Cache operation invocation hook point

This commit adds a invokeOperation protected method in case one
needs a hook point in the way the underlying cache method is invoked,
and how exceptions that might be thrown by that invocation are handled.

Issue: SPR-11540

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

@@ -284,6 +284,20 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 		return invoker.invoke();
 	}
 
+	/**
+	 * Execute the underlying operation (typically in case of cache miss) and return
+	 * the result of the invocation. If an exception occurs it will be wrapped in
+	 * a {@link CacheOperationInvoker.ThrowableWrapper}: the exception can be handled
+	 * or modified but it <em>must</em> be wrapped in a
+	 * {@link CacheOperationInvoker.ThrowableWrapper} as well.
+	 * @param invoker the invoker handling the operation being cached
+	 * @return the result of the invocation
+	 * @see CacheOperationInvoker#invoke()
+	 */
+	protected Object invokeOperation(CacheOperationInvoker invoker) {
+		return invoker.invoke();
+	}
+
 	private Class<?> getTargetClass(Object target) {
 		Class<?> targetClass = AopProxyUtils.ultimateTargetClass(target);
 		if (targetClass == null && target != null) {
@@ -314,7 +328,7 @@ public abstract class CacheAspectSupport extends AbstractCacheInvoker
 
 		// Invoke the method if don't have a cache hit
 		if (result == null) {
-			result = new SimpleValueWrapper(invoker.invoke());
+			result = new SimpleValueWrapper(invokeOperation(invoker));
 		}
 
 		// Collect any explicit @CachePuts

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

@@ -19,9 +19,10 @@ package org.springframework.cache.interceptor;
 /**
  * Abstract the invocation of a cache operation.
  *
- * <p>Provide a special exception that can be used to indicate that the
- * underlying invocation has thrown a checked exception, allowing the
- * callers to threat these in a different manner if necessary.
+ * <p>Does not provide a way to transmit checked exceptions but
+ * provide a special exception that should be used to wrap any
+ * exception that was thrown by the underlying invocation. Callers
+ * are expected to handle this issue type specifically.
  *
  * @author Stephane Nicoll
  * @since 4.1
@@ -29,11 +30,11 @@ package org.springframework.cache.interceptor;
 public interface CacheOperationInvoker {
 
 	/**
-	 * Invoke the cache operation defined by this instance. Can throw a
-	 * {@link ThrowableWrapper} if that operation wants to explicitly
-	 * indicate that a checked exception has occurred.
+	 * Invoke the cache operation defined by this instance. Wraps any
+	 * exception that is thrown during the invocation in a
+	 * {@link ThrowableWrapper}.
 	 * @return the result of the operation
-	 * @throws ThrowableWrapper if a checked exception has been thrown
+	 * @throws ThrowableWrapper if an error occurred while invoking the operation
 	 */
 	Object invoke() throws ThrowableWrapper;