CacheEvictOperation.class), false, cacheValue);
+		Object returnOverride = processCacheEvicts(
+				contexts.get(CacheEvictOperation.class), false, returnValue);
+		if (returnOverride != null) {
+			returnValue = returnOverride;
+		}
 
 		return returnValue;
 	}
 
 	@Nullable
-	private Object handleSynchronizedGet(CacheOperationInvoker invoker, Object key, Cache cache) {
-		InvocationAwareResult invocationResult = new InvocationAwareResult();
-		Object result = cache.get(key, () -> {
-			invocationResult.invoked = true;
-			if (logger.isTraceEnabled()) {
-				logger.trace("No cache entry for key '" + key + "' in cache " + cache.getName());
+	private Object executeSynchronized(CacheOperationInvoker invoker, Method method, CacheOperationContexts contexts) {
+		CacheOperationContext context = contexts.get(CacheableOperation.class).iterator().next();
+		if (isConditionPassing(context, CacheOperationExpressionEvaluator.NO_RESULT)) {
+			Object key = generateKey(context, CacheOperationExpressionEvaluator.NO_RESULT);
+			Cache cache = context.getCaches().iterator().next();
+			if (CompletableFuture.class.isAssignableFrom(method.getReturnType())) {
+				return cache.retrieve(key, () -> (CompletableFuture<?>) invokeOperation(invoker));
+			}
+			if (this.reactiveCachingHandler != null) {
+				Object returnValue = this.reactiveCachingHandler.executeSynchronized(invoker, method, cache, key);
+				if (returnValue != ReactiveCachingHandler.NOT_HANDLED) {
+					return returnValue;
+				}
+			}
+			try {
+				return wrapCacheValue(method, cache.get(key, () -> unwrapReturnValue(invokeOperation(invoker))));
+			}
+			catch (Cache.ValueRetrievalException ex) {
+				// Directly propagate ThrowableWrapper from the invoker,
+				// or potentially also an IllegalArgumentException etc.
+				ReflectionUtils.rethrowRuntimeException(ex.getCause());
+				// Never reached
+				return null;
 			}
-			return unwrapReturnValue(invokeOperation(invoker));
-		});
-		if (!invocationResult.invoked && logger.isTraceEnabled()) {
-			logger.trace("Cache entry for key '" + key + "' found in cache '" + cache.getName() + "'");
 		}
-		return result;
+		else {
+			// No caching required, just call the underlying method
+			return invokeOperation(invoker);
+		}
 	}
 
 	@Nullable
@@ -467,7 +492,7 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 	private boolean hasCachePut(CacheOperationContexts contexts) {
 		// Evaluate the conditions *without* the result object because we don't have it yet...
 		Collection<CacheOperationContext> cachePutContexts = contexts.get(CachePutOperation.class);
-		Collection<CacheOperationContext> excluded = new ArrayList<>();
+		Collection<CacheOperationContext> excluded = new ArrayList<>(1);
 		for (CacheOperationContext context : cachePutContexts) {
 			try {
 				if (!context.isConditionPassing(CacheOperationExpressionEvaluator.RESULT_UNAVAILABLE)) {
@@ -482,32 +507,55 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 		return (cachePutContexts.size() != excluded.size());
 	}
 
-	private void processCacheEvicts(
-			Collection<CacheOperationContext> contexts, boolean beforeInvocation, @Nullable Object result) {
+	@Nullable
+	private Object processCacheEvicts(Collection<CacheOperationContext> contexts, boolean beforeInvocation,
+			@Nullable Object result) {
 
-		for (CacheOperationContext context : contexts) {
-			CacheEvictOperation operation = (CacheEvictOperation) context.metadata.operation;
-			if (beforeInvocation == operation.isBeforeInvocation() && isConditionPassing(context, result)) {
-				performCacheEvict(context, operation, result);
+		if (contexts.isEmpty()) {
+			return null;
+		}
+		List<CacheOperationContext> applicable = contexts.stream()
+				.filter(context -> (context.metadata.operation instanceof CacheEvictOperation evict &&
+						beforeInvocation == evict.isBeforeInvocation())).toList();
+		if (applicable.isEmpty()) {
+			return null;
+		}
+
+		if (result instanceof CompletableFuture<?> future) {
+			return future.whenComplete((value, ex) -> {
+				if (ex == null) {
+					performCacheEvicts(applicable, result);
+				}
+			});
+		}
+		if (this.reactiveCachingHandler != null) {
+			Object returnValue = this.reactiveCachingHandler.processCacheEvicts(applicable, result);
+			if (returnValue != ReactiveCachingHandler.NOT_HANDLED) {
+				return returnValue;
 			}
 		}
+		performCacheEvicts(applicable, result);
+		return null;
 	}
 
-	private void performCacheEvict(
-			CacheOperationContext context, CacheEvictOperation operation, @Nullable Object result) {
-
-		Object key = null;
-		for (Cache cache : context.getCaches()) {
-			if (operation.isCacheWide()) {
-				logInvalidating(context, operation, null);
-				doClear(cache, operation.isBeforeInvocation());
-			}
-			else {
-				if (key == null) {
-					key = generateKey(context, result);
+	private void performCacheEvicts(List<CacheOperationContext> contexts, @Nullable Object result) {
+		for (CacheOperationContext context : contexts) {
+			CacheEvictOperation operation = (CacheEvictOperation) context.metadata.operation;
+			if (isConditionPassing(context, result)) {
+				Object key = null;
+				for (Cache cache : context.getCaches()) {
+					if (operation.isCacheWide()) {
+						logInvalidating(context, operation, null);
+						doClear(cache, operation.isBeforeInvocation());
+					}
+					else {
+						if (key == null) {
+							key = generateKey(context, result);
+						}
+						logInvalidating(context, operation, key);
+						doEvict(cache, key, operation.isBeforeInvocation());
+					}
 				}
-				logInvalidating(context, operation, key);
-				doEvict(cache, key, operation.isBeforeInvocation());
 			}
 		}
 	}
@@ -520,19 +568,21 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 	}
 
 	/**
-	 * Find a cached item only for {@link CacheableOperation} that passes the condition.
+	 * Find a cached value only for {@link CacheableOperation} that passes the condition.
 	 * @param contexts the cacheable operations
-	 * @return a {@link Cache.ValueWrapper} holding the cached item,
+	 * @return a {@link Cache.ValueWrapper} holding the cached value,
 	 * or {@code null} if none is found
 	 */
 	@Nullable
-	private Cache.ValueWrapper findCachedItem(Collection<CacheOperationContext> contexts) {
-		Object result = CacheOperationExpressionEvaluator.NO_RESULT;
+	private Object findCachedValue(Collection<CacheOperationContext> contexts) {
 		for (CacheOperationContext context : contexts) {
-			if (isConditionPassing(context, result)) {
-				Object key = generateKey(context, result);
-				Cache.ValueWrapper cached = findInCaches(context, key);
+			if (isConditionPassing(context, CacheOperationExpressionEvaluator.NO_RESULT)) {
+				Object key = generateKey(context, CacheOperationExpressionEvaluator.NO_RESULT);
+				Object cached = findInCaches(context, key);
 				if (cached != null) {
+					if (logger.isTraceEnabled()) {
+						logger.trace("Cache entry for key '" + key + "' found in cache(s) " + context.getCacheNames());
+					}
 					return cached;
 				}
 				else {
@@ -547,9 +597,9 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 
 	/**
 	 * Collect the {@link CachePutRequest} for all {@link CacheOperation} using
-	 * the specified result item.
+	 * the specified result value.
 	 * @param contexts the contexts to handle
-	 * @param result the result item (never {@code null})
+	 * @param result the result value (never {@code null})
 	 * @param putRequests the collection to update
 	 */
 	private void collectPutRequests(Collection<CacheOperationContext> contexts,
@@ -564,15 +614,18 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 	}
 
 	@Nullable
-	private Cache.ValueWrapper findInCaches(CacheOperationContext context, Object key) {
+	private Object findInCaches(CacheOperationContext context, Object key) {
 		for (Cache cache : context.getCaches()) {
-			Cache.ValueWrapper wrapper = doGet(cache, key);
-			if (wrapper != null) {
-				if (logger.isTraceEnabled()) {
-					logger.trace("Cache entry for key '" + key + "' found in cache '" + cache.getName() + "'");
-				}
-				return wrapper;
+			if (CompletableFuture.class.isAssignableFrom(context.getMethod().getReturnType())) {
+				return cache.retrieve(key);
 			}
+			if (this.reactiveCachingHandler != null) {
+				Object returnValue = this.reactiveCachingHandler.findInCaches(context, cache, key);
+				if (returnValue != ReactiveCachingHandler.NOT_HANDLED) {
+					return returnValue;
+				}
+			}
+			return doGet(cache, key);
 		}
 		return null;
 	}
@@ -625,13 +678,13 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 		}
 
 		private boolean determineSyncFlag(Method method) {
-			List<CacheOperationContext> cacheOperationContexts = this.contexts.get(CacheableOperation.class);
-			if (cacheOperationContexts == null) {  // no @Cacheable operation at all
+			List<CacheOperationContext> cacheableContexts = this.contexts.get(CacheableOperation.class);
+			if (cacheableContexts == null) {  // no @Cacheable operation at all
 				return false;
 			}
 			boolean syncEnabled = false;
-			for (CacheOperationContext cacheOperationContext : cacheOperationContexts) {
-				if (((CacheableOperation) cacheOperationContext.getOperation()).isSync()) {
+			for (CacheOperationContext context : cacheableContexts) {
+				if (context.getOperation() instanceof CacheableOperation cacheable && cacheable.isSync()) {
 					syncEnabled = true;
 					break;
 				}
@@ -641,13 +694,13 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 					throw new IllegalStateException(
 							"A sync=true operation cannot be combined with other cache operations on '" + method + "'");
 				}
-				if (cacheOperationContexts.size() > 1) {
+				if (cacheableContexts.size() > 1) {
 					throw new IllegalStateException(
 							"Only one sync=true operation is allowed on '" + method + "'");
 				}
-				CacheOperationContext cacheOperationContext = cacheOperationContexts.iterator().next();
-				CacheOperation operation = cacheOperationContext.getOperation();
-				if (cacheOperationContext.getCaches().size() > 1) {
+				CacheOperationContext cacheableContext = cacheableContexts.iterator().next();
+				CacheOperation operation = cacheableContext.getOperation();
+				if (cacheableContext.getCaches().size() > 1) {
 					throw new IllegalStateException(
 							"A sync=true operation is restricted to a single cache on '" + operation + "'");
 				}
@@ -720,7 +773,7 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 			this.args = extractArgs(metadata.method, args);
 			this.target = target;
 			this.caches = CacheAspectSupport.this.getCaches(this, metadata.cacheResolver);
-			this.cacheNames = createCacheNames(this.caches);
+			this.cacheNames = prepareCacheNames(this.caches);
 		}
 
 		@Override
@@ -808,8 +861,8 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 			return this.cacheNames;
 		}
 
-		private Collection<String> createCacheNames(Collection<? extends Cache> caches) {
-			Collection<String> names = new ArrayList<>();
+		private Collection<String> prepareCacheNames(Collection<? extends Cache> caches) {
+			Collection<String> names = new ArrayList<>(caches.size());
 			for (Cache cache : caches) {
 				names.add(cache.getName());
 			}
@@ -818,25 +871,6 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 	}
 
 
-	private class CachePutRequest {
-
-		private final CacheOperationContext context;
-
-		private final Object key;
-
-		public CachePutRequest(CacheOperationContext context, Object key) {
-			this.context = context;
-			this.key = key;
-		}
-
-		public void apply(@Nullable Object result) {
-			for (Cache cache : this.context.getCaches()) {
-				doPut(cache, this.key, result);
-			}
-		}
-	}
-
-
 	private static final class CacheOperationCacheKey implements Comparable<CacheOperationCacheKey> {
 
 		private final CacheOperation cacheOperation;
@@ -876,12 +910,168 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 	}
 
 
-	/**
-	 * Internal holder class for recording that a cache method was invoked.
-	 */
-	private static class InvocationAwareResult {
+	private class CachePutRequest {
 
-		boolean invoked;
+		private final CacheOperationContext context;
+
+		private final Object key;
+
+		public CachePutRequest(CacheOperationContext context, Object key) {
+			this.context = context;
+			this.key = key;
+		}
+
+		@Nullable
+		public Object apply(@Nullable Object result) {
+			if (result instanceof CompletableFuture<?> future) {
+				return future.whenComplete((value, ex) -> {
+					if (ex != null) {
+						performEvict(ex);
+					}
+					else {
+						performPut(value);
+					}
+				});
+			}
+			if (reactiveCachingHandler != null) {
+				Object returnValue = reactiveCachingHandler.processPutRequest(this, result);
+				if (returnValue != ReactiveCachingHandler.NOT_HANDLED) {
+					return returnValue;
+				}
+			}
+			performPut(result);
+			return null;
+		}
+
+		void performPut(@Nullable Object value) {
+			if (logger.isTraceEnabled()) {
+				logger.trace("Creating cache entry for key '" + this.key + "' in cache(s) " +
+						this.context.getCacheNames());
+			}
+			for (Cache cache : this.context.getCaches()) {
+				doPut(cache, this.key, value);
+			}
+		}
+
+		void performEvict(Throwable cause) {
+			if (logger.isTraceEnabled()) {
+				logger.trace("Removing cache entry for key '" + this.key + "' from cache(s) " +
+						this.context.getCacheNames() + " due to exception: " + cause);
+			}
+			for (Cache cache : this.context.getCaches()) {
+				doEvict(cache, this.key, false);
+			}
+		}
+	}
+
+
+	/**
+	 * Reactive Streams Subscriber collection for collecting a List to cache.
+	 */
+	private class CachePutListSubscriber implements Subscriber<Object> {
+
+		private final CachePutRequest request;
+
+		private final List<Object> cacheValue = new ArrayList<>();
+
+		public CachePutListSubscriber(CachePutRequest request) {
+			this.request = request;
+		}
+
+		@Override
+		public void onSubscribe(Subscription s) {
+			s.request(Integer.MAX_VALUE);
+		}
+		@Override
+		public void onNext(Object o) {
+			this.cacheValue.add(o);
+		}
+		@Override
+		public void onError(Throwable t) {
+			this.request.performEvict(t);
+		}
+		@Override
+		public void onComplete() {
+			this.request.performPut(this.cacheValue);
+		}
+	}
+
+
+	/**
+	 * Inner class to avoid a hard dependency on the Reactive Streams API at runtime.
+	 */
+	private class ReactiveCachingHandler {
+
+		public static final Object NOT_HANDLED = new Object();
+
+		private final ReactiveAdapterRegistry registry = ReactiveAdapterRegistry.getSharedInstance();
+
+		@Nullable
+		public Object executeSynchronized(CacheOperationInvoker invoker, Method method, Cache cache, Object key) {
+			ReactiveAdapter adapter = this.registry.getAdapter(method.getReturnType());
+			if (adapter != null) {
+				if (adapter.isMultiValue()) {
+					// Flux or similar
+					return adapter.fromPublisher(Flux.from(Mono.fromFuture(
+							cache.retrieve(key,
+									() -> Flux.from(adapter.toPublisher(invokeOperation(invoker))).collectList().toFuture())))
+							.flatMap(Flux::fromIterable));
+				}
+				else {
+					// Mono or similar
+					return adapter.fromPublisher(Mono.fromFuture(
+							cache.retrieve(key,
+									() -> Mono.from(adapter.toPublisher(invokeOperation(invoker))).toFuture())));
+				}
+			}
+			return NOT_HANDLED;
+		}
+
+		@Nullable
+		public Object processCacheEvicts(List<CacheOperationContext> contexts, @Nullable Object result) {
+			ReactiveAdapter adapter = (result != null ? this.registry.getAdapter(result.getClass()) : null);
+			if (adapter != null) {
+				return adapter.fromPublisher(Mono.from(adapter.toPublisher(result))
+						.doOnSuccess(value -> performCacheEvicts(contexts, result)));
+			}
+			return NOT_HANDLED;
+		}
+
+		@Nullable
+		public Object findInCaches(CacheOperationContext context, Cache cache, Object key) {
+			ReactiveAdapter adapter = this.registry.getAdapter(context.getMethod().getReturnType());
+			if (adapter != null) {
+				CompletableFuture<?> cachedFuture = cache.retrieve(key);
+				if (cachedFuture == null) {
+					return null;
+				}
+				if (adapter.isMultiValue()) {
+					return adapter.fromPublisher(Flux.from(Mono.fromFuture(cachedFuture))
+							.flatMap(v -> (v instanceof Iterable<?> iv ? Flux.fromIterable(iv) : Flux.just(v))));
+				}
+				else {
+					return adapter.fromPublisher(Mono.fromFuture(cachedFuture));
+				}
+			}
+			return NOT_HANDLED;
+		}
+
+		@Nullable
+		public Object processPutRequest(CachePutRequest request, @Nullable Object result) {
+			ReactiveAdapter adapter = (result != null ? this.registry.getAdapter(result.getClass()) : null);
+			if (adapter != null) {
+				if (adapter.isMultiValue()) {
+					Flux<?> source = Flux.from(adapter.toPublisher(result));
+					source.subscribe(new CachePutListSubscriber(request));
+					return adapter.fromPublisher(source);
+				}
+				else {
+					return adapter.fromPublisher(Mono.from(adapter.toPublisher(result))
+							.doOnSuccess(request::performPut).doOnError(request::performEvict));
+				}
+			}
+			return NOT_HANDLED;
+		}
 	}
 
 }

spring-context/src/main/java/org/springframework/cache/support/NoOpCache.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -17,6 +17,8 @@
 package org.springframework.cache.support;
 
 import java.util.concurrent.Callable;
+import java.util.concurrent.CompletableFuture;
+import java.util.function.Supplier;
 
 import org.springframework.cache.Cache;
 import org.springframework.lang.Nullable;
@@ -80,6 +82,17 @@ public class NoOpCache implements Cache {
 		}
 	}
 
+	@Override
+	@Nullable
+	public CompletableFuture<?> retrieve(Object key) {
+		return null;
+	}
+
+	@Override
+	public <T> CompletableFuture<T> retrieve(Object key, Supplier<CompletableFuture<T>> valueLoader) {
+		return valueLoader.get();
+	}
+
 	@Override
 	public void put(Object key, @Nullable Object value) {
 	}