Refactor FluxWriter to use more straight through processing

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/reactive/result/view/FluxWriter.java

@@ -19,6 +19,8 @@
 import java.io.IOException;
 import java.io.Writer;
 import java.nio.charset.Charset;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.function.Supplier;
 
 import org.reactivestreams.Publisher;
@@ -39,7 +41,9 @@ class FluxWriter extends Writer {
 
 	private final Charset charset;
 
-	private Flux<String> buffers;
+	private List<String> current = new ArrayList<>();
+
+	private List<Object> accumulated = new ArrayList<>();
 
 	public FluxWriter(Supplier<DataBuffer> factory) {
 		this(factory, Charset.defaultCharset());
@@ -48,17 +52,32 @@ public FluxWriter(Supplier<DataBuffer> factory) {
 	public FluxWriter(Supplier<DataBuffer> factory, Charset charset) {
 		this.factory = factory;
 		this.charset = charset;
-		this.buffers = Flux.empty();
 	}
 
 	public Publisher<? extends Publisher<? extends DataBuffer>> getBuffers() {
-		return this.buffers
-				.map(string -> Mono.just(buffer().write(string, this.charset)));
+		Flux<String> buffers = Flux.empty();
+		if (!this.current.isEmpty()) {
+			this.accumulated.add(new ArrayList<>(this.current));
+			this.current.clear();
+		}
+		for (Object thing : this.accumulated) {
+			if (thing instanceof Publisher) {
+				@SuppressWarnings("unchecked")
+				Publisher<String> publisher = (Publisher<String>) thing;
+				buffers = buffers.concatWith(publisher);
+			}
+			else {
+				@SuppressWarnings("unchecked")
+				List<String> list = (List<String>) thing;
+				buffers = buffers.concatWithValues(list.toArray(new String[0]));
+			}
+		}
+		return buffers.map(string -> Mono.just(buffer().write(string, this.charset)));
 	}
 
 	@Override
 	public void write(char[] cbuf, int off, int len) throws IOException {
-		this.buffers = this.buffers.concatWith(Mono.just(new String(cbuf, off, len)));
+		this.current.add(new String(cbuf, off, len));
 	}
 
 	@Override
@@ -79,13 +98,15 @@ private DataBuffer buffer() {
 
 	public void write(Object thing) {
 		if (thing instanceof Publisher) {
-			@SuppressWarnings("unchecked")
-			Publisher<String> publisher = (Publisher<String>) thing;
-			this.buffers = this.buffers.concatWith(Flux.from(publisher));
+			if (!this.current.isEmpty()) {
+				this.accumulated.add(new ArrayList<>(this.current));
+				this.current.clear();
+			}
+			this.accumulated.add(thing);
 		}
 		else {
 			if (thing instanceof String) {
-				this.buffers = this.buffers.concatWith(Mono.just((String) thing));
+				this.current.add((String) thing);
 			}
 		}
 	}