DATAMONGO-2393 - Support configurable chunk size.

We now allow consuming GridFS files using a configurable chunk size. The default chunk size is now 256kb.

Original Pull Request: #799

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

@@ -42,12 +42,14 @@ class BinaryStreamAdapters {
 	 *
 	 * @param inputStream must not be {@literal null}.
 	 * @param dataBufferFactory must not be {@literal null}.
+	 * @param bufferSize read {@code n} bytes per iteration.
 	 * @return {@link Flux} emitting {@link DataBuffer}s.
 	 * @see DataBufferFactory#allocateBuffer()
 	 */
-	static Flux<DataBuffer> toPublisher(AsyncInputStream inputStream, DataBufferFactory dataBufferFactory) {
+	static Flux<DataBuffer> toPublisher(AsyncInputStream inputStream, DataBufferFactory dataBufferFactory,
+			int bufferSize) {
 
-		return DataBufferPublisherAdapter.createBinaryStream(inputStream, dataBufferFactory) //
+		return DataBufferPublisherAdapter.createBinaryStream(inputStream, dataBufferFactory, bufferSize) //
 				.filter(it -> {
 
 					if (it.readableByteCount() == 0) {

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

@@ -20,6 +20,7 @@ import reactor.core.publisher.Flux;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
+import java.util.function.IntFunction;
 
 import org.reactivestreams.Publisher;
 
@@ -41,20 +42,19 @@ public class ReactiveGridFsResource extends AbstractResource {
 
 	private final @Nullable GridFSFile file;
 	private final String filename;
-	private final Flux<DataBuffer> content;
+	private final IntFunction<Flux<DataBuffer>> contentFunction;
 
 	/**
 	 * Creates a new, absent {@link ReactiveGridFsResource}.
 	 *
 	 * @param filename filename of the absent resource.
 	 * @param content
-	 * @since 2.1
 	 */
 	private ReactiveGridFsResource(String filename, Publisher<DataBuffer> content) {
 
 		this.file = null;
 		this.filename = filename;
-		this.content = Flux.from(content);
+		this.contentFunction = any -> Flux.from(content);
 	}
 
 	/**
@@ -64,10 +64,21 @@ public class ReactiveGridFsResource extends AbstractResource {
 	 * @param content
 	 */
 	public ReactiveGridFsResource(GridFSFile file, Publisher<DataBuffer> content) {
+		this(file, (IntFunction<Flux<DataBuffer>>) any -> Flux.from(content));
+	}
+
+	/**
+	 * Creates a new {@link ReactiveGridFsResource} from the given {@link GridFSFile}.
+	 *
+	 * @param file must not be {@literal null}.
+	 * @param contentFunction
+	 * @since 2.2.1
+	 */
+	ReactiveGridFsResource(GridFSFile file, IntFunction<Flux<DataBuffer>> contentFunction) {
 
 		this.file = file;
 		this.filename = file.getFilename();
-		this.content = Flux.from(content);
+		this.contentFunction = contentFunction;
 	}
 
 	/**
@@ -165,16 +176,28 @@ public class ReactiveGridFsResource extends AbstractResource {
 	}
 
 	/**
-	 * Retrieve the download stream.
+	 * Retrieve the download stream using the default chunk size of 256kb.
 	 *
 	 * @return
 	 */
 	public Flux<DataBuffer> getDownloadStream() {
+		return getDownloadStream(256 * 1024); // 256kb buffers
+	}
+
+	/**
+	 * Retrieve the download stream.
+	 *
+	 * @param chunkSize chunk size in bytes to use.
+	 * @return
+	 * @since 2.2.1
+	 */
+	public Flux<DataBuffer> getDownloadStream(int chunkSize) {
 
 		if (!exists()) {
 			return Flux.error(new FileNotFoundException(String.format("%s does not exist.", getDescription())));
 		}
-		return this.content;
+
+		return contentFunction.apply(chunkSize);
 	}
 
 	private void verifyExists() throws FileNotFoundException {

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

@@ -223,9 +223,11 @@ public class ReactiveGridFsTemplate extends GridFsOperationsSupport implements R
 
 		return Mono.fromSupplier(() -> {
 
-			GridFSDownloadStream stream = getGridFs().openDownloadStream(file.getId());
+			return new ReactiveGridFsResource(file, chunkSize -> {
 
-			return new ReactiveGridFsResource(file, BinaryStreamAdapters.toPublisher(stream, dataBufferFactory));
+				GridFSDownloadStream stream = getGridFs().openDownloadStream(file.getId());
+				return BinaryStreamAdapters.toPublisher(stream, dataBufferFactory, chunkSize);
+			});
 		});
 	}
 

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

@@ -25,6 +25,7 @@ import java.io.IOException;
 import java.nio.ByteBuffer;
 
 import org.junit.Test;
+
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DataBufferUtils;
@@ -49,7 +50,7 @@ public class BinaryStreamAdaptersUnitTests {
 		byte[] content = StreamUtils.copyToByteArray(resource.getInputStream());
 		AsyncInputStream inputStream = AsyncStreamHelper.toAsyncInputStream(resource.getInputStream());
 
-		Flux<DataBuffer> dataBuffers = BinaryStreamAdapters.toPublisher(inputStream, new DefaultDataBufferFactory());
+		Flux<DataBuffer> dataBuffers = BinaryStreamAdapters.toPublisher(inputStream, new DefaultDataBufferFactory(), 256);
 
 		DataBufferUtils.join(dataBuffers) //
 				.as(StepVerifier::create) //

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

@@ -44,7 +44,7 @@ public class DataBufferPublisherAdapterUnitTests {
 		when(asyncInput.read(any())).thenReturn(Mono.just(1), Mono.error(new IllegalStateException()));
 		when(asyncInput.close()).thenReturn(Mono.empty());
 
-		Flux<DataBuffer> binaryStream = DataBufferPublisherAdapter.createBinaryStream(asyncInput, factory);
+		Flux<DataBuffer> binaryStream = DataBufferPublisherAdapter.createBinaryStream(asyncInput, factory, 256);
 
 		StepVerifier.create(binaryStream, 0) //
 				.thenRequest(1) //

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

@@ -24,6 +24,7 @@ import reactor.core.publisher.Flux;
 import reactor.test.StepVerifier;
 
 import java.io.IOException;
+import java.nio.ByteBuffer;
 import java.util.UUID;
 
 import org.bson.BsonObjectId;
@@ -40,7 +41,9 @@ 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.mongodb.ReactiveMongoDatabaseFactory;
 import org.springframework.data.mongodb.core.SimpleMongoDbFactory;
+import org.springframework.data.mongodb.core.convert.MongoConverter;
 import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.test.context.ContextConfiguration;
 import org.springframework.test.context.junit4.SpringRunner;
@@ -48,6 +51,7 @@ import org.springframework.util.StreamUtils;
 
 import com.mongodb.gridfs.GridFS;
 import com.mongodb.gridfs.GridFSInputFile;
+import com.mongodb.internal.HexUtils;
 import com.mongodb.reactivestreams.client.gridfs.AsyncInputStream;
 import com.mongodb.reactivestreams.client.gridfs.helpers.AsyncStreamHelper;
 
@@ -66,6 +70,8 @@ public class ReactiveGridFsTemplateTests {
 
 	@Autowired ReactiveGridFsOperations operations;
 	@Autowired SimpleMongoDbFactory mongoClient;
+	@Autowired ReactiveMongoDatabaseFactory dbFactory;
+	@Autowired MongoConverter mongoConverter;
 
 	@Before
 	public void setUp() {
@@ -92,6 +98,48 @@ public class ReactiveGridFsTemplateTests {
 				.verifyComplete();
 	}
 
+	@Test // DATAMONGO-1855
+	public void storesAndLoadsLargeFileCorrectly() {
+
+		ByteBuffer buffer = ByteBuffer.allocate(1000 * 1000 * 1); // 1 mb
+
+		int i = 0;
+		while (buffer.remaining() != 0) {
+			byte b = (byte) (i++ % 16);
+			String string = HexUtils.toHex(new byte[] { b });
+			buffer.put(string.getBytes());
+		}
+		buffer.flip();
+
+		DefaultDataBufferFactory factory = new DefaultDataBufferFactory();
+
+		ObjectId reference = operations.store(Flux.just(factory.wrap(buffer)), "large.txt").block();
+
+		buffer.clear();
+
+		// default chunk size
+		operations.findOne(query(where("_id").is(reference))).flatMap(operations::getResource)
+				.flatMapMany(ReactiveGridFsResource::getDownloadStream) //
+				.transform(DataBufferUtils::join) //
+				.as(StepVerifier::create) //
+				.consumeNextWith(dataBuffer -> {
+
+					assertThat(dataBuffer.readableByteCount()).isEqualTo(buffer.remaining());
+					assertThat(dataBuffer.asByteBuffer()).isEqualTo(buffer);
+				}).verifyComplete();
+
+		// small chunk size
+		operations.findOne(query(where("_id").is(reference))).flatMap(operations::getResource)
+				.flatMapMany(reactiveGridFsResource -> reactiveGridFsResource.getDownloadStream(256)) //
+				.transform(DataBufferUtils::join) //
+				.as(StepVerifier::create) //
+				.consumeNextWith(dataBuffer -> {
+
+					assertThat(dataBuffer.readableByteCount()).isEqualTo(buffer.remaining());
+					assertThat(dataBuffer.asByteBuffer()).isEqualTo(buffer);
+				}).verifyComplete();
+	}
+
 	@Test // DATAMONGO-2392
 	public void storesAndFindsByUUID() throws IOException {