Add writeAndFlushWith to ReactiveHttpOutputMessage

This commit changes the reactive flushing mechanism to use a newly
introduced writeAndFlushWith(Publisher<Publisher<DataBuffer>>) on
ReactiveHttpOutputMessage instead of using the FlushingDataBuffer.

Issue: https://github.com/spring-projects/spring-reactive/issues/125

spring-core/src/main/java/org/springframework/core/io/buffer/FlushingDataBuffer.java

@@ -1,125 +0,0 @@
-/*
- * Copyright 2002-2016 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
- *
- *      http://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.core.io.buffer;
-
-import java.io.InputStream;
-import java.io.OutputStream;
-import java.nio.ByteBuffer;
-import java.util.function.IntPredicate;
-
-/**
- * Empty {@link DataBuffer} that indicates to the file or the socket writing it
- * that previously buffered data should be flushed.
- *
- * @author Sebastien Deleuze
- * @since 5.0
- * @see FlushingDataBuffer#INSTANCE
- */
-public class FlushingDataBuffer implements DataBuffer {
-
-	/** Singleton instance of this class */
-	public static final FlushingDataBuffer INSTANCE = new FlushingDataBuffer();
-
-	private final DataBuffer buffer;
-
-
-	private FlushingDataBuffer() {
-		this.buffer = new DefaultDataBufferFactory().allocateBuffer(0);
-	}
-
-
-	@Override
-	public DataBufferFactory factory() {
-		return this.buffer.factory();
-	}
-
-	@Override
-	public int indexOf(IntPredicate predicate, int fromIndex) {
-		return this.buffer.indexOf(predicate, fromIndex);
-	}
-
-	@Override
-	public int lastIndexOf(IntPredicate predicate, int fromIndex) {
-		return this.buffer.lastIndexOf(predicate, fromIndex);
-	}
-
-	@Override
-	public int readableByteCount() {
-		return this.buffer.readableByteCount();
-	}
-
-	@Override
-	public byte read() {
-		return this.buffer.read();
-	}
-
-	@Override
-	public DataBuffer read(byte[] destination) {
-		return this.buffer.read(destination);
-	}
-
-	@Override
-	public DataBuffer read(byte[] destination, int offset, int length) {
-		return this.buffer.read(destination, offset, length);
-	}
-
-	@Override
-	public DataBuffer write(byte b) {
-		return this.buffer.write(b);
-	}
-
-	@Override
-	public DataBuffer write(byte[] source) {
-		return this.buffer.write(source);
-	}
-
-	@Override
-	public DataBuffer write(byte[] source, int offset, int length) {
-		return this.buffer.write(source, offset, length);
-	}
-
-	@Override
-	public DataBuffer write(DataBuffer... buffers) {
-		return this.buffer.write(buffers);
-	}
-
-	@Override
-	public DataBuffer write(ByteBuffer... buffers) {
-		return this.buffer.write(buffers);
-	}
-
-	@Override
-	public DataBuffer slice(int index, int length) {
-		return this.buffer.slice(index, length);
-	}
-
-	@Override
-	public ByteBuffer asByteBuffer() {
-		return this.buffer.asByteBuffer();
-	}
-
-	@Override
-	public InputStream asInputStream() {
-		return this.buffer.asInputStream();
-	}
-
-	@Override
-	public OutputStream asOutputStream() {
-		return this.buffer.asOutputStream();
-	}
-
-}

spring-core/src/main/java/org/springframework/core/io/buffer/NettyDataBufferFactory.java

@@ -78,6 +78,24 @@ public class NettyDataBufferFactory implements DataBufferFactory {
 		return new NettyDataBuffer(byteBuf, this);
 	}
 
+	/**
+	 * Returns the given Netty {@link DataBuffer} as a {@link ByteBuf}. Returns the
+	 * {@linkplain NettyDataBuffer#getNativeBuffer() native buffer} if {@code buffer} is
+	 * a {@link NettyDataBuffer}; returns {@link Unpooled#wrappedBuffer(ByteBuffer)}
+	 * otherwise.
+	 * @param buffer the {@code DataBuffer} to return a {@code ByteBuf} for.
+	 * @return the netty {@code ByteBuf}
+	 */
+	public static ByteBuf toByteBuf(DataBuffer buffer) {
+		if (buffer instanceof NettyDataBuffer) {
+			return ((NettyDataBuffer) buffer).getNativeBuffer();
+		}
+		else {
+			return Unpooled.wrappedBuffer(buffer.asByteBuffer());
+		}
+	}
+
+
 	@Override
 	public String toString() {
 		return "NettyDataBufferFactory (" + this.byteBufAllocator + ")";