DATAMONGO-505 - Fixed handling of parameter binding of associations and collection values.

Instead of converting given association values as-is, ConvertingParameterAccessor now converts each collection value into a DBRef individually.

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/ConvertingParameterAccessor.java

@@ -15,7 +15,11 @@
  */
 package org.springframework.data.mongodb.repository.query;
 
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
 import java.util.Iterator;
+import java.util.List;
 
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort;
@@ -25,6 +29,9 @@ import org.springframework.data.mongodb.core.geo.Point;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
 import org.springframework.data.repository.query.ParameterAccessor;
 import org.springframework.util.Assert;
+import org.springframework.util.CollectionUtils;
+
+import com.mongodb.DBRef;
 
 /**
  * Custom {@link ParameterAccessor} that uses a {@link MongoWriter} to serialize parameters into Mongo format.
@@ -158,7 +165,28 @@ public class ConvertingParameterAccessor implements MongoParameterAccessor {
 		 * @see org.springframework.data.mongodb.repository.ConvertingParameterAccessor.PotentiallConvertingIterator#nextConverted()
 		 */
 		public Object nextConverted(MongoPersistentProperty property) {
-			return property.isAssociation() ? writer.toDBRef(next(), property) : getConvertedValue(next());
+
+			Object next = next();
+
+			if (next == null) {
+				return null;
+			}
+
+			if (property.isAssociation()) {
+				if (next.getClass().isArray() || next instanceof Iterable) {
+
+					List<DBRef> dbRefs = new ArrayList<DBRef>();
+					for (Object element : asCollection(next)) {
+						dbRefs.add(writer.toDBRef(element, property));
+					}
+
+					return dbRefs;
+				} else {
+					return writer.toDBRef(next, property);
+				}
+			}
+
+			return getConvertedValue(next);
 		}
 
 		/*
@@ -170,6 +198,33 @@ public class ConvertingParameterAccessor implements MongoParameterAccessor {
 		}
 	}
 
+	/**
+	 * Returns the given object as {@link Collection}. Will do a copy of it if it implements {@link Iterable} or is an
+	 * array. Will return an empty {@link Collection} in case {@literal null} is given. Will wrap all other types into a
+	 * single-element collction
+	 * 
+	 * @param source
+	 * @return
+	 */
+	private static Collection<?> asCollection(Object source) {
+
+		if (source instanceof Iterable) {
+
+			List<Object> result = new ArrayList<Object>();
+			for (Object element : (Iterable<?>) source) {
+				result.add(element);
+			}
+
+			return result;
+		}
+
+		if (source == null) {
+			return Collections.emptySet();
+		}
+
+		return source.getClass().isArray() ? CollectionUtils.arrayToList(source) : Collections.singleton(source);
+	}
+
 	/**
 	 * Custom {@link Iterator} that adds a method to access elements in a converted manner.
 	 * 

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/repository/query/ConvertingParameterAccessorUnitTests.java

@@ -15,11 +15,13 @@
  */
 package org.springframework.data.mongodb.repository.query;
 
-import static org.mockito.Mockito.*;
+import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
-import static org.hamcrest.CoreMatchers.*;
+import static org.mockito.Mockito.*;
 
 import java.util.Arrays;
+import java.util.Collection;
+
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -27,7 +29,11 @@ import org.mockito.Mock;
 import org.mockito.runners.MockitoJUnitRunner;
 import org.springframework.data.mongodb.MongoDbFactory;
 import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
+import org.springframework.data.mongodb.core.mapping.DBRef;
 import org.springframework.data.mongodb.core.mapping.MongoMappingContext;
+import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
+import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
+import org.springframework.data.mongodb.repository.query.ConvertingParameterAccessor.PotentiallyConvertingIterator;
 
 import com.mongodb.BasicDBList;
 
@@ -76,4 +82,66 @@ public class ConvertingParameterAccessorUnitTests {
 
 		assertThat(result, is((Object) reference));
 	}
+
+	/**
+	 * @see DATAMONGO-505
+	 */
+	@Test
+	public void convertsAssociationsToDBRef() {
+
+		Property property = new Property();
+		property.id = 5L;
+
+		Object result = setupAndConvert(property);
+
+		assertThat(result, is(instanceOf(com.mongodb.DBRef.class)));
+		com.mongodb.DBRef dbRef = (com.mongodb.DBRef) result;
+		assertThat(dbRef.getRef(), is("property"));
+		assertThat(dbRef.getId(), is((Object) 5L));
+	}
+
+	/**
+	 * @see DATAMONGO-505
+	 */
+	@Test
+	public void convertsAssociationsToDBRefForCollections() {
+
+		Property property = new Property();
+		property.id = 5L;
+
+		Object result = setupAndConvert(Arrays.asList(property));
+
+		assertThat(result, is(instanceOf(Collection.class)));
+		Collection<?> collection = (Collection<?>) result;
+
+		assertThat(collection, hasSize(1));
+		Object element = collection.iterator().next();
+
+		assertThat(element, is(instanceOf(com.mongodb.DBRef.class)));
+		com.mongodb.DBRef dbRef = (com.mongodb.DBRef) element;
+		assertThat(dbRef.getRef(), is("property"));
+		assertThat(dbRef.getId(), is((Object) 5L));
+	}
+
+	private Object setupAndConvert(Object... parameters) {
+
+		MongoParameterAccessor delegate = new StubParameterAccessor(parameters);
+		PotentiallyConvertingIterator iterator = new ConvertingParameterAccessor(converter, delegate).iterator();
+
+		MongoPersistentEntity<?> entity = context.getPersistentEntity(Entity.class);
+		MongoPersistentProperty property = entity.getPersistentProperty("property");
+
+		return iterator.nextConverted(property);
+	}
+
+	static class Entity {
+
+		@DBRef
+		Property property;
+	}
+
+	static class Property {
+
+		Long id;
+	}
 }