Stop resolving CachingConfigurer instances eagerly

Closes gh-27751

spring-aspects/src/test/java/org/springframework/cache/aspectj/AspectJEnableCachingIsolatedTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -20,7 +20,6 @@ import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
 
-import org.springframework.beans.factory.BeanCreationException;
 import org.springframework.cache.CacheManager;
 import org.springframework.cache.annotation.CachingConfigurerSupport;
 import org.springframework.cache.annotation.EnableCaching;
@@ -107,10 +106,7 @@ public class AspectJEnableCachingIsolatedTests {
 		try {
 			load(MultiCacheManagerConfigurer.class, EnableCachingConfig.class);
 		}
-		catch (BeanCreationException ex) {
-			Throwable root = ex.getRootCause();
-			boolean condition = root instanceof IllegalStateException;
-			assertThat(condition).isTrue();
+		catch (IllegalStateException ex) {
 			assertThat(ex.getMessage().contains("implementations of CachingConfigurer")).isTrue();
 		}
 	}

spring-context-support/src/main/java/org/springframework/cache/jcache/config/AbstractJCacheConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -20,7 +20,6 @@ import java.util.function.Supplier;
 
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.cache.annotation.AbstractCachingConfiguration;
-import org.springframework.cache.annotation.CachingConfigurer;
 import org.springframework.cache.interceptor.CacheResolver;
 import org.springframework.cache.jcache.interceptor.DefaultJCacheOperationSource;
 import org.springframework.cache.jcache.interceptor.JCacheOperationSource;
@@ -46,11 +45,14 @@ public abstract class AbstractJCacheConfiguration extends AbstractCachingConfigu
 
 
 	@Override
-	protected void useCachingConfigurer(CachingConfigurer config) {
-		super.useCachingConfigurer(config);
-		if (config instanceof JCacheConfigurer) {
-			this.exceptionCacheResolver = ((JCacheConfigurer) config)::exceptionCacheResolver;
-		}
+	protected void useCachingConfigurer(CachingConfigurerSupplier cachingConfigurerSupplier) {
+		super.useCachingConfigurer(cachingConfigurerSupplier);
+		this.exceptionCacheResolver = cachingConfigurerSupplier.adapt(config -> {
+			if (config instanceof JCacheConfigurer) {
+				return ((JCacheConfigurer) config).exceptionCacheResolver();
+			}
+			return null;
+		});
 	}
 
 	@Bean(name = "jCacheOperationSource")

spring-context/src/main/java/org/springframework/cache/annotation/AbstractCachingConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -16,9 +16,12 @@
 
 package org.springframework.cache.annotation;
 
-import java.util.Collection;
+import java.util.List;
+import java.util.function.Function;
 import java.util.function.Supplier;
+import java.util.stream.Collectors;
 
+import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.cache.CacheManager;
 import org.springframework.cache.interceptor.CacheErrorHandler;
@@ -30,6 +33,7 @@ import org.springframework.core.annotation.AnnotationAttributes;
 import org.springframework.core.type.AnnotationMetadata;
 import org.springframework.lang.Nullable;
 import org.springframework.util.CollectionUtils;
+import org.springframework.util.function.SingletonSupplier;
 
 /**
  * Abstract base {@code @Configuration} class providing common structure
@@ -70,29 +74,60 @@ public abstract class AbstractCachingConfiguration implements ImportAware {
 		}
 	}
 
-	@Autowired(required = false)
-	void setConfigurers(Collection<CachingConfigurer> configurers) {
-		if (CollectionUtils.isEmpty(configurers)) {
-			return;
-		}
-		if (configurers.size() > 1) {
-			throw new IllegalStateException(configurers.size() + " implementations of " +
-					"CachingConfigurer were found when only 1 was expected. " +
-					"Refactor the configuration such that CachingConfigurer is " +
-					"implemented only once or not at all.");
-		}
-		CachingConfigurer configurer = configurers.iterator().next();
-		useCachingConfigurer(configurer);
+	@Autowired
+	void setConfigurers(ObjectProvider<CachingConfigurer> configurers) {
+		Supplier<CachingConfigurer> cachingConfigurer = () -> {
+			List<CachingConfigurer> candidates = configurers.stream().collect(Collectors.toList());
+			if (CollectionUtils.isEmpty(candidates)) {
+				return null;
+			}
+			if (candidates.size() > 1) {
+				throw new IllegalStateException(candidates.size() + " implementations of " +
+						"CachingConfigurer were found when only 1 was expected. " +
+						"Refactor the configuration such that CachingConfigurer is " +
+						"implemented only once or not at all.");
+			}
+			return candidates.get(0);
+		};
+		useCachingConfigurer(new CachingConfigurerSupplier(cachingConfigurer));
 	}
 
 	/**
 	 * Extract the configuration from the nominated {@link CachingConfigurer}.
 	 */
-	protected void useCachingConfigurer(CachingConfigurer config) {
-		this.cacheManager = config::cacheManager;
-		this.cacheResolver = config::cacheResolver;
-		this.keyGenerator = config::keyGenerator;
-		this.errorHandler = config::errorHandler;
+	protected void useCachingConfigurer(CachingConfigurerSupplier cachingConfigurerSupplier) {
+		this.cacheManager = cachingConfigurerSupplier.adapt(CachingConfigurer::cacheManager);
+		this.cacheResolver = cachingConfigurerSupplier.adapt(CachingConfigurer::cacheResolver);
+		this.keyGenerator = cachingConfigurerSupplier.adapt(CachingConfigurer::keyGenerator);
+		this.errorHandler = cachingConfigurerSupplier.adapt(CachingConfigurer::errorHandler);
+	}
+
+
+	protected static class CachingConfigurerSupplier {
+
+		private final Supplier<CachingConfigurer> supplier;
+
+		public CachingConfigurerSupplier(Supplier<CachingConfigurer> supplier) {
+			this.supplier = SingletonSupplier.of(supplier);
+		}
+
+		/**
+		 * Adapt the {@link CachingConfigurer} supplier to another supplier
+		 * provided by the specified mapping function. If the underlying
+		 * {@link CachingConfigurer} is {@code null}, {@code null} is returned
+		 * and the mapping function is not invoked.
+		 * @param provider the provider to use to adapt the supplier
+		 * @param <T> the type of the supplier
+		 * @return another supplier mapped by the specified function
+		 */
+		@Nullable
+		public <T> Supplier<T> adapt(Function<CachingConfigurer, T> provider) {
+			return () -> {
+				CachingConfigurer cachingConfigurer = this.supplier.get();
+				return (cachingConfigurer != null) ? provider.apply(cachingConfigurer) : null;
+			};
+		}
+
 	}
 
 }

spring-context/src/test/java/org/springframework/cache/config/EnableCachingTests.java

@@ -18,7 +18,6 @@ package org.springframework.cache.config;
 
 import org.junit.jupiter.api.Test;
 
-import org.springframework.beans.factory.BeanCreationException;
 import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.beans.factory.NoUniqueBeanDefinitionException;
 import org.springframework.cache.CacheManager;
@@ -107,11 +106,8 @@ public class EnableCachingTests extends AbstractCacheAnnotationTests {
 		try {
 			ctx.refresh();
 		}
-		catch (BeanCreationException ex) {
-			Throwable root = ex.getRootCause();
-			boolean condition = root instanceof IllegalStateException;
-			assertThat(condition).isTrue();
-			assertThat(root.getMessage().contains("implementations of CachingConfigurer")).isTrue();
+		catch (IllegalStateException ex) {
+			assertThat(ex.getMessage().contains("implementations of CachingConfigurer")).isTrue();
 		}
 	}