Improve lambda-based EntityCallback detection.

In case an EntityCallback is declared as lambda expression, the JVM does not expose any generics information about the target entity type the callback shall be applied to. This commit changes the callback lookup and processing so that in case the generics information is not detectable on the type, we fall back to the BeanDefinition's resolvable type (fed by the factory method's return type which carries the necessary reflection information). That generics information is then kept in the newly introduce EntityCallbackAdapter and the code inspecting the actual entity type for matches then uses the resolvable type held in that. Also, the actual callback invocation is done on the adapter's delegate.

Removed the ability of the discoverer to register EntityCallbacks by bean name as that was not used in the public API at all and it avoids duplicating the bean definition type detection. A couple of minor additional cleanups (records for cache key, methods static where possible and with lower visibility etc.)

Fixes #2812.

Author: odrotbohm

src/main/java/org/springframework/data/mapping/callback/DefaultEntityCallbacks.java

@@ -21,7 +21,6 @@
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.core.ResolvableType;
 import org.springframework.util.Assert;
@@ -35,6 +34,7 @@
  *
  * @author Mark Paluch
  * @author Christoph Strobl
+ * @author Oliver Drotbohm
  * @since 2.2
  */
 class DefaultEntityCallbacks implements EntityCallbacks {
@@ -93,7 +93,8 @@ public void addEntityCallback(EntityCallback<?> callback) {
 		this.callbackDiscoverer.addEntityCallback(callback);
 	}
 
-	static class SimpleEntityCallbackInvoker implements org.springframework.data.mapping.callback.EntityCallbackInvoker {
+	static class SimpleEntityCallbackInvoker
+			implements org.springframework.data.mapping.callback.EntityCallbackInvoker {
 
 		@Override
 		public <T> T invokeCallback(EntityCallback<T> callback, T entity,
@@ -108,11 +109,12 @@ public <T> T invokeCallback(EntityCallback<T> callback, T entity,
 				}
 
 				throw new IllegalArgumentException(
-						String.format("Callback invocation on %s returned null value for %s", callback.getClass(), entity));
+						"Callback invocation on %s returned null value for %s".formatted(callback.getClass(), entity));
 
 			} catch (IllegalArgumentException | ClassCastException ex) {
 
 				String msg = ex.getMessage();
+
 				if (msg == null || EntityCallbackInvoker.matchesClassCastMessage(msg, entity.getClass())) {
 
 					// Possibly a lambda-defined listener which we could not resolve the generic event type for

src/main/java/org/springframework/data/mapping/callback/DefaultReactiveEntityCallbacks.java

@@ -24,7 +24,6 @@
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.reactivestreams.Publisher;
-
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.core.ResolvableType;
 import org.springframework.util.Assert;
@@ -38,6 +37,7 @@
  * @author Mark Paluch
  * @author Christoph Strobl
  * @author Michael J. Simons
+ * @author Oliver Drotbohm
  */
 class DefaultReactiveEntityCallbacks implements ReactiveEntityCallbacks {
 
@@ -63,11 +63,13 @@ class DefaultReactiveEntityCallbacks implements ReactiveEntityCallbacks {
 	}
 
 	@Override
+	@SuppressWarnings("unchecked")
 	public <T> Mono<T> callback(Class<? extends EntityCallback> callbackType, T entity, Object... args) {
 
 		Assert.notNull(entity, "Entity must not be null");
 
-		Class<T> entityType = (Class<T>) (entity != null ? ClassUtils.getUserClass(entity.getClass())
+		Class<T> entityType = (Class<T>) (entity != null
+				? ClassUtils.getUserClass(entity.getClass())
 				: callbackDiscoverer.resolveDeclaredEntityType(callbackType).getRawClass());
 
 		Method callbackMethod = callbackMethodCache.computeIfAbsent(callbackType, it -> {
@@ -112,7 +114,7 @@ public <T> Mono<T> invokeCallback(EntityCallback<T> callback, T entity,
 				}
 
 				throw new IllegalArgumentException(
-						String.format("Callback invocation on %s returned null value for %s", callback.getClass(), entity));
+						"Callback invocation on %s returned null value for %s".formatted(callback.getClass(), entity));
 			} catch (IllegalArgumentException | ClassCastException ex) {
 
 				String msg = ex.getMessage();