Initial draft for cursor window queries.

Author: mp911de

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

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core;
+
+import java.util.List;
+
+import org.springframework.data.domain.CursorRequest;
+import org.springframework.data.domain.CursorWindow;
+
+/**
+ * @author Mark Paluch
+ */
+class CursorUtils {
+
+	static boolean hasMoreElements(CursorRequest request, List<?> result) {
+		return !result.isEmpty() && result.size() > request.getSize();
+	}
+
+	static boolean isLast(CursorRequest request, List<?> result) {
+		return !hasMoreElements(request, result);
+	}
+
+	static <T> List<T> getSubList(CursorRequest request, List<T> result) {
+
+		if (result.size() > request.getSize()) {
+			return result.subList(0, request.getSize());
+		}
+
+		return result;
+	}
+
+	public static <T> CursorWindow<T> createWindow(CursorRequest cursorRequest, List<T> result) {
+		return CursorWindow.from(cursorRequest.withLast(isLast(cursorRequest, result)), getSubList(cursorRequest, result));
+	}
+}

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

@@ -17,13 +17,16 @@
 
 import java.util.Collection;
 import java.util.Iterator;
+import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.Optional;
 
 import org.bson.Document;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.dao.InvalidDataAccessApiUsageException;
 import org.springframework.data.convert.CustomConversions;
+import org.springframework.data.domain.Sort;
+import org.springframework.data.domain.Sort.Order;
 import org.springframework.data.mapping.IdentifierAccessor;
 import org.springframework.data.mapping.MappingException;
 import org.springframework.data.mapping.PersistentEntity;
@@ -44,6 +47,7 @@
 import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.data.mongodb.core.timeseries.Granularity;
 import org.springframework.data.mongodb.core.validation.Validator;
+import org.springframework.data.mongodb.util.BsonUtils;
 import org.springframework.data.projection.EntityProjection;
 import org.springframework.data.projection.EntityProjectionIntrospector;
 import org.springframework.data.projection.ProjectionFactory;
@@ -450,6 +454,9 @@ default boolean isVersionedEntity() {
 		 * @since 2.1.2
 		 */
 		boolean isNew();
+
+		Map<String, Object> extractKeys(Sort sort);
+
 	}
 
 	/**
@@ -563,6 +570,19 @@ public T getBean() {
 		public boolean isNew() {
 			return map.get(ID_FIELD) != null;
 		}
+
+		@Override
+		public Map<String, Object> extractKeys(Sort sort) {
+
+			Map<String, Object> keyset = new LinkedHashMap<>();
+			keyset.put(ID_FIELD, getId());
+
+			for (Order order : sort) {
+				keyset.put(order.getProperty(), BsonUtils.resolveValue(map, order.getProperty()));
+			}
+
+			return keyset;
+		}
 	}
 
 	private static class SimpleMappedEntity<T extends Map<String, Object>> extends UnmappedEntity<T> {
@@ -697,6 +717,22 @@ public T getBean() {
 		public boolean isNew() {
 			return entity.isNew(propertyAccessor.getBean());
 		}
+
+		@Override
+		public Map<String, Object> extractKeys(Sort sort) {
+
+			Map<String, Object> keyset = new LinkedHashMap<>();
+			keyset.put(entity.getRequiredIdProperty().getName(), getId());
+
+			for (Order order : sort) {
+
+				// TODO: make this work for nested properties
+				MongoPersistentProperty persistentProperty = entity.getRequiredPersistentProperty(order.getProperty());
+				keyset.put(order.getProperty(), propertyAccessor.getProperty(persistentProperty));
+			}
+
+			return keyset;
+		}
 	}
 
 	private static class AdaptibleMappedEntity<T> extends MappedEntity<T> implements AdaptibleEntity<T> {

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

@@ -23,6 +23,8 @@
 import java.util.stream.Stream;
 
 import org.bson.Document;
+import org.springframework.data.domain.CursorRequest;
+import org.springframework.data.domain.CursorWindow;
 import org.springframework.data.geo.GeoResults;
 import org.springframework.data.mongodb.core.BulkOperations.BulkMode;
 import org.springframework.data.mongodb.core.aggregation.Aggregation;
@@ -319,7 +321,8 @@ default MongoCollection<Document> createView(String name, Class<?> source, Aggre
 	 * @param options additional settings to apply when creating the view. Can be {@literal null}.
 	 * @since 4.0
 	 */
-	MongoCollection<Document> createView(String name, Class<?> source, AggregationPipeline pipeline, @Nullable ViewOptions options);
+	MongoCollection<Document> createView(String name, Class<?> source, AggregationPipeline pipeline,
+			@Nullable ViewOptions options);
 
 	/**
 	 * Create a view with the provided name. The view content is defined by the {@link AggregationPipeline pipeline} on
@@ -331,7 +334,8 @@ default MongoCollection<Document> createView(String name, Class<?> source, Aggre
 	 * @param options additional settings to apply when creating the view. Can be {@literal null}.
 	 * @since 4.0
 	 */
-	MongoCollection<Document> createView(String name, String source, AggregationPipeline pipeline, @Nullable ViewOptions options);
+	MongoCollection<Document> createView(String name, String source, AggregationPipeline pipeline,
+			@Nullable ViewOptions options);
 
 	/**
 	 * A set of collection names.
@@ -466,6 +470,38 @@ default MongoCollection<Document> createView(String name, Class<?> source, Aggre
 	 */
 	<T> List<T> findAll(Class<T> entityClass, String collectionName);
 
+	/**
+	 * Query for a cursor window of objects of type T from the specified collection. <br />
+	 * The object is converted from the MongoDB native representation using an instance of {@see MongoConverter}. Unless
+	 * configured otherwise, an instance of {@link MappingMongoConverter} will be used. <br />
+	 * If your collection does not contain a homogeneous collection of types, this operation will not be an efficient way
+	 * to map objects since the test for class type is done in the client and not on the server.
+	 *
+	 * @param cursorRequest the cursor request.
+	 * @param entityType the parametrized type of the returned list.
+	 * @param collectionName name of the collection to retrieve the objects from.
+	 * @return the converted cursor window.
+	 * @see org.springframework.data.domain.OffsetCursorRequest
+	 * @see org.springframework.data.domain.KeysetCursorRequest
+	 */
+	<T> CursorWindow<T> findWindow(CursorRequest cursorRequest, Query query, Class<T> entityTypee);
+
+	/**
+	 * Query for a cursor window of objects of type T from the specified collection. <br />
+	 * The object is converted from the MongoDB native representation using an instance of {@see MongoConverter}. Unless
+	 * configured otherwise, an instance of {@link MappingMongoConverter} will be used. <br />
+	 * If your collection does not contain a homogeneous collection of types, this operation will not be an efficient way
+	 * to map objects since the test for class type is done in the client and not on the server.
+	 *
+	 * @param cursorRequest the cursor request.
+	 * @param entityType the parametrized type of the returned list.
+	 * @param collectionName name of the collection to retrieve the objects from.
+	 * @return the converted cursor window.
+	 * @see org.springframework.data.domain.OffsetCursorRequest
+	 * @see org.springframework.data.domain.KeysetCursorRequest
+	 */
+	<T> CursorWindow<T> findWindow(CursorRequest cursorRequest, Query query, Class<T> entityType, String collectionName);
+
 	/**
 	 * Execute an aggregation operation. The raw results will be mapped to the given entity class. The name of the
 	 * inputCollection is derived from the inputType of the aggregation.
@@ -1175,7 +1211,7 @@ <S, T> T findAndReplace(Query query, S replacement, FindAndReplaceOptions option
 	 * @param entityClass class that determines the collection to use. Must not be {@literal null}.
 	 * @return the count of matching documents.
 	 * @throws org.springframework.data.mapping.MappingException if the collection name cannot be
-	 * 	  {@link #getCollectionName(Class) derived} from the given type.
+	 *           {@link #getCollectionName(Class) derived} from the given type.
 	 * @see #exactCount(Query, Class)
 	 * @see #estimatedCount(Class)
 	 */