FilePart and MultipartFile provide transferTo(Path) variant

Also, ZeroCopyHttpOutputMessage provides writeWith(Path, int, int), enforcing that variant as the implementation target in 5.1 (analogous to FilePart).

Issue: SPR-16925

Author: jhoeller

spring-web/src/main/java/org/springframework/http/ZeroCopyHttpOutputMessage.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -17,6 +17,7 @@
 package org.springframework.http;
 
 import java.io.File;
+import java.nio.file.Path;
 
 import reactor.core.publisher.Mono;
 
@@ -25,6 +26,7 @@
  * file transfers.
  *
  * @author Arjen Poutsma
+ * @author Juergen Hoeller
  * @since 5.0
  * @see <a href="https://en.wikipedia.org/wiki/Zero-copy">Zero-copy</a>
  */
@@ -38,6 +40,19 @@ public interface ZeroCopyHttpOutputMessage extends ReactiveHttpOutputMessage {
 	 * @param count the number of bytes to be transferred
 	 * @return a publisher that indicates completion or error.
 	 */
-	Mono<Void> writeWith(File file, long position, long count);
+	default Mono<Void> writeWith(File file, long position, long count) {
+		return writeWith(file.toPath(), position, count);
+	}
+
+	/**
+	 * Use the given {@link Path} to write the body of the message to the underlying
+	 * HTTP layer.
+	 * @param file the file to transfer
+	 * @param position the position within the file from which the transfer is to begin
+	 * @param count the number of bytes to be transferred
+	 * @return a publisher that indicates completion or error.
+	 * @since 5.1
+	 */
+	Mono<Void> writeWith(Path file, long position, long count);
 
 }

spring-web/src/main/java/org/springframework/http/client/reactive/ReactorClientHttpRequest.java

@@ -16,8 +16,8 @@
 
 package org.springframework.http.client.reactive;
 
-import java.io.File;
 import java.net.URI;
+import java.nio.file.Path;
 import java.util.Collection;
 
 import io.netty.buffer.ByteBuf;
@@ -97,8 +97,8 @@ private static Publisher<ByteBuf> toByteBufs(Publisher<? extends DataBuffer> dat
 	}
 
 	@Override
-	public Mono<Void> writeWith(File file, long position, long count) {
-		return doCommit(() -> this.outbound.sendFile(file.toPath(), position, count).then());
+	public Mono<Void> writeWith(Path file, long position, long count) {
+		return doCommit(() -> this.outbound.sendFile(file, position, count).then());
 	}
 
 	@Override

spring-web/src/main/java/org/springframework/http/codec/multipart/FilePart.java

@@ -17,6 +17,7 @@
 package org.springframework.http.codec.multipart;
 
 import java.io.File;
+import java.nio.file.Path;
 
 import reactor.core.publisher.Mono;
 
@@ -25,6 +26,7 @@
  * a multipart request.
  *
  * @author Rossen Stoyanchev
+ * @author Juergen Hoeller
  * @since 5.0
  */
 public interface FilePart extends Part {
@@ -38,10 +40,26 @@ public interface FilePart extends Part {
 	 * Convenience method to copy the content of the file in this part to the
 	 * given destination file. If the destination file already exists, it will
 	 * be truncated first.
+	 * <p>The default implementation delegates to {@link #transferTo(Path)}.
 	 * @param dest the target file
 	 * @return completion {@code Mono} with the result of the file transfer,
 	 * possibly {@link IllegalStateException} if the part isn't a file
+	 * @see #transferTo(Path)
 	 */
-	Mono<Void> transferTo(File dest);
+	default Mono<Void> transferTo(File dest) {
+		return transferTo(dest.toPath());
+	}
+
+	/**
+	 * Convenience method to copy the content of the file in this part to the
+	 * given destination file. If the destination file already exists, it will
+	 * be truncated first.
+	 * @param dest the target file
+	 * @return completion {@code Mono} with the result of the file transfer,
+	 * possibly {@link IllegalStateException} if the part isn't a file
+	 * @since 5.1
+	 * @see #transferTo(File)
+	 */
+	Mono<Void> transferTo(Path dest);
 
 }

spring-web/src/main/java/org/springframework/http/codec/multipart/SynchronossPartHttpMessageReader.java

@@ -16,14 +16,14 @@
 
 package org.springframework.http.codec.multipart;
 
-import java.io.File;
 import java.io.IOException;
 import java.nio.channels.Channels;
 import java.nio.channels.FileChannel;
 import java.nio.channels.ReadableByteChannel;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.OpenOption;
+import java.nio.file.Path;
 import java.nio.file.StandardOpenOption;
 import java.util.Collections;
 import java.util.List;
@@ -90,19 +90,14 @@ public boolean canRead(ResolvableType elementType, @Nullable MediaType mediaType
 
 
 	@Override
-	public Flux<Part> read(ResolvableType elementType, ReactiveHttpInputMessage message,
-			Map<String, Object> hints) {
-
+	public Flux<Part> read(ResolvableType elementType, ReactiveHttpInputMessage message, Map<String, Object> hints) {
 		return Flux.create(new SynchronossPartGenerator(message, this.bufferFactory, this.streamStorageFactory));
 	}
 
 
 	@Override
-	public Mono<Part> readMono(ResolvableType elementType, ReactiveHttpInputMessage message,
-			Map<String, Object> hints) {
-
-		return Mono.error(new UnsupportedOperationException(
-				"Can't read a multipart request body into a single Part."));
+	public Mono<Part> readMono(ResolvableType elementType, ReactiveHttpInputMessage message, Map<String, Object> hints) {
+		return Mono.error(new UnsupportedOperationException("Cannot read multipart request body into single Part"));
 	}
 
 
@@ -118,15 +113,14 @@ private static class SynchronossPartGenerator implements Consumer<FluxSink<Part>
 
 		private final PartBodyStreamStorageFactory streamStorageFactory;
 
-
 		SynchronossPartGenerator(ReactiveHttpInputMessage inputMessage, DataBufferFactory bufferFactory,
 				PartBodyStreamStorageFactory streamStorageFactory) {
+
 			this.inputMessage = inputMessage;
 			this.bufferFactory = bufferFactory;
 			this.streamStorageFactory = streamStorageFactory;
 		}
 
-
 		@Override
 		public void accept(FluxSink<Part> emitter) {
 			HttpHeaders headers = this.inputMessage.getHeaders();
@@ -189,14 +183,12 @@ private static class FluxSinkAdapterListener implements NioMultipartParserListen
 
 		private final AtomicInteger terminated = new AtomicInteger(0);
 
-
 		FluxSinkAdapterListener(FluxSink<Part> sink, DataBufferFactory factory, MultipartContext context) {
 			this.sink = sink;
 			this.bufferFactory = factory;
 			this.context = context;
 		}
 
-
 		@Override
 		public void onPartFinished(StreamStorage storage, Map<String, List<String>> headers) {
 			HttpHeaders httpHeaders = new HttpHeaders();
@@ -250,16 +242,14 @@ private abstract static class AbstractSynchronossPart implements Part {
 
 		private final DataBufferFactory bufferFactory;
 
-
 		AbstractSynchronossPart(HttpHeaders headers, DataBufferFactory bufferFactory) {
 			Assert.notNull(headers, "HttpHeaders is required");
-			Assert.notNull(bufferFactory, "'bufferFactory' is required");
+			Assert.notNull(bufferFactory, "DataBufferFactory is required");
 			this.name = MultipartUtils.getFieldName(headers);
 			this.headers = headers;
 			this.bufferFactory = bufferFactory;
 		}
 
-
 		@Override
 		public String name() {
 			return this.name;
@@ -280,14 +270,12 @@ private static class SynchronossPart extends AbstractSynchronossPart {
 
 		private final StreamStorage storage;
 
-
 		SynchronossPart(HttpHeaders headers, StreamStorage storage, DataBufferFactory factory) {
 			super(headers, factory);
-			Assert.notNull(storage, "'storage' is required");
+			Assert.notNull(storage, "StreamStorage is required");
 			this.storage = storage;
 		}
 
-
 		@Override
 		public Flux<DataBuffer> content() {
 			return DataBufferUtils.readInputStream(getStorage()::getInputStream, getBufferFactory(), 4096);
@@ -301,33 +289,28 @@ protected StreamStorage getStorage() {
 
 	private static class SynchronossFilePart extends SynchronossPart implements FilePart {
 
-		private static final OpenOption[] FILE_CHANNEL_OPTIONS = {
-				StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING, StandardOpenOption.WRITE };
-
+		private static final OpenOption[] FILE_CHANNEL_OPTIONS =
+				{StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING, StandardOpenOption.WRITE};
 
 		private final String filename;
 
-
-		SynchronossFilePart(HttpHeaders headers, String filename, StreamStorage storage,
-				DataBufferFactory factory) {
-
+		SynchronossFilePart(HttpHeaders headers, String filename, StreamStorage storage, DataBufferFactory factory) {
 			super(headers, storage, factory);
 			this.filename = filename;
 		}
 
-
 		@Override
 		public String filename() {
 			return this.filename;
 		}
 
 		@Override
-		public Mono<Void> transferTo(File destination) {
+		public Mono<Void> transferTo(Path dest) {
 			ReadableByteChannel input = null;
 			FileChannel output = null;
 			try {
 				input = Channels.newChannel(getStorage().getInputStream());
-				output = FileChannel.open(destination.toPath(), FILE_CHANNEL_OPTIONS);
+				output = FileChannel.open(dest, FILE_CHANNEL_OPTIONS);
 				long size = (input instanceof FileChannel ? ((FileChannel) input).size() : Long.MAX_VALUE);
 				long totalWritten = 0;
 				while (totalWritten < size) {
@@ -366,13 +349,11 @@ private static class SynchronossFormFieldPart extends AbstractSynchronossPart im
 
 		private final String content;
 
-
 		SynchronossFormFieldPart(HttpHeaders headers, DataBufferFactory bufferFactory, String content) {
 			super(headers, bufferFactory);
 			this.content = content;
 		}
 
-
 		@Override
 		public String value() {
 			return this.content;

spring-web/src/main/java/org/springframework/http/server/reactive/ReactorServerHttpResponse.java

@@ -16,7 +16,7 @@
 
 package org.springframework.http.server.reactive;
 
-import java.io.File;
+import java.nio.file.Path;
 
 import io.netty.buffer.ByteBuf;
 import io.netty.handler.codec.http.HttpResponseStatus;
@@ -112,8 +112,8 @@ protected void applyCookies() {
 	}
 
 	@Override
-	public Mono<Void> writeWith(File file, long position, long count) {
-		return doCommit(() -> this.response.sendFile(file.toPath(), position, count).then());
+	public Mono<Void> writeWith(Path file, long position, long count) {
+		return doCommit(() -> this.response.sendFile(file, position, count).then());
 	}
 
 	private static Publisher<ByteBuf> toByteBufs(Publisher<? extends DataBuffer> dataBuffers) {

spring-web/src/main/java/org/springframework/http/server/reactive/UndertowServerHttpResponse.java

@@ -16,10 +16,10 @@
 
 package org.springframework.http.server.reactive;
 
-import java.io.File;
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.nio.channels.FileChannel;
+import java.nio.file.Path;
 import java.nio.file.StandardOpenOption;
 
 import io.undertow.server.HttpServerExchange;
@@ -106,10 +106,10 @@ protected void applyCookies() {
 	}
 
 	@Override
-	public Mono<Void> writeWith(File file, long position, long count) {
+	public Mono<Void> writeWith(Path file, long position, long count) {
 		return doCommit(() ->
 				Mono.defer(() -> {
-					try (FileChannel source = FileChannel.open(file.toPath(), StandardOpenOption.READ)) {
+					try (FileChannel source = FileChannel.open(file, StandardOpenOption.READ)) {
 						StreamSinkChannel destination = this.exchange.getResponseChannel();
 						Channels.transferBlocking(destination, source, position, count);
 						return Mono.empty();

spring-web/src/main/java/org/springframework/web/multipart/MultipartFile.java

@@ -19,10 +19,13 @@
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
 
 import org.springframework.core.io.InputStreamSource;
 import org.springframework.core.io.Resource;
 import org.springframework.lang.Nullable;
+import org.springframework.util.FileCopyUtils;
 
 /**
  * A representation of an uploaded file received in a multipart request.
@@ -127,4 +130,15 @@ default Resource getResource() {
 	 */
 	void transferTo(File dest) throws IOException, IllegalStateException;
 
+	/**
+	 * Transfer the received file to the given destination file.
+	 * <p>The default implementation simply copies the file input stream.
+	 * @since 5.1
+	 * @see #getInputStream()
+	 * @see #transferTo(File)
+ 	 */
+	default void transferTo(Path dest) throws IOException, IllegalStateException {
+		FileCopyUtils.copy(getInputStream(), Files.newOutputStream(dest));
+	}
+
 }

spring-web/src/main/java/org/springframework/web/multipart/MultipartFileResource.java

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.multipart;
 
 import java.io.IOException;
@@ -35,7 +36,7 @@ class MultipartFileResource extends AbstractResource {
 
 
 	public MultipartFileResource(MultipartFile multipartFile) {
-		Assert.notNull(multipartFile, "MultipartFile must not be null.");
+		Assert.notNull(multipartFile, "MultipartFile must not be null");
 		this.multipartFile = multipartFile;
 	}
 
@@ -86,9 +87,8 @@ public String getDescription() {
 
 	@Override
 	public boolean equals(Object obj) {
-		return (obj == this ||
-				(obj instanceof MultipartFileResource &&
-						((MultipartFileResource) obj).multipartFile.equals(this.multipartFile)));
+		return (obj == this || (obj instanceof MultipartFileResource &&
+				((MultipartFileResource) obj).multipartFile.equals(this.multipartFile)));
 	}
 
 	@Override