Turn FlushingDataBuffer to an empty DataBuffer

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

@@ -21,26 +21,25 @@ import java.io.OutputStream;
 import java.nio.ByteBuffer;
 import java.util.function.IntPredicate;
 
-import org.springframework.util.Assert;
-
 /**
- * {@link DataBuffer} wrapper that indicates the file or the socket writing this buffer
- * should be flushed.
+ * Empty {@link DataBuffer} that indicates to the file or the socket writing it that
+ * previously buffered data should be flushed.
  *
  * @author Sebastien Deleuze
+ * @see FlushingDataBuffer#INSTANCE
  */
 public class FlushingDataBuffer implements DataBuffer {
 
+	/** Singleton instance of this class */
+	public static final FlushingDataBuffer INSTANCE = new FlushingDataBuffer();
+
 	private final DataBuffer buffer;
 
-	public FlushingDataBuffer() {
+
+	private FlushingDataBuffer() {
 		this.buffer = new DefaultDataBufferFactory().allocateBuffer(0);
 	}
 
-	public FlushingDataBuffer(DataBuffer buffer) {
-		Assert.notNull(buffer);
-		this.buffer = buffer;
-	}
 
 	@Override
 	public DataBufferFactory factory() {

spring-web-reactive/src/main/java/org/springframework/http/codec/SseEventEncoder.java

@@ -115,7 +115,8 @@ public class SseEventEncoder extends AbstractEncoder<Object> {
 			return Flux.concat(
 					encodeString(sb.toString(), bufferFactory),
 					dataBuffer,
-					encodeString("\n", bufferFactory).map(b -> new FlushingDataBuffer(b))
+					encodeString("\n", bufferFactory),
+					Mono.just(FlushingDataBuffer.INSTANCE)
 			);
 		});
 

spring-web-reactive/src/test/java/org/springframework/core/codec/support/SseEventEncoderTests.java

@@ -18,6 +18,7 @@ package org.springframework.core.codec.support;
 
 import java.util.Arrays;
 
+import static org.junit.Assert.*;
 import org.junit.Test;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
@@ -26,14 +27,11 @@ import reactor.core.test.TestSubscriber;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.io.buffer.AbstractDataBufferAllocatingTestCase;
 import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.core.io.buffer.FlushingDataBuffer;
 import org.springframework.http.codec.SseEventEncoder;
 import org.springframework.util.MimeType;
 import org.springframework.web.reactive.sse.SseEvent;
 
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
-
-
 /**
  * @author Sebastien Deleuze
  */
@@ -77,7 +75,8 @@ public class SseEventEncoderTests extends AbstractDataBufferAllocatingTestCase {
 								"event:foo\n" +
 								"retry:123\n" +
 								":bla\n:bla bla\n:bla bla bla\n"),
-						stringConsumer("\n")
+						stringConsumer("\n"),
+						b -> assertEquals(FlushingDataBuffer.class, b.getClass())
 				);
 	}
 
@@ -93,8 +92,10 @@ public class SseEventEncoderTests extends AbstractDataBufferAllocatingTestCase {
 				.assertValuesWith(
 						stringConsumer("data:foo\n"),
 						stringConsumer("\n"),
+						b -> assertEquals(FlushingDataBuffer.class, b.getClass()),
 						stringConsumer("data:bar\n"),
-						stringConsumer("\n")
+						stringConsumer("\n"),
+						b -> assertEquals(FlushingDataBuffer.class, b.getClass())
 				);
 	}
 
@@ -110,12 +111,13 @@ public class SseEventEncoderTests extends AbstractDataBufferAllocatingTestCase {
 				.assertValuesWith(
 						stringConsumer("data:foo\ndata:bar\n"),
 						stringConsumer("\n"),
+						b -> assertEquals(FlushingDataBuffer.class, b.getClass()),
 						stringConsumer("data:foo\ndata:baz\n"),
-						stringConsumer("\n")
+						stringConsumer("\n"),
+						b -> assertEquals(FlushingDataBuffer.class, b.getClass())
 				);
 	}
 
-
 	@Test
 	public void encodePojo() {
 		SseEventEncoder encoder = new SseEventEncoder(Arrays.asList(new JacksonJsonEncoder()));
@@ -130,10 +132,12 @@ public class SseEventEncoderTests extends AbstractDataBufferAllocatingTestCase {
 						stringConsumer("{\"foo\":\"foofoo\",\"bar\":\"barbar\"}"),
 						stringConsumer("\n"),
 						stringConsumer("\n"),
+						b -> assertEquals(FlushingDataBuffer.class, b.getClass()),
 						stringConsumer("data:"),
 						stringConsumer("{\"foo\":\"foofoofoo\",\"bar\":\"barbarbar\"}"),
 						stringConsumer("\n"),
-						stringConsumer("\n")
+						stringConsumer("\n"),
+						b -> assertEquals(FlushingDataBuffer.class, b.getClass())
 				);
 	}
 

spring-web-reactive/src/test/java/org/springframework/http/server/reactive/FlushingIntegrationTests.java

@@ -70,14 +70,15 @@ public class FlushingIntegrationTests extends AbstractHttpHandlerIntegrationTest
 		public Mono<Void> handle(ServerHttpRequest request, ServerHttpResponse response) {
 			Flux<DataBuffer> responseBody = Flux
 					.interval(50)
-					.take(2)
-					.concatWith(Flux.never())
 					.map(l -> {
 						byte[] data = ("data" + l).getBytes();
 						DataBuffer buffer = response.bufferFactory().allocateBuffer(data.length);
 						buffer.write(data);
-						return new FlushingDataBuffer(buffer);
-					});
+						return buffer;
+					})
+					.take(2)
+					.concatWith(Mono.just(FlushingDataBuffer.INSTANCE))
+					.concatWith(Flux.never());
 			return response.writeWith(responseBody);
 		}
 	}