Prevent key extraction if a keyset value is null.

Follow the changes in data commons that renamed scroll to window.
Also error when a certain scroll position does not allow creating a query out of it because of null values.

See: #4308
Original Pull Request: #4317

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/EntityOperations.java

@@ -21,6 +21,7 @@ import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.Optional;
 
+import org.bson.BsonNull;
 import org.bson.Document;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.dao.InvalidDataAccessApiUsageException;
@@ -471,6 +472,7 @@ class EntityOperations {
 		 * @param sortObject
 		 * @return
 		 * @since 3.1
+		 * @throws IllegalStateException if a sort key yields {@literal null}.
 		 */
 		Map<String, Object> extractKeys(Document sortObject);
 
@@ -600,7 +602,14 @@ class EntityOperations {
 			keyset.put(ID_FIELD, getId());
 
 			for (String key : sortObject.keySet()) {
-				keyset.put(key, BsonUtils.resolveValue(map, key));
+				Object value = BsonUtils.resolveValue(map, key);
+
+				if (value == null) {
+					throw new IllegalStateException(
+							String.format("Cannot extract value for key %s because its value is null", key));
+				}
+
+				keyset.put(key, value);
 			}
 
 			return keyset;
@@ -756,14 +765,22 @@ class EntityOperations {
 
 			for (String key : sortObject.keySet()) {
 
+				Object value;
 				if (key.indexOf('.') != -1) {
 
 					// follow the path across nested levels.
 					// TODO: We should have a MongoDB-specific property path abstraction to allow diving into Document.
-					keyset.put(key, getNestedPropertyValue(key));
+					value = getNestedPropertyValue(key);
 				} else {
-					keyset.put(key, getPropertyValue(key));
+					value = getPropertyValue(key);
 				}
+
+				if (value == null) {
+					throw new IllegalStateException(
+							String.format("Cannot extract value for key %s because its value is null", key));
+				}
+
+				keyset.put(key, value);
 			}
 
 			return keyset;
@@ -774,7 +791,7 @@ class EntityOperations {
 
 			String[] segments = key.split("\\.");
 			Entity<?> currentEntity = this;
-			Object currentValue = null;
+			Object currentValue = BsonNull.VALUE;
 
 			for (int i = 0; i < segments.length; i++) {
 
@@ -786,7 +803,7 @@ class EntityOperations {
 				}
 			}
 
-			return currentValue;
+			return currentValue != null ? currentValue : BsonNull.VALUE;
 		}
 	}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ExecutableFindOperation.java

@@ -20,7 +20,7 @@ import java.util.Optional;
 import java.util.stream.Stream;
 
 import org.springframework.dao.DataAccessException;
-import org.springframework.data.domain.Scroll;
+import org.springframework.data.domain.Window;
 import org.springframework.data.domain.ScrollPosition;
 import org.springframework.data.geo.GeoResults;
 import org.springframework.data.mongodb.core.query.CriteriaDefinition;
@@ -126,16 +126,17 @@ public interface ExecutableFindOperation {
 		Stream<T> stream();
 
 		/**
-		 * Return a scroll of elements either starting or resuming at
+		 * Return a window of elements either starting or resuming at
 		 * {@link org.springframework.data.domain.ScrollPosition}.
 		 *
 		 * @param scrollPosition the scroll position.
-		 * @return a scroll of the resulting elements.
+		 * @return a window of the resulting elements.
+		 * @throws IllegalStateException if a potential {@literal KeysetScrollPosition} contains an invalid position.
 		 * @since 4.1
 		 * @see org.springframework.data.domain.OffsetScrollPosition
 		 * @see org.springframework.data.domain.KeysetScrollPosition
 		 */
-		Scroll<T> scroll(ScrollPosition scrollPosition);
+		Window<T> scroll(ScrollPosition scrollPosition);
 
 		/**
 		 * Get the number of matching elements. <br />

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ExecutableFindOperationSupport.java

@@ -21,7 +21,7 @@ import java.util.stream.Stream;
 
 import org.bson.Document;
 import org.springframework.dao.IncorrectResultSizeDataAccessException;
-import org.springframework.data.domain.Scroll;
+import org.springframework.data.domain.Window;
 import org.springframework.data.domain.ScrollPosition;
 import org.springframework.data.mongodb.core.query.NearQuery;
 import org.springframework.data.mongodb.core.query.Query;
@@ -141,7 +141,7 @@ class ExecutableFindOperationSupport implements ExecutableFindOperation {
 		}
 
 		@Override
-		public Scroll<T> scroll(ScrollPosition scrollPosition) {
+		public Window<T> scroll(ScrollPosition scrollPosition) {
 			return template.doScroll(query.with(scrollPosition), domainType, returnType, getCollectionName());
 		}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoOperations.java

@@ -24,7 +24,7 @@ import java.util.stream.Stream;
 
 import org.bson.Document;
 import org.springframework.data.domain.KeysetScrollPosition;
-import org.springframework.data.domain.Scroll;
+import org.springframework.data.domain.Window;
 import org.springframework.data.geo.GeoResults;
 import org.springframework.data.mongodb.core.BulkOperations.BulkMode;
 import org.springframework.data.mongodb.core.aggregation.Aggregation;
@@ -807,7 +807,7 @@ public interface MongoOperations extends FluentMongoOperations {
 	<T> List<T> find(Query query, Class<T> entityClass, String collectionName);
 
 	/**
-	 * Query for a scroll window of objects of type T from the specified collection. <br />
+	 * Query for a window window of objects of type T from the specified collection. <br />
 	 * Make sure to either set {@link Query#skip(long)} or {@link Query#with(KeysetScrollPosition)} along with
 	 * {@link Query#limit(int)} to limit large query results for efficient scrolling. <br />
 	 * Result objects are converted from the MongoDB native representation using an instance of {@see MongoConverter}.
@@ -817,16 +817,17 @@ public interface MongoOperations extends FluentMongoOperations {
 	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
 	 *          specification. Must not be {@literal null}.
-	 * @param entityType the parametrized type of the returned list.
-	 * @return the converted scroll.
+	 * @param entityType the parametrized type of the returned window.
+	 * @return the converted window.
+	 * @throws IllegalStateException if a potential {@link Query#getKeyset() KeysetScrollPosition} contains an invalid position.
 	 * @since 4.1
 	 * @see Query#with(org.springframework.data.domain.OffsetScrollPosition)
 	 * @see Query#with(org.springframework.data.domain.KeysetScrollPosition)
 	 */
-	<T> Scroll<T> scroll(Query query, Class<T> entityType);
+	<T> Window<T> scroll(Query query, Class<T> entityType);
 
 	/**
-	 * Query for a scroll of objects of type T from the specified collection. <br />
+	 * Query for a window of objects of type T from the specified collection. <br />
 	 * Make sure to either set {@link Query#skip(long)} or {@link Query#with(KeysetScrollPosition)} along with
 	 * {@link Query#limit(int)} to limit large query results for efficient scrolling. <br />
 	 * Result objects are converted from the MongoDB native representation using an instance of {@see MongoConverter}.
@@ -836,14 +837,15 @@ public interface MongoOperations extends FluentMongoOperations {
 	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
 	 *          specification. Must not be {@literal null}.
-	 * @param entityType the parametrized type of the returned list.
+	 * @param entityType the parametrized type of the returned window.
 	 * @param collectionName name of the collection to retrieve the objects from.
-	 * @return the converted scroll.
+	 * @return the converted window.
+	 * @throws IllegalStateException if a potential {@link Query#getKeyset() KeysetScrollPosition} contains an invalid position.
 	 * @since 4.1
 	 * @see Query#with(org.springframework.data.domain.OffsetScrollPosition)
 	 * @see Query#with(org.springframework.data.domain.KeysetScrollPosition)
 	 */
-	<T> Scroll<T> scroll(Query query, Class<T> entityType, String collectionName);
+	<T> Window<T> scroll(Query query, Class<T> entityType, String collectionName);
 
 	/**
 	 * Returns a document with the given id mapped onto the given class. The collection the query is ran against will be

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoTemplate.java

@@ -45,7 +45,7 @@ import org.springframework.dao.OptimisticLockingFailureException;
 import org.springframework.dao.support.PersistenceExceptionTranslator;
 import org.springframework.data.convert.EntityReader;
 import org.springframework.data.domain.OffsetScrollPosition;
-import org.springframework.data.domain.Scroll;
+import org.springframework.data.domain.Window;
 import org.springframework.data.geo.Distance;
 import org.springframework.data.geo.GeoResult;
 import org.springframework.data.geo.GeoResults;
@@ -66,7 +66,7 @@ import org.springframework.data.mongodb.core.QueryOperations.DeleteContext;
 import org.springframework.data.mongodb.core.QueryOperations.DistinctQueryContext;
 import org.springframework.data.mongodb.core.QueryOperations.QueryContext;
 import org.springframework.data.mongodb.core.QueryOperations.UpdateContext;
-import org.springframework.data.mongodb.core.ScrollUtils.KeySetCursorQuery;
+import org.springframework.data.mongodb.core.ScrollUtils.KeySetScrollQuery;
 import org.springframework.data.mongodb.core.aggregation.Aggregation;
 import org.springframework.data.mongodb.core.aggregation.AggregationOperationContext;
 import org.springframework.data.mongodb.core.aggregation.AggregationOptions;
@@ -851,7 +851,7 @@ public class MongoTemplate
 	}
 
 	@Override
-	public <T> Scroll<T> scroll(Query query, Class<T> entityType) {
+	public <T> Window<T> scroll(Query query, Class<T> entityType) {
 
 		Assert.notNull(entityType, "Entity type must not be null");
 
@@ -859,11 +859,11 @@ public class MongoTemplate
 	}
 
 	@Override
-	public <T> Scroll<T> scroll(Query query, Class<T> entityType, String collectionName) {
+	public <T> Window<T> scroll(Query query, Class<T> entityType, String collectionName) {
 		return doScroll(query, entityType, entityType, collectionName);
 	}
 
-	<T> Scroll<T> doScroll(Query query, Class<?> sourceClass, Class<T> targetClass, String collectionName) {
+	<T> Window<T> doScroll(Query query, Class<?> sourceClass, Class<T> targetClass, String collectionName) {
 
 		Assert.notNull(query, "Query must not be null");
 		Assert.notNull(collectionName, "CollectionName must not be null");
@@ -875,7 +875,7 @@ public class MongoTemplate
 
 		if (query.hasKeyset()) {
 
-			KeySetCursorQuery keysetPaginationQuery = ScrollUtils.createKeysetPaginationQuery(query,
+			KeySetScrollQuery keysetPaginationQuery = ScrollUtils.createKeysetPaginationQuery(query,
 					operations.getIdPropertyName(sourceClass));
 
 			List<T> result = doFind(collectionName, createDelegate(query), keysetPaginationQuery.query(),

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ReactiveFindOperation.java

@@ -18,7 +18,7 @@ package org.springframework.data.mongodb.core;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
-import org.springframework.data.domain.Scroll;
+import org.springframework.data.domain.Window;
 import org.springframework.data.domain.ScrollPosition;
 import org.springframework.data.geo.GeoResult;
 import org.springframework.data.mongodb.core.query.CriteriaDefinition;
@@ -98,7 +98,7 @@ public interface ReactiveFindOperation {
 		 * @see org.springframework.data.domain.OffsetScrollPosition
 		 * @see org.springframework.data.domain.KeysetScrollPosition
 		 */
-		Mono<Scroll<T>> scroll(ScrollPosition scrollPosition);
+		Mono<Window<T>> scroll(ScrollPosition scrollPosition);
 
 		/**
 		 * Get all matching elements using a {@link com.mongodb.CursorType#TailableAwait tailable cursor}. The stream will

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ReactiveFindOperationSupport.java

@@ -20,7 +20,7 @@ import reactor.core.publisher.Mono;
 
 import org.bson.Document;
 import org.springframework.dao.IncorrectResultSizeDataAccessException;
-import org.springframework.data.domain.Scroll;
+import org.springframework.data.domain.Window;
 import org.springframework.data.domain.ScrollPosition;
 import org.springframework.data.mongodb.core.CollectionPreparerSupport.ReactiveCollectionPreparerDelegate;
 import org.springframework.data.mongodb.core.query.NearQuery;
@@ -140,7 +140,7 @@ class ReactiveFindOperationSupport implements ReactiveFindOperation {
 		}
 
 		@Override
-		public Mono<Scroll<T>> scroll(ScrollPosition scrollPosition) {
+		public Mono<Window<T>> scroll(ScrollPosition scrollPosition) {
 			return template.doScroll(query.with(scrollPosition), domainType, returnType, getCollectionName());
 		}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ReactiveMongoOperations.java

@@ -26,7 +26,7 @@ import org.bson.Document;
 import org.reactivestreams.Publisher;
 import org.reactivestreams.Subscription;
 import org.springframework.data.domain.KeysetScrollPosition;
-import org.springframework.data.domain.Scroll;
+import org.springframework.data.domain.Window;
 import org.springframework.data.geo.GeoResult;
 import org.springframework.data.mongodb.ReactiveMongoDatabaseFactory;
 import org.springframework.data.mongodb.core.aggregation.Aggregation;
@@ -477,15 +477,16 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
 	 *          specification. Must not be {@literal null}.
 	 * @param entityType the parametrized type of the returned list.
-	 * @return {@link Mono} emitting the converted scroll.
+	 * @return {@link Mono} emitting the converted window.
+	 * @throws IllegalStateException if a potential {@link Query#getKeyset() KeysetScrollPosition} contains an invalid position.
 	 * @since 4.1
 	 * @see Query#with(org.springframework.data.domain.OffsetScrollPosition)
 	 * @see Query#with(org.springframework.data.domain.KeysetScrollPosition)
 	 */
-	<T> Mono<Scroll<T>> scroll(Query query, Class<T> entityType);
+	<T> Mono<Window<T>> scroll(Query query, Class<T> entityType);
 
 	/**
-	 * Query for a scroll of objects of type T from the specified collection. <br />
+	 * Query for a window of objects of type T from the specified collection. <br />
 	 * Make sure to either set {@link Query#skip(long)} or {@link Query#with(KeysetScrollPosition)} along with
 	 * {@link Query#limit(int)} to limit large query results for efficient scrolling. <br />
 	 * Result objects are converted from the MongoDB native representation using an instance of {@see MongoConverter}.
@@ -497,12 +498,13 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 *          specification. Must not be {@literal null}.
 	 * @param entityType the parametrized type of the returned list.
 	 * @param collectionName name of the collection to retrieve the objects from.
-	 * @return {@link Mono} emitting the converted scroll window.
+	 * @return {@link Mono} emitting the converted window.
+	 * @throws IllegalStateException if a potential {@link Query#getKeyset() KeysetScrollPosition} contains an invalid position.
 	 * @since 4.1
 	 * @see Query#with(org.springframework.data.domain.OffsetScrollPosition)
 	 * @see Query#with(org.springframework.data.domain.KeysetScrollPosition)
 	 */
-	<T> Mono<Scroll<T>> scroll(Query query, Class<T> entityType, String collectionName);
+	<T> Mono<Window<T>> scroll(Query query, Class<T> entityType, String collectionName);
 
 	/**
 	 * Returns a document with the given id mapped onto the given class. The collection the query is ran against will be

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ReactiveMongoTemplate.java

@@ -59,7 +59,7 @@ import org.springframework.dao.OptimisticLockingFailureException;
 import org.springframework.dao.support.PersistenceExceptionTranslator;
 import org.springframework.data.convert.EntityReader;
 import org.springframework.data.domain.OffsetScrollPosition;
-import org.springframework.data.domain.Scroll;
+import org.springframework.data.domain.Window;
 import org.springframework.data.geo.Distance;
 import org.springframework.data.geo.GeoResult;
 import org.springframework.data.geo.Metric;
@@ -80,7 +80,7 @@ import org.springframework.data.mongodb.core.QueryOperations.DeleteContext;
 import org.springframework.data.mongodb.core.QueryOperations.DistinctQueryContext;
 import org.springframework.data.mongodb.core.QueryOperations.QueryContext;
 import org.springframework.data.mongodb.core.QueryOperations.UpdateContext;
-import org.springframework.data.mongodb.core.ScrollUtils.KeySetCursorQuery;
+import org.springframework.data.mongodb.core.ScrollUtils.KeySetScrollQuery;
 import org.springframework.data.mongodb.core.aggregation.Aggregation;
 import org.springframework.data.mongodb.core.aggregation.AggregationOperationContext;
 import org.springframework.data.mongodb.core.aggregation.AggregationOptions;
@@ -830,7 +830,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	}
 
 	@Override
-	public <T> Mono<Scroll<T>> scroll(Query query, Class<T> entityType) {
+	public <T> Mono<Window<T>> scroll(Query query, Class<T> entityType) {
 
 		Assert.notNull(entityType, "Entity type must not be null");
 
@@ -838,11 +838,11 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	}
 
 	@Override
-	public <T> Mono<Scroll<T>> scroll(Query query, Class<T> entityType, String collectionName) {
+	public <T> Mono<Window<T>> scroll(Query query, Class<T> entityType, String collectionName) {
 		return doScroll(query, entityType, entityType, collectionName);
 	}
 
-	<T> Mono<Scroll<T>> doScroll(Query query, Class<?> sourceClass, Class<T> targetClass, String collectionName) {
+	<T> Mono<Window<T>> doScroll(Query query, Class<?> sourceClass, Class<T> targetClass, String collectionName) {
 
 		Assert.notNull(query, "Query must not be null");
 		Assert.notNull(collectionName, "CollectionName must not be null");
@@ -853,7 +853,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 
 		if (query.hasKeyset()) {
 
-			KeySetCursorQuery keysetPaginationQuery = ScrollUtils.createKeysetPaginationQuery(query,
+			KeySetScrollQuery keysetPaginationQuery = ScrollUtils.createKeysetPaginationQuery(query,
 					operations.getIdPropertyName(sourceClass));
 
 			Mono<List<T>> result = doFind(collectionName, ReactiveCollectionPreparerDelegate.of(query),

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ScrollUtils.java

@@ -20,17 +20,19 @@ import java.util.List;
 import java.util.Map;
 import java.util.function.IntFunction;
 
+import org.bson.BsonNull;
 import org.bson.Document;
 import org.springframework.data.domain.KeysetScrollPosition;
-import org.springframework.data.domain.Scroll;
 import org.springframework.data.domain.ScrollPosition;
+import org.springframework.data.domain.Window;
 import org.springframework.data.mongodb.core.EntityOperations.Entity;
 import org.springframework.data.mongodb.core.query.Query;
 
 /**
- * Utilities to run scroll queries and create {@link Scroll} results.
+ * Utilities to run scroll queries and create {@link Window} results.
  *
  * @author Mark Paluch
+ * @author Christoph Strobl
  * @since 4.1
  */
 class ScrollUtils {
@@ -42,7 +44,7 @@ class ScrollUtils {
 	 * @param idPropertyName
 	 * @return
 	 */
-	static KeySetCursorQuery createKeysetPaginationQuery(Query query, String idPropertyName) {
+	static KeySetScrollQuery createKeysetPaginationQuery(Query query, String idPropertyName) {
 
 		Document sortObject = query.isSorted() ? query.getSortObject() : new Document();
 		sortObject.put(idPropertyName, 1);
@@ -84,6 +86,9 @@ class ScrollUtils {
 					Object o = keysetValues.get(sortSegment);
 
 					if (j >= i) { // tail segment
+						if(o instanceof BsonNull) {
+							throw new IllegalStateException("Cannot resume from KeysetScrollPosition. Offending key: '%s' is 'null'".formatted(sortSegment));
+						}
 						sortConstraint.put(sortSegment, new Document(sortOrder == 1 ? "$gt" : "$lt", o));
 						break;
 					}
@@ -104,10 +109,10 @@ class ScrollUtils {
 			queryObject.put("$or", or);
 		}
 
-		return new KeySetCursorQuery(queryObject, fieldsObject, sortObject);
+		return new KeySetScrollQuery(queryObject, fieldsObject, sortObject);
 	}
 
-	static <T> Scroll<T> createWindow(Document sortObject, int limit, List<T> result, EntityOperations operations) {
+	static <T> Window<T> createWindow(Document sortObject, int limit, List<T> result, EntityOperations operations) {
 
 		IntFunction<KeysetScrollPosition> positionFunction = value -> {
 
@@ -121,8 +126,8 @@ class ScrollUtils {
 		return createWindow(result, limit, positionFunction);
 	}
 
-	static <T> Scroll<T> createWindow(List<T> result, int limit, IntFunction<? extends ScrollPosition> positionFunction) {
-		return Scroll.from(getSubList(result, limit), positionFunction, hasMoreElements(result, limit));
+	static <T> Window<T> createWindow(List<T> result, int limit, IntFunction<? extends ScrollPosition> positionFunction) {
+		return Window.from(getSubList(result, limit), positionFunction, hasMoreElements(result, limit));
 	}
 
 	static boolean hasMoreElements(List<?> result, int limit) {
@@ -138,7 +143,7 @@ class ScrollUtils {
 		return result;
 	}
 
-	record KeySetCursorQuery(Document query, Document fields, Document sort) {
+	record KeySetScrollQuery(Document query, Document fields, Document sort) {
 
 	}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/support/QuerydslMongoPredicateExecutor.java

@@ -25,7 +25,7 @@ import org.bson.Document;
 import org.springframework.dao.IncorrectResultSizeDataAccessException;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
-import org.springframework.data.domain.Scroll;
+import org.springframework.data.domain.Window;
 import org.springframework.data.domain.ScrollPosition;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.mongodb.core.MongoOperations;
@@ -259,7 +259,7 @@ public class QuerydslMongoPredicateExecutor<T> extends QuerydslPredicateExecutor
 		}
 
 		@Override
-		public Scroll<T> scroll(ScrollPosition scrollPosition) {
+		public Window<T> scroll(ScrollPosition scrollPosition) {
 			return createQuery().scroll(scrollPosition);
 		}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/support/ReactiveQuerydslMongoPredicateExecutor.java

@@ -26,7 +26,7 @@ import org.bson.Document;
 import org.reactivestreams.Publisher;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
-import org.springframework.data.domain.Scroll;
+import org.springframework.data.domain.Window;
 import org.springframework.data.domain.ScrollPosition;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.mongodb.core.ReactiveMongoOperations;
@@ -227,7 +227,7 @@ public class ReactiveQuerydslMongoPredicateExecutor<T> extends QuerydslPredicate
 		}
 
 		@Override
-		public Mono<Scroll<T>> scroll(ScrollPosition scrollPosition) {
+		public Mono<Window<T>> scroll(ScrollPosition scrollPosition) {
 			return createQuery().scroll(scrollPosition);
 		}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/support/ReactiveSpringDataMongodbQuery.java

@@ -26,7 +26,7 @@ import java.util.function.Consumer;
 import org.bson.Document;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
-import org.springframework.data.domain.Scroll;
+import org.springframework.data.domain.Window;
 import org.springframework.data.domain.ScrollPosition;
 import org.springframework.data.mongodb.core.MongoOperations;
 import org.springframework.data.mongodb.core.ReactiveFindOperation;
@@ -91,7 +91,7 @@ class ReactiveSpringDataMongodbQuery<K> extends SpringDataMongodbQuerySupport<Re
 		return createQuery().flatMapMany(it -> find.matching(it).all());
 	}
 
-	Mono<Scroll<K>> scroll(ScrollPosition scrollPosition) {
+	Mono<Window<K>> scroll(ScrollPosition scrollPosition) {
 		return createQuery().flatMap(it -> find.matching(it).scroll(scrollPosition));
 	}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/support/SimpleMongoRepository.java

@@ -32,7 +32,7 @@ import org.springframework.data.domain.Example;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageImpl;
 import org.springframework.data.domain.Pageable;
-import org.springframework.data.domain.Scroll;
+import org.springframework.data.domain.Window;
 import org.springframework.data.domain.ScrollPosition;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.mongodb.core.ExecutableFindOperation;
@@ -392,7 +392,7 @@ public class SimpleMongoRepository<T, ID> implements MongoRepository<T, ID> {
 		}
 
 		@Override
-		public Scroll<T> scroll(ScrollPosition scrollPosition) {
+		public Window<T> scroll(ScrollPosition scrollPosition) {
 			return createQuery().scroll(scrollPosition);
 		}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/support/SimpleReactiveMongoRepository.java

@@ -34,7 +34,7 @@ import org.springframework.dao.OptimisticLockingFailureException;
 import org.springframework.data.domain.Example;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
-import org.springframework.data.domain.Scroll;
+import org.springframework.data.domain.Window;
 import org.springframework.data.domain.ScrollPosition;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.mongodb.core.ReactiveFindOperation;
@@ -436,7 +436,7 @@ public class SimpleReactiveMongoRepository<T, ID extends Serializable> implement
 		}
 
 		@Override
-		public Mono<Scroll<T>> scroll(ScrollPosition scrollPosition) {
+		public Mono<Window<T>> scroll(ScrollPosition scrollPosition) {
 			return createQuery().scroll(scrollPosition);
 		}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/support/SpringDataMongodbQuery.java

@@ -25,7 +25,7 @@ import org.bson.Document;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageImpl;
 import org.springframework.data.domain.Pageable;
-import org.springframework.data.domain.Scroll;
+import org.springframework.data.domain.Window;
 import org.springframework.data.domain.ScrollPosition;
 import org.springframework.data.mongodb.core.ExecutableFindOperation;
 import org.springframework.data.mongodb.core.MongoOperations;
@@ -133,12 +133,12 @@ public class SpringDataMongodbQuery<T> extends SpringDataMongodbQuerySupport<Spr
 		}
 	}
 
-	public Scroll<T> scroll(ScrollPosition scrollPosition) {
+	public Window<T> scroll(ScrollPosition scrollPosition) {
 
 		try {
 			return find.matching(createQuery()).scroll(scrollPosition);
 		} catch (RuntimeException e) {
-			return handleException(e, Scroll.from(Collections.emptyList(), value -> {
+			return handleException(e, Window.from(Collections.emptyList(), value -> {
 				throw new UnsupportedOperationException();
 			}));
 		}

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/MongoTemplateScrollTests.java

@@ -38,9 +38,9 @@ import org.springframework.data.annotation.PersistenceCreator;
 import org.springframework.data.auditing.IsNewAwareAuditingHandler;
 import org.springframework.data.domain.KeysetScrollPosition;
 import org.springframework.data.domain.OffsetScrollPosition;
-import org.springframework.data.domain.Scroll;
 import org.springframework.data.domain.ScrollPosition;
 import org.springframework.data.domain.Sort;
+import org.springframework.data.domain.Window;
 import org.springframework.data.mapping.context.PersistentEntities;
 import org.springframework.data.mongodb.core.MongoTemplateTests.PersonWithIdPropertyOfTypeUUIDListener;
 import org.springframework.data.mongodb.core.query.Query;
@@ -51,9 +51,10 @@ import org.springframework.data.mongodb.test.util.MongoTestTemplate;
 import com.mongodb.client.MongoClient;
 
 /**
- * Integration tests for {@link Scroll} queries.
+ * Integration tests for {@link org.springframework.data.domain.Window} queries.
  *
  * @author Mark Paluch
+ * @author Christoph Strobl
  */
 @ExtendWith(MongoClientExtension.class)
 class MongoTemplateScrollTests {
@@ -94,7 +95,7 @@ class MongoTemplateScrollTests {
 		template.remove(WithNestedDocument.class).all();
 	}
 
-	@Test
+	@Test // GH-4308
 	void shouldUseKeysetScrollingWithNestedSort() {
 
 		WithNestedDocument john20 = new WithNestedDocument(null, "John", 120, new WithNestedDocument("John", 20),
@@ -110,20 +111,55 @@ class MongoTemplateScrollTests {
 				.limit(2);
 		q.with(KeysetScrollPosition.initial());
 
-		Scroll<WithNestedDocument> scroll = template.scroll(q, WithNestedDocument.class);
+		Window<WithNestedDocument> scroll = template.scroll(q, WithNestedDocument.class);
 
 		assertThat(scroll.hasNext()).isTrue();
 		assertThat(scroll.isLast()).isFalse();
 		assertThat(scroll).hasSize(2);
 		assertThat(scroll).containsOnly(john20, john40);
 
-		scroll = template.scroll(q.with(scroll.lastPosition()), WithNestedDocument.class);
+		scroll = template.scroll(q.with(scroll.positionAt(scroll.size()-1)), WithNestedDocument.class);
 
 		assertThat(scroll.hasNext()).isFalse();
 		assertThat(scroll.isLast()).isTrue();
 		assertThat(scroll).hasSize(1);
 		assertThat(scroll).containsOnly(john41);
+	}
+
+	@Test // GH-4308
+	void shouldErrorOnNullValueForQuery() {
+
+		WithNestedDocument john20 = new WithNestedDocument(null, "John", 120, new WithNestedDocument("John", 20),
+				new Document("name", "bar"));
+		WithNestedDocument john40 = new WithNestedDocument(null, "John", 140, new WithNestedDocument("John", 41),
+				new Document());
+		WithNestedDocument john41 = new WithNestedDocument(null, "John", 140, new WithNestedDocument("John", 41),
+				new Document());
+		WithNestedDocument john42 = new WithNestedDocument(null, "John", 140, new WithNestedDocument("John", 41),
+				new Document());
+		WithNestedDocument john43 = new WithNestedDocument(null, "John", 140, new WithNestedDocument("John", 41),
+				new Document());
+		WithNestedDocument john44 = new WithNestedDocument(null, "John", 141, new WithNestedDocument("John", 41),
+				new Document("name", "foo"));
+
+		template.insertAll(Arrays.asList(john20, john40, john41, john42, john43, john44));
+
+		Query q = new Query(where("name").regex("J.*")).with(Sort.by("nested.name", "nested.age", "document.name"))
+				.limit(2);
+		q.with(KeysetScrollPosition.initial());
+
+		Window<WithNestedDocument> scroll = template.scroll(q, WithNestedDocument.class);
+
+		assertThat(scroll.hasNext()).isTrue();
+		assertThat(scroll.isLast()).isFalse();
+		assertThat(scroll).hasSize(2);
+		assertThat(scroll).containsOnly(john20, john40);
+
+		ScrollPosition startAfter = scroll.positionAt(scroll.size()-1);
 
+		assertThatExceptionOfType(IllegalStateException.class)
+				.isThrownBy(() -> template.scroll(q.with(startAfter), WithNestedDocument.class))
+				.withMessageContaining("document.name");
 	}
 
 	@ParameterizedTest // GH-4308
@@ -142,14 +178,14 @@ class MongoTemplateScrollTests {
 		Query q = new Query(where("firstName").regex("J.*")).with(Sort.by("firstName", "age")).limit(2);
 		q.with(scrollPosition);
 
-		Scroll<T> scroll = template.scroll(q, resultType, "person");
+		Window<T> scroll = template.scroll(q, resultType, "person");
 
 		assertThat(scroll.hasNext()).isTrue();
 		assertThat(scroll.isLast()).isFalse();
 		assertThat(scroll).hasSize(2);
 		assertThat(scroll).containsOnly(assertionConverter.apply(jane_20), assertionConverter.apply(jane_40));
 
-		scroll = template.scroll(q.with(scroll.lastPosition()).limit(3), resultType, "person");
+		scroll = template.scroll(q.with(scroll.positionAt(scroll.size()-1)).limit(3), resultType, "person");
 
 		assertThat(scroll.hasNext()).isTrue();
 		assertThat(scroll.isLast()).isFalse();
@@ -157,7 +193,7 @@ class MongoTemplateScrollTests {
 		assertThat(scroll).contains(assertionConverter.apply(jane_42), assertionConverter.apply(john20));
 		assertThat(scroll).containsAnyOf(assertionConverter.apply(john40_1), assertionConverter.apply(john40_2));
 
-		scroll = template.scroll(q.with(scroll.lastPosition()).limit(1), resultType, "person");
+		scroll = template.scroll(q.with(scroll.positionAt(scroll.size()-1)).limit(1), resultType, "person");
 
 		assertThat(scroll.hasNext()).isFalse();
 		assertThat(scroll.isLast()).isTrue();

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/ReactiveMongoTemplateScrollTests.java

@@ -35,7 +35,7 @@ import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.support.GenericApplicationContext;
 import org.springframework.data.domain.KeysetScrollPosition;
 import org.springframework.data.domain.OffsetScrollPosition;
-import org.springframework.data.domain.Scroll;
+import org.springframework.data.domain.Window;
 import org.springframework.data.domain.ScrollPosition;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.mongodb.core.query.Query;
@@ -46,7 +46,7 @@ import org.springframework.data.mongodb.test.util.ReactiveMongoTestTemplate;
 import com.mongodb.reactivestreams.client.MongoClient;
 
 /**
- * Integration tests for {@link Scroll} queries.
+ * Integration tests for {@link Window} queries.
  *
  * @author Mark Paluch
  */
@@ -100,14 +100,14 @@ class ReactiveMongoTemplateScrollTests {
 		Query q = new Query(where("firstName").regex("J.*")).with(Sort.by("firstName", "age")).limit(2);
 		q.with(scrollPosition);
 
-		Scroll<T> scroll = template.scroll(q, resultType, "person").block(Duration.ofSeconds(10));
+		Window<T> scroll = template.scroll(q, resultType, "person").block(Duration.ofSeconds(10));
 
 		assertThat(scroll.hasNext()).isTrue();
 		assertThat(scroll.isLast()).isFalse();
 		assertThat(scroll).hasSize(2);
 		assertThat(scroll).containsOnly(assertionConverter.apply(jane_20), assertionConverter.apply(jane_40));
 
-		scroll = template.scroll(q.limit(3).with(scroll.lastPosition()), resultType, "person")
+		scroll = template.scroll(q.limit(3).with(scroll.positionAt(scroll.size() - 1)), resultType, "person")
 				.block(Duration.ofSeconds(10));
 
 		assertThat(scroll.hasNext()).isTrue();
@@ -116,7 +116,7 @@ class ReactiveMongoTemplateScrollTests {
 		assertThat(scroll).contains(assertionConverter.apply(jane_42), assertionConverter.apply(john20));
 		assertThat(scroll).containsAnyOf(assertionConverter.apply(john40_1), assertionConverter.apply(john40_2));
 
-		scroll = template.scroll(q.limit(1).with(scroll.lastPosition()), resultType, "person")
+		scroll = template.scroll(q.limit(1).with(scroll.positionAt(scroll.size() - 1)), resultType, "person")
 				.block(Duration.ofSeconds(10));
 
 		assertThat(scroll.hasNext()).isFalse();

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

@@ -205,7 +205,7 @@ public abstract class AbstractPersonRepositoryIntegrationTests implements Dirtie
 	@Test // GH-4308
 	void appliesScrollPositionCorrectly() {
 
-		Scroll<Person> page = repository.findTop2ByLastnameLikeOrderByLastnameAscFirstnameAsc("*a*",
+		Window<Person> page = repository.findTop2ByLastnameLikeOrderByLastnameAscFirstnameAsc("*a*",
 				KeysetScrollPosition.initial());
 
 		assertThat(page.isLast()).isFalse();
@@ -216,7 +216,7 @@ public abstract class AbstractPersonRepositoryIntegrationTests implements Dirtie
 	@Test // GH-4308
 	void appliesScrollPositionWithProjectionCorrectly() {
 
-		Scroll<PersonSummaryDto> page = repository.findCursorProjectionByLastnameLike("*a*",
+		Window<PersonSummaryDto> page = repository.findCursorProjectionByLastnameLike("*a*",
 				PageRequest.of(0, 2, Sort.by(Direction.ASC, "lastname", "firstname")));
 
 		assertThat(page.isLast()).isFalse();
@@ -956,12 +956,12 @@ public abstract class AbstractPersonRepositoryIntegrationTests implements Dirtie
 	@Test // DATAMONGO-969
 	void shouldScrollPersonsWhenUsingQueryDslPerdicatedOnIdProperty() {
 
-		Scroll<Person> scroll = repository.findBy(person.id.in(asList(dave.id, carter.id, boyd.id)), //
+		Window<Person> scroll = repository.findBy(person.id.in(asList(dave.id, carter.id, boyd.id)), //
 				q -> q.limit(2).sortBy(Sort.by("firstname")).scroll(KeysetScrollPosition.initial()));
 
 		assertThat(scroll).containsExactly(boyd, carter);
 
-		ScrollPosition resumeFrom = scroll.lastPosition();
+		ScrollPosition resumeFrom = scroll.positionAt(scroll.size() - 1);
 		scroll = repository.findBy(person.id.in(asList(dave.id, carter.id, boyd.id)), //
 				q -> q.limit(2).sortBy(Sort.by("firstname")).scroll(resumeFrom));
 
@@ -1185,14 +1185,14 @@ public abstract class AbstractPersonRepositoryIntegrationTests implements Dirtie
 		ReflectionTestUtils.setField(sample, "createdAt", null);
 		ReflectionTestUtils.setField(sample, "email", null);
 
-		Scroll<Person> result = repository.findBy(
+		Window<Person> result = repository.findBy(
 				Example.of(sample, ExampleMatcher.matching().withMatcher("lastname", GenericPropertyMatcher::startsWith)),
 				q -> q.limit(2).sortBy(Sort.by("firstname")).scroll(KeysetScrollPosition.initial()));
 
 		assertThat(result).containsOnly(dave, leroi);
 		assertThat(result.hasNext()).isTrue();
 
-		ScrollPosition position = result.lastPosition();
+		ScrollPosition position = result.positionAt(result.size() - 1);
 		result = repository.findBy(
 				Example.of(sample, ExampleMatcher.matching().withMatcher("lastname", GenericPropertyMatcher::startsWith)),
 				q -> q.limit(2).sortBy(Sort.by("firstname")).scroll(position));

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

@@ -23,11 +23,11 @@ import java.util.UUID;
 import java.util.regex.Pattern;
 import java.util.stream.Stream;
 
-import org.springframework.data.domain.KeysetScrollPosition;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Range;
-import org.springframework.data.domain.Scroll;
+import org.springframework.data.domain.Window;
+import org.springframework.data.domain.ScrollPosition;
 import org.springframework.data.domain.Slice;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.geo.Box;
@@ -123,8 +123,8 @@ public interface PersonRepository extends MongoRepository<Person, String>, Query
 	 * @param scrollPosition
 	 * @return
 	 */
-	Scroll<Person> findTop2ByLastnameLikeOrderByLastnameAscFirstnameAsc(String lastname,
-			KeysetScrollPosition scrollPosition);
+	Window<Person> findTop2ByLastnameLikeOrderByLastnameAscFirstnameAsc(String lastname,
+			ScrollPosition scrollPosition);
 
 	/**
 	 * Returns a scroll of {@link Person}s applying projections with a lastname matching the given one (*-wildcards
@@ -134,7 +134,7 @@ public interface PersonRepository extends MongoRepository<Person, String>, Query
 	 * @param pageable
 	 * @return
 	 */
-	Scroll<PersonSummaryDto> findCursorProjectionByLastnameLike(String lastname, Pageable pageable);
+	Window<PersonSummaryDto> findCursorProjectionByLastnameLike(String lastname, Pageable pageable);
 
 	/**
 	 * Returns a page of {@link Person}s with a lastname matching the given one (*-wildcards supported).

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

@@ -50,10 +50,10 @@ import org.springframework.dao.IncorrectResultSizeDataAccessException;
 import org.springframework.data.domain.KeysetScrollPosition;
 import org.springframework.data.domain.PageRequest;
 import org.springframework.data.domain.Pageable;
-import org.springframework.data.domain.Scroll;
 import org.springframework.data.domain.ScrollPosition;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.domain.Sort.Direction;
+import org.springframework.data.domain.Window;
 import org.springframework.data.geo.Circle;
 import org.springframework.data.geo.Distance;
 import org.springframework.data.geo.GeoResult;
@@ -293,15 +293,15 @@ class ReactiveMongoRepositoryTests implements DirtiesStateExtension.StateFunctio
 	@Test // GH-4308
 	void appliesScrollingCorrectly() {
 
-		Scroll<Person> scroll = repository
+		Window<Person> scroll = repository
 				.findTop2ByLastnameLikeOrderByFirstnameAscLastnameAsc("*", KeysetScrollPosition.initial()).block();
 
 		assertThat(scroll).hasSize(2);
 		assertThat(scroll).containsSequence(alicia, boyd);
 		assertThat(scroll.isLast()).isFalse();
 
-		Scroll<Person> nextScroll = repository
-				.findTop2ByLastnameLikeOrderByFirstnameAscLastnameAsc("*", scroll.lastPosition()).block();
+		Window<Person> nextScroll = repository
+				.findTop2ByLastnameLikeOrderByFirstnameAscLastnameAsc("*", scroll.positionAt(scroll.size() - 1)).block();
 
 		assertThat(nextScroll).hasSize(2);
 		assertThat(nextScroll).containsSequence(carter, dave);
@@ -474,7 +474,7 @@ class ReactiveMongoRepositoryTests implements DirtiesStateExtension.StateFunctio
 	@Test // GH-4308
 	void shouldScrollWithId() {
 
-		List<Scroll<Person>> capture = new ArrayList<>();
+		List<Window<Person>> capture = new ArrayList<>();
 		repository.findBy(person.id.in(Arrays.asList(dave.id, carter.id, boyd.id)), //
 				q -> q.limit(2).sortBy(Sort.by("firstname")).scroll(KeysetScrollPosition.initial())) //
 				.as(StepVerifier::create) //
@@ -482,10 +482,10 @@ class ReactiveMongoRepositoryTests implements DirtiesStateExtension.StateFunctio
 					assertThat(actual).hasSize(2).containsExactly(boyd, carter);
 				}).verifyComplete();
 
-		Scroll<Person> scroll = capture.get(0);
+		Window<Person> scroll = capture.get(0);
 
 		repository.findBy(person.id.in(Arrays.asList(dave.id, carter.id, boyd.id)), //
-				q -> q.limit(2).sortBy(Sort.by("firstname")).scroll(scroll.lastPosition())) //
+				q -> q.limit(2).sortBy(Sort.by("firstname")).scroll(scroll.positionAt(scroll.size() - 1))) //
 				.as(StepVerifier::create) //
 				.recordWith(() -> capture).assertNext(actual -> {
 					assertThat(actual).containsOnly(dave);
@@ -768,10 +768,10 @@ class ReactiveMongoRepositoryTests implements DirtiesStateExtension.StateFunctio
 		@Query("{ lastname: { $in: ?0 }, age: { $gt : ?1 } }")
 		Flux<Person> findStringQuery(Flux<String> lastname, Mono<Integer> age);
 
-		Mono<Scroll<Person>> findTop2ByLastnameLikeOrderByFirstnameAscLastnameAsc(String lastname,
+		Mono<Window<Person>> findTop2ByLastnameLikeOrderByFirstnameAscLastnameAsc(String lastname,
 				ScrollPosition scrollPosition);
 
-		Mono<Scroll<PersonSummaryDto>> findCursorProjectionByLastnameLike(String lastname, Pageable pageable);
+		Mono<Window<PersonSummaryDto>> findCursorProjectionByLastnameLike(String lastname, Pageable pageable);
 
 		Flux<Person> findByLocationWithin(Circle circle);