Add property to enable Caffeine async cache mode

CaffeineCacheManager supports asynchronous caches backed by Caffeine's
AsyncCache via setAsyncCacheMode, which adds support for Cache.retrieve.

Add a spring.cache.caffeine.async property (default false) wired to
CaffeineCacheManager.setAsyncCacheMode in CaffeineCacheConfiguration.

See gh-51844

Signed-off-by: seonghun lee <harrisleesh@gmail.com>

documentation/spring-boot-docs/src/docs/antora/modules/reference/pages/io/caching.adoc

@@ -223,6 +223,8 @@ If a javadoc:com.github.benmanes.caffeine.cache.CacheLoader[] bean is defined, i
 Since the javadoc:com.github.benmanes.caffeine.cache.CacheLoader[] is going to be associated with _all_ caches managed by the cache manager, it must be defined as `CacheLoader<Object, Object>`.
 The auto-configuration ignores any other generic type.
 
+To expose asynchronous caches backed by Caffeine's javadoc:com.github.benmanes.caffeine.cache.AsyncCache[], adding support for `Cache.retrieve`, set configprop:spring.cache.caffeine.async[] to `true`.
+
 
 
 [[io.caching.provider.cache2k]]

module/spring-boot-cache/src/main/java/org/springframework/boot/cache/autoconfigure/CacheProperties.java

@@ -122,6 +122,12 @@ public class CacheProperties {
 		 */
 		private @Nullable String spec;
 
+		/**
+		 * Whether to expose asynchronous caches backed by Caffeine's AsyncCache, adding
+		 * support for Cache.retrieve.
+		 */
+		private boolean async;
+
 		public @Nullable String getSpec() {
 			return this.spec;
 		}
@@ -130,6 +136,14 @@ public class CacheProperties {
 			this.spec = spec;
 		}
 
+		public boolean isAsync() {
+			return this.async;
+		}
+
+		public void setAsync(boolean async) {
+			this.async = async;
+		}
+
 	}
 
 	/**

module/spring-boot-cache/src/main/java/org/springframework/boot/cache/autoconfigure/CaffeineCacheConfiguration.java

@@ -61,6 +61,7 @@ class CaffeineCacheConfiguration {
 			ObjectProvider<Caffeine<Object, Object>> caffeine, ObjectProvider<CaffeineSpec> caffeineSpec,
 			ObjectProvider<CacheLoader<Object, Object>> cacheLoader) {
 		CaffeineCacheManager cacheManager = new CaffeineCacheManager();
+		cacheManager.setAsyncCacheMode(cacheProperties.getCaffeine().isAsync());
 		setCacheBuilder(cacheProperties, caffeineSpec.getIfAvailable(), caffeine.getIfAvailable(), cacheManager);
 		cacheLoader.ifAvailable(cacheManager::setCacheLoader);
 		return cacheManager;

module/spring-boot-cache/src/test/java/org/springframework/boot/cache/autoconfigure/CacheAutoConfigurationTests.java

@@ -80,6 +80,7 @@ import org.springframework.data.redis.connection.RedisConnectionFactory;
 import org.springframework.test.util.ReflectionTestUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.BDDMockito.given;
 import static org.mockito.BDDMockito.then;
@@ -813,6 +814,31 @@ class CacheAutoConfigurationTests extends AbstractCacheAutoConfigurationTests {
 			.run(this::validateCaffeineCacheWithStats);
 	}
 
+	@Test
+	void caffeineCacheWithAsyncCacheMode() {
+		this.contextRunner.withUserConfiguration(DefaultCacheConfiguration.class)
+			.withPropertyValues("spring.cache.type=caffeine", "spring.cache.caffeine.async=true",
+					"spring.cache.cacheNames=foo")
+			.run((context) -> {
+				CaffeineCacheManager manager = getCacheManager(context, CaffeineCacheManager.class);
+				CaffeineCache foo = (CaffeineCache) manager.getCache("foo");
+				assertThat(foo).isNotNull();
+				assertThat(foo.getAsyncCache()).isNotNull();
+			});
+	}
+
+	@Test
+	void caffeineCacheWithoutAsyncCacheModeByDefault() {
+		this.contextRunner.withUserConfiguration(DefaultCacheConfiguration.class)
+			.withPropertyValues("spring.cache.type=caffeine", "spring.cache.cacheNames=foo")
+			.run((context) -> {
+				CaffeineCacheManager manager = getCacheManager(context, CaffeineCacheManager.class);
+				CaffeineCache foo = (CaffeineCache) manager.getCache("foo");
+				assertThat(foo).isNotNull();
+				assertThatIllegalStateException().isThrownBy(foo::getAsyncCache);
+			});
+	}
+
 	@Test
 	void autoConfiguredCacheManagerCanBeSwapped() {
 		this.contextRunner.withUserConfiguration(CacheManagerPostProcessorConfiguration.class)