DATACMNS-1596 - Modules not exposing identifying annotations do not claim repository interfaces anymore.

Previously, a module not exposing any entity identifying annotations would have claimed a repository definition and potentially overrode the bean definition of another store that was the proper claim in the first place. We have now changed this to abstain from a claim of the interface.

We' also tweaked the log output in the following cases:

1. If the module neither returns an identifying type nor entity identifying annotations, we now log a warning that a module does not support a multi-module setup and answer all assignment requests with false.

2. The info level warning indicating an interface has been dropped now reports which annotations or interface base types to use.

Original pull request: #411.
Related tickets: spring-projects/spring-boot#18721

src/main/java/org/springframework/data/repository/config/RepositoryConfigurationExtensionSupport.java

@@ -23,6 +23,7 @@ import java.util.Collections;
 import java.util.HashSet;
 import java.util.Set;
 import java.util.function.Supplier;
+import java.util.stream.Collectors;
 
 import javax.annotation.Nullable;
 
@@ -53,7 +54,9 @@ public abstract class RepositoryConfigurationExtensionSupport implements Reposit
 
 	private static final Logger LOGGER = LoggerFactory.getLogger(RepositoryConfigurationExtensionSupport.class);
 	private static final String CLASS_LOADING_ERROR = "%s - Could not load type %s using class loader %s.";
-	private static final String MULTI_STORE_DROPPED = "Spring Data {} - Could not safely identify store assignment for repository candidate {}.";
+	private static final String MULTI_STORE_DROPPED = "Spring Data %s - Could not safely identify store assignment for repository candidate %s. If you want this repository to be a %s repository,";
+
+	private boolean noMultiStoreSupport = false;
 
 	/*
 	 * (non-Javadoc)
@@ -294,7 +297,22 @@ public abstract class RepositoryConfigurationExtensionSupport implements Reposit
 	 */
 	protected boolean isStrictRepositoryCandidate(RepositoryMetadata metadata) {
 
+		if (noMultiStoreSupport) {
+			return false;
+		}
+
 		Collection<Class<?>> types = getIdentifyingTypes();
+		Collection<Class<? extends Annotation>> annotations = getIdentifyingAnnotations();
+		String moduleName = getModuleName();
+
+		if (types.isEmpty() && annotations.isEmpty()) {
+			if (!noMultiStoreSupport) {
+				LOGGER.warn("Spring Data {} does not support multi-store setups!", moduleName);
+				noMultiStoreSupport = true;
+				return false;
+			}
+		}
+
 		Class<?> repositoryInterface = metadata.getRepositoryInterface();
 
 		for (Class<?> type : types) {
@@ -304,11 +322,6 @@ public abstract class RepositoryConfigurationExtensionSupport implements Reposit
 		}
 
 		Class<?> domainType = metadata.getDomainType();
-		Collection<Class<? extends Annotation>> annotations = getIdentifyingAnnotations();
-
-		if (annotations.isEmpty()) {
-			return true;
-		}
 
 		for (Class<? extends Annotation> annotationType : annotations) {
 			if (AnnotationUtils.findAnnotation(domainType, annotationType) != null) {
@@ -316,7 +329,23 @@ public abstract class RepositoryConfigurationExtensionSupport implements Reposit
 			}
 		}
 
-		LOGGER.info(MULTI_STORE_DROPPED, getModuleName(), repositoryInterface);
+		String message = String.format(MULTI_STORE_DROPPED, moduleName, repositoryInterface, moduleName);
+
+		if (!annotations.isEmpty()) {
+			message = message.concat(" consider annotating your entities with one of these annotations: ") //
+					.concat(toString(annotations)) //
+					.concat(types.isEmpty() ? "." : " (preferred)");
+		}
+
+		if (!types.isEmpty()) {
+
+			message = message.concat(annotations.isEmpty() ? " consider" : ", or consider") //
+					.concat(" extending one of the following types with your repository: ") //
+					.concat(toString(types)) //
+					.concat(".");
+		}
+
+		LOGGER.info(message);
 
 		return false;
 	}
@@ -364,4 +393,11 @@ public abstract class RepositoryConfigurationExtensionSupport implements Reposit
 
 		return null;
 	}
+
+	private static String toString(Collection<? extends Class<?>> types) {
+
+		return types.stream() //
+				.map(Class::getName) //
+				.collect(Collectors.joining(", "));
+	}
 }