Add Coroutines support for @Cacheable

This commit adds Coroutines support for `@Cacheable`.

It also refines SimpleKeyGenerator to ignore Continuation
parameters (Kotlin does not allow to have the same method
signature with both suspending and non-suspending variants)
and refines
org.springframework.aop.framework.CoroutinesUtils.awaitSingleOrNull
in order to wrap plain value to Mono.

Closes gh-31412

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

@@ -48,6 +48,7 @@ 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.KotlinDetector;
 import org.springframework.core.ReactiveAdapter;
 import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.expression.EvaluationContext;
@@ -85,6 +86,7 @@ import org.springframework.util.function.SupplierUtils;
  * @author Phillip Webb
  * @author Sam Brannen
  * @author Stephane Nicoll
+ * @author Sebastien Deleuze
  * @since 3.1
  */
 public abstract class CacheAspectSupport extends AbstractCacheInvoker
@@ -1024,6 +1026,9 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 									() -> Mono.from(adapter.toPublisher(invokeOperation(invoker))).toFuture())));
 				}
 			}
+			if (KotlinDetector.isKotlinReflectPresent() && KotlinDetector.isSuspendingFunction(method)) {
+				return Mono.fromFuture(cache.retrieve(key, () -> ((Mono<?>) invokeOperation(invoker)).toFuture()));
+			}
 			return NOT_HANDLED;
 		}
 

spring-context/src/main/java/org/springframework/cache/interceptor/CacheInterceptor.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.
@@ -19,9 +19,15 @@ package org.springframework.cache.interceptor;
 import java.io.Serializable;
 import java.lang.reflect.Method;
 
+import kotlin.coroutines.Continuation;
+import kotlin.coroutines.CoroutineContext;
+import kotlinx.coroutines.Job;
 import org.aopalliance.intercept.MethodInterceptor;
 import org.aopalliance.intercept.MethodInvocation;
+import org.reactivestreams.Publisher;
 
+import org.springframework.core.CoroutinesUtils;
+import org.springframework.core.KotlinDetector;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
@@ -39,6 +45,7 @@ import org.springframework.util.Assert;
  *
  * @author Costin Leau
  * @author Juergen Hoeller
+ * @author Sebastien Deleuze
  * @since 3.1
  */
 @SuppressWarnings("serial")
@@ -51,6 +58,9 @@ public class CacheInterceptor extends CacheAspectSupport implements MethodInterc
 
 		CacheOperationInvoker aopAllianceInvoker = () -> {
 			try {
+				if (KotlinDetector.isKotlinReflectPresent() && KotlinDetector.isSuspendingFunction(method)) {
+					return KotlinDelegate.invokeSuspendingFunction(method, invocation.getThis(), invocation.getArguments());
+				}
 				return invocation.proceed();
 			}
 			catch (Throwable ex) {
@@ -68,4 +78,16 @@ public class CacheInterceptor extends CacheAspectSupport implements MethodInterc
 		}
 	}
 
+	/**
+	 * Inner class to avoid a hard dependency on Kotlin at runtime.
+	 */
+	private static class KotlinDelegate {
+
+		public static Publisher<?> invokeSuspendingFunction(Method method, Object target, Object... args) {
+			Continuation<?>  continuation = (Continuation<?>) args[args.length - 1];
+			CoroutineContext coroutineContext = continuation.getContext().minusKey(Job.Key);
+			return CoroutinesUtils.invokeSuspendingFunction(coroutineContext, method, target, args);
+		}
+	}
+
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 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 +17,9 @@
 package org.springframework.cache.interceptor;
 
 import java.lang.reflect.Method;
+import java.util.Arrays;
+
+import org.springframework.core.KotlinDetector;
 
 /**
  * Simple key generator. Returns the parameter itself if a single non-null
@@ -30,6 +33,7 @@ import java.lang.reflect.Method;
  *
  * @author Phillip Webb
  * @author Juergen Hoeller
+ * @author Sebastien Deleuze
  * @since 4.0
  * @see SimpleKey
  * @see org.springframework.cache.annotation.CachingConfigurer
@@ -38,7 +42,8 @@ public class SimpleKeyGenerator implements KeyGenerator {
 
 	@Override
 	public Object generate(Object target, Method method, Object... params) {
-		return generateKey(params);
+		return generateKey((KotlinDetector.isSuspendingFunction(method) ?
+				Arrays.copyOf(params, params.length - 1) : params));
 	}
 
 	/**

spring-context/src/main/java/org/springframework/context/expression/MethodBasedEvaluationContext.java

@@ -19,6 +19,7 @@ package org.springframework.context.expression;
 import java.lang.reflect.Method;
 import java.util.Arrays;
 
+import org.springframework.core.KotlinDetector;
 import org.springframework.core.ParameterNameDiscoverer;
 import org.springframework.expression.spel.support.StandardEvaluationContext;
 import org.springframework.lang.Nullable;
@@ -37,6 +38,7 @@ import org.springframework.util.ObjectUtils;
  *
  * @author Stephane Nicoll
  * @author Juergen Hoeller
+ * @author Sebastien Deleuze
  * @since 4.2
  */
 public class MethodBasedEvaluationContext extends StandardEvaluationContext {
@@ -55,7 +57,8 @@ public class MethodBasedEvaluationContext extends StandardEvaluationContext {
 
 		super(rootObject);
 		this.method = method;
-		this.arguments = arguments;
+		this.arguments = (KotlinDetector.isSuspendingFunction(method) ?
+				Arrays.copyOf(arguments, arguments.length - 1) : arguments);
 		this.parameterNameDiscoverer = parameterNameDiscoverer;
 	}