DATAMONGO-765 - Support skip and limit parameters in GridFsTemplate and ReactiveGridFsTemplate.

Leverage `skip` and `limit` methods exposed in `GridFSFindIterable` to support limiting and skipping results.
In particular these changes allow the `find(Query)` method to correctly consider parameters of a page request.

Original pull request: #806.

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/gridfs/GridFsTemplate.java

@@ -23,7 +23,6 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
 
-import org.bson.BsonObjectId;
 import org.bson.Document;
 import org.bson.types.ObjectId;
 import org.springframework.core.io.support.ResourcePatternResolver;
@@ -51,6 +50,7 @@ import com.mongodb.client.gridfs.model.GridFSFile;
  * @author Mark Paluch
  * @author Hartmut Lang
  * @author Niklas Helge Hanft
+ * @author Denis Zavedeev
  */
 public class GridFsTemplate extends GridFsOperationsSupport implements GridFsOperations, ResourcePatternResolver {
 
@@ -166,7 +166,14 @@ public class GridFsTemplate extends GridFsOperationsSupport implements GridFsOpe
 		Document queryObject = getMappedQuery(query.getQueryObject());
 		Document sortObject = getMappedQuery(query.getSortObject());
 
-		return getGridFs().find(queryObject).sort(sortObject);
+		GridFSFindIterable iterable = getGridFs().find(queryObject).sort(sortObject);
+		if (query.getSkip() > 0) {
+			iterable = iterable.skip(Math.toIntExact(query.getSkip()));
+		}
+		if (query.getLimit() > 0) {
+			iterable = iterable.limit(query.getLimit());
+		}
+		return iterable;
 	}
 
 	/*

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/gridfs/ReactiveGridFsTemplate.java

@@ -50,6 +50,7 @@ import com.mongodb.reactivestreams.client.gridfs.GridFSFindPublisher;
  *
  * @author Mark Paluch
  * @author Nick Stolwijk
+ * @author Denis Zavedeev
  * @since 2.2
  */
 public class ReactiveGridFsTemplate extends GridFsOperationsSupport implements ReactiveGridFsOperations {
@@ -261,7 +262,12 @@ public class ReactiveGridFsTemplate extends GridFsOperationsSupport implements R
 		Document sortObject = getMappedQuery(query.getSortObject());
 
 		GridFSFindPublisher publisherToUse = getGridFs().find(queryObject).sort(sortObject);
-
+		if (query.getLimit() > 0) {
+			publisherToUse = publisherToUse.limit(query.getLimit());
+		}
+		if (query.getSkip() > 0) {
+			publisherToUse = publisherToUse.skip(Math.toIntExact(query.getSkip()));
+		}
 		Integer cursorBatchSize = query.getMeta().getCursorBatchSize();
 		if (cursorBatchSize != null) {
 			publisherToUse = publisherToUse.batchSize(cursorBatchSize);

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/gridfs/GridFsTemplateIntegrationTests.java

@@ -20,6 +20,7 @@ import static org.springframework.data.mongodb.core.query.Criteria.*;
 import static org.springframework.data.mongodb.core.query.Query.*;
 import static org.springframework.data.mongodb.gridfs.GridFsCriteria.*;
 
+import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.LinkedHashMap;
@@ -27,6 +28,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.UUID;
+import java.util.stream.Stream;
 
 import org.bson.BsonObjectId;
 import org.bson.Document;
@@ -38,6 +40,7 @@ import org.junit.runner.RunWith;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.Resource;
+import org.springframework.data.domain.PageRequest;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.domain.Sort.Direction;
 import org.springframework.data.mongodb.core.SimpleMongoDbFactory;
@@ -61,6 +64,7 @@ import com.mongodb.gridfs.GridFSInputFile;
  * @author Martin Baumgartner
  * @author Hartmut Lang
  * @author Mark Paluch
+ * @author Denis Zavedeev
  */
 @RunWith(SpringJUnit4ClassRunner.class)
 @ContextConfiguration("classpath:gridfs/gridfs.xml")
@@ -289,6 +293,23 @@ public class GridFsTemplateIntegrationTests {
 		}
 	}
 
+	@Test // DATAMONGO-2411
+	public void considersSkipLimitWhenQueryingFiles() {
+		Stream.of( //
+				"a", "aa", "aaa", //
+				"b", "bb", "bb", //
+				"c", "cc", "ccc", //
+				"d", "dd", "ddd") //
+				.forEach(filename -> operations.store(new ByteArrayInputStream(new byte[0]), filename));
+
+		PageRequest pageRequest = PageRequest.of(2, 3, Direction.ASC, "filename");
+		List<String> filenames = operations.find(new Query().with(pageRequest)) //
+				.map(GridFSFile::getFilename) //
+				.into(new ArrayList<>());
+
+		assertThat(filenames).containsExactly("c", "cc", "ccc");
+	}
+
 	class Metadata {
 		String version;
 	}

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/gridfs/ReactiveGridFsTemplateTests.java

@@ -21,6 +21,7 @@ import static org.springframework.data.mongodb.core.query.Query.*;
 import static org.springframework.data.mongodb.gridfs.GridFsCriteria.*;
 
 import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 
 import java.io.IOException;
@@ -36,10 +37,14 @@ import org.junit.runner.RunWith;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.Resource;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.core.io.buffer.DataBufferFactory;
 import org.springframework.core.io.buffer.DataBufferUtils;
 import org.springframework.core.io.buffer.DefaultDataBuffer;
 import org.springframework.core.io.buffer.DefaultDataBufferFactory;
 import org.springframework.dao.IncorrectResultSizeDataAccessException;
+import org.springframework.data.domain.PageRequest;
+import org.springframework.data.domain.Sort;
 import org.springframework.data.mongodb.ReactiveMongoDatabaseFactory;
 import org.springframework.data.mongodb.core.SimpleMongoDbFactory;
 import org.springframework.data.mongodb.core.convert.MongoConverter;
@@ -48,6 +53,7 @@ import org.springframework.test.context.ContextConfiguration;
 import org.springframework.test.context.junit4.SpringRunner;
 import org.springframework.util.StreamUtils;
 
+import com.mongodb.client.gridfs.model.GridFSFile;
 import com.mongodb.gridfs.GridFS;
 import com.mongodb.gridfs.GridFSInputFile;
 import com.mongodb.internal.HexUtils;
@@ -60,6 +66,7 @@ import com.mongodb.reactivestreams.client.gridfs.helpers.AsyncStreamHelper;
  * @author Mark Paluch
  * @author Christoph Strobl
  * @author Nick Stolwijk
+ * @author Denis Zavedeev
  */
 @RunWith(SpringRunner.class)
 @ContextConfiguration("classpath:gridfs/reactive-gridfs.xml")
@@ -282,6 +289,26 @@ public class ReactiveGridFsTemplateTests {
 				.verifyComplete();
 	}
 
+	@Test // DATAMONGO-2411
+	public void considersSkipLimitWhenQueryingFiles() {
+		DataBufferFactory bufferFactory = new DefaultDataBufferFactory();
+		DataBuffer buffer = bufferFactory.allocateBuffer(0);
+		Flux.just( //
+				"a", "aa", "aaa", //
+				"b", "bb", "bbb", //
+				"c", "cc", "ccc", //
+				"d", "dd", "ddd") //
+				.flatMap(fileName -> operations.store(Mono.just(buffer), fileName)) //
+				.blockLast();
+
+		PageRequest pageRequest = PageRequest.of(2, 3, Sort.Direction.ASC, "filename");
+		operations.find(new Query().with(pageRequest)) //
+				.map(GridFSFile::getFilename) //
+				.as(StepVerifier::create) //
+				.expectNext("c", "cc", "ccc") //
+				.verifyComplete();
+	}
+
 	static class Metadata {
 		String version;
 	}