DATACMNS-934 - BasicPersistentEntity.addAssociation(…) drops null values now.

Previously a null value was added to the list of associations if it was handed to BasicaPersistentEntity.addAssociation(…). We now drop those null values and log a warning as it usually indicates a MappingContext implementation identifying a property as association but subsequently failing to look it up.

Author: odrotbohm

src/main/java/org/springframework/data/mapping/model/BasicPersistentEntity.java

@@ -30,6 +30,8 @@
 import java.util.Set;
 import java.util.TreeSet;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.data.annotation.TypeAlias;
 import org.springframework.data.mapping.Association;
@@ -58,7 +60,9 @@
  */
 public class BasicPersistentEntity<T, P extends PersistentProperty<P>> implements MutablePersistentEntity<T, P> {
 
+	private static final Logger LOGGER = LoggerFactory.getLogger(BasicPersistentEntity.class);
 	private static final String TYPE_MISMATCH = "Target bean of type %s is not of type of the persistent entity (%s)!";
+	private static final String NULL_ASSOCIATION = "%s.addAssociation(…) was called with a null association! Usually indicates a problem in a Spring Data MappingContext implementation. Be sure to file a bug at https://jira.spring.io!";
 
 	private final PreferredConstructor<T, P> constructor;
 	private final TypeInformation<T> information;
@@ -236,11 +240,17 @@ protected P returnPropertyIfBetterIdPropertyCandidateOrNull(P property) {
 		return property;
 	}
 
-	/* (non-Javadoc)
+	/*
+	 * (non-Javadoc)
 	 * @see org.springframework.data.mapping.MutablePersistentEntity#addAssociation(org.springframework.data.mapping.model.Association)
 	 */
 	public void addAssociation(Association<P> association) {
 
+		if (association == null) {
+			LOGGER.warn(String.format(NULL_ASSOCIATION, this.getClass().getName()));
+			return;
+		}
+
 		if (!associations.contains(association)) {
 			associations.add(association);
 		}

src/test/java/org/springframework/data/mapping/model/BasicPersistentEntityUnitTests.java

@@ -27,6 +27,7 @@
 import java.util.List;
 
 import org.hamcrest.CoreMatchers;
+import org.junit.Assert;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
@@ -39,11 +40,13 @@
 import org.springframework.data.annotation.CreatedDate;
 import org.springframework.data.annotation.LastModifiedBy;
 import org.springframework.data.annotation.TypeAlias;
+import org.springframework.data.mapping.Association;
 import org.springframework.data.mapping.PersistentEntity;
 import org.springframework.data.mapping.PersistentEntitySpec;
 import org.springframework.data.mapping.PersistentProperty;
 import org.springframework.data.mapping.PersistentPropertyAccessor;
 import org.springframework.data.mapping.Person;
+import org.springframework.data.mapping.SimpleAssociationHandler;
 import org.springframework.data.mapping.context.SampleMappingContext;
 import org.springframework.data.mapping.context.SamplePersistentProperty;
 import org.springframework.data.util.ClassTypeInformation;
@@ -275,6 +278,24 @@ public void invalidBeanAccessCreatesDescriptiveErrorMessage() {
 		entity.getPropertyAccessor(new Object());
 	}
 
+	/**
+	 * @see DATACMNS-934
+	 */
+	@Test
+	public void doesNotThrowAnExceptionForNullAssociation() {
+
+		BasicPersistentEntity<Entity, T> entity = createEntity(Entity.class);
+		entity.addAssociation(null);
+
+		entity.doWithAssociations(new SimpleAssociationHandler() {
+
+			@Override
+			public void doWithAssociation(Association<? extends PersistentProperty<?>> association) {
+				Assert.fail("Expected the method to never be called!");
+			}
+		});
+	}
+
 	private <S> BasicPersistentEntity<S, T> createEntity(Class<S> type) {
 		return createEntity(type, null);
 	}