Use ByteBuffer support in ServletHttpHandlerAdapter

As of Servlet 6.1, the `ServletInputStream` and `ServletOutputStream`
offer read and write variants based on `ByteBuffer` instead of byte
arrays. This can improve performance and avoid memory copy for I/O
calls.

This was already partially supported for some servers like Tomcat
through specific adapters. This commit moves this support to the
standard `ServletHttpHandlerAdapter` and makes it available for all
Servlet 6.1+ containers.

Closes gh-33748

Author: bclozel

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

@@ -20,6 +20,7 @@
 import java.net.InetSocketAddress;
 import java.net.URI;
 import java.net.URISyntaxException;
+import java.nio.ByteBuffer;
 import java.nio.charset.Charset;
 import java.security.cert.X509Certificate;
 import java.util.Enumeration;
@@ -38,6 +39,7 @@
 
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DataBufferFactory;
+import org.springframework.core.io.buffer.DataBufferUtils;
 import org.springframework.core.io.buffer.DefaultDataBufferFactory;
 import org.springframework.http.HttpCookie;
 import org.springframework.http.HttpHeaders;
@@ -58,6 +60,7 @@
  *
  * @author Rossen Stoyanchev
  * @author Juergen Hoeller
+ * @author Brian Clozel
  * @since 5.0
  */
 class ServletServerHttpRequest extends AbstractServerHttpRequest {
@@ -75,7 +78,7 @@ class ServletServerHttpRequest extends AbstractServerHttpRequest {
 
 	private final DataBufferFactory bufferFactory;
 
-	private final byte[] buffer;
+	private final int bufferSize;
 
 	private final AsyncListener asyncListener;
 
@@ -99,7 +102,7 @@ public ServletServerHttpRequest(MultiValueMap<String, String> headers, HttpServl
 
 		this.request = request;
 		this.bufferFactory = bufferFactory;
-		this.buffer = new byte[bufferSize];
+		this.bufferSize = bufferSize;
 
 		this.asyncListener = new RequestAsyncListener();
 
@@ -275,20 +278,31 @@ protected final ServletInputStream getInputStream() {
 	 * or {@link #EOF_BUFFER} if the input stream returned -1.
 	 */
 	DataBuffer readFromInputStream() throws IOException {
-		int read = this.inputStream.read(this.buffer);
-		logBytesRead(read);
-
-		if (read > 0) {
-			DataBuffer dataBuffer = this.bufferFactory.allocateBuffer(read);
-			dataBuffer.write(this.buffer, 0, read);
-			return dataBuffer;
+		DataBuffer dataBuffer = this.bufferFactory.allocateBuffer(this.bufferSize);
+		int read = -1;
+		try {
+			try (DataBuffer.ByteBufferIterator iterator = dataBuffer.writableByteBuffers()) {
+				Assert.state(iterator.hasNext(), "No ByteBuffer available");
+				ByteBuffer byteBuffer = iterator.next();
+				read = this.inputStream.read(byteBuffer);
+			}
+			logBytesRead(read);
+			if (read > 0) {
+				dataBuffer.writePosition(read);
+				return dataBuffer;
+			}
+			else if (read == -1) {
+				return EOF_BUFFER;
+			}
+			else {
+				return AbstractListenerReadPublisher.EMPTY_BUFFER;
+			}
 		}
-
-		if (read == -1) {
-			return EOF_BUFFER;
+		finally {
+			if (read <= 0) {
+				DataBufferUtils.release(dataBuffer);
+			}
 		}
-
-		return AbstractListenerReadPublisher.EMPTY_BUFFER;
 	}
 
 	protected final void logBytesRead(int read) {

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

@@ -17,7 +17,7 @@
 package org.springframework.http.server.reactive;
 
 import java.io.IOException;
-import java.io.InputStream;
+import java.nio.ByteBuffer;
 import java.nio.charset.Charset;
 
 import jakarta.servlet.AsyncContext;
@@ -45,6 +45,7 @@
  *
  * @author Rossen Stoyanchev
  * @author Juergen Hoeller
+ * @author Brian Clozel
  * @since 5.0
  */
 class ServletServerHttpResponse extends AbstractListenerServerHttpResponse {
@@ -222,15 +223,15 @@ protected final ServletOutputStream getOutputStream() {
 	 */
 	protected int writeToOutputStream(DataBuffer dataBuffer) throws IOException {
 		ServletOutputStream outputStream = this.outputStream;
-		InputStream input = dataBuffer.asInputStream();
-		int bytesWritten = 0;
-		byte[] buffer = new byte[this.bufferSize];
-		int bytesRead;
-		while (outputStream.isReady() && (bytesRead = input.read(buffer)) != -1) {
-			outputStream.write(buffer, 0, bytesRead);
-			bytesWritten += bytesRead;
+		int len = 0;
+		try (DataBuffer.ByteBufferIterator iterator = dataBuffer.readableByteBuffers()) {
+			while (iterator.hasNext() && outputStream.isReady()) {
+				ByteBuffer byteBuffer = iterator.next();
+				len += byteBuffer.remaining();
+				outputStream.write(byteBuffer);
+			}
 		}
-		return bytesWritten;
+		return len;
 	}
 
 	private void flush() throws IOException {

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -26,16 +26,12 @@
 import jakarta.servlet.http.HttpServletRequestWrapper;
 import jakarta.servlet.http.HttpServletResponse;
 import jakarta.servlet.http.HttpServletResponseWrapper;
-import org.apache.catalina.connector.CoyoteInputStream;
-import org.apache.catalina.connector.CoyoteOutputStream;
 import org.apache.catalina.connector.RequestFacade;
 import org.apache.catalina.connector.ResponseFacade;
 import org.apache.coyote.Request;
 import org.apache.coyote.Response;
 
-import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DataBufferFactory;
-import org.springframework.core.io.buffer.DataBufferUtils;
 import org.springframework.http.HttpHeaders;
 import org.springframework.util.Assert;
 import org.springframework.util.MultiValueMap;
@@ -81,10 +77,6 @@ private static final class TomcatServerHttpRequest extends ServletServerHttpRequ
 
 		private static final Field COYOTE_REQUEST_FIELD;
 
-		private final int bufferSize;
-
-		private final DataBufferFactory factory;
-
 		static {
 			Field field = ReflectionUtils.findField(RequestFacade.class, "request");
 			Assert.state(field != null, "Incompatible Tomcat implementation");
@@ -97,8 +89,6 @@ private static final class TomcatServerHttpRequest extends ServletServerHttpRequ
 				throws IOException, URISyntaxException {
 
 			super(createTomcatHttpHeaders(request), request, context, servletPath, factory, bufferSize);
-			this.factory = factory;
-			this.bufferSize = bufferSize;
 		}
 
 		private static MultiValueMap<String, String> createTomcatHttpHeaders(HttpServletRequest request) {
@@ -124,41 +114,6 @@ else if (request instanceof HttpServletRequestWrapper wrapper) {
 			}
 		}
 
-		@Override
-		protected DataBuffer readFromInputStream() throws IOException {
-			if (getInputStream() instanceof CoyoteInputStream coyoteInputStream) {
-				DataBuffer dataBuffer = this.factory.allocateBuffer(this.bufferSize);
-				int read = -1;
-				try {
-					try (DataBuffer.ByteBufferIterator iterator = dataBuffer.writableByteBuffers()) {
-						Assert.state(iterator.hasNext(), "No ByteBuffer available");
-						ByteBuffer byteBuffer = iterator.next();
-						read = coyoteInputStream.read(byteBuffer);
-					}
-					logBytesRead(read);
-					if (read > 0) {
-						dataBuffer.writePosition(read);
-						return dataBuffer;
-					}
-					else if (read == -1) {
-						return EOF_BUFFER;
-					}
-					else {
-						return AbstractListenerReadPublisher.EMPTY_BUFFER;
-					}
-				}
-				finally {
-					if (read <= 0) {
-						DataBufferUtils.release(dataBuffer);
-					}
-				}
-			}
-			else {
-				// It's possible InputStream can be wrapped, preventing use of CoyoteInputStream
-				return super.readFromInputStream();
-			}
-
-		}
 	}
 
 
@@ -208,23 +163,6 @@ protected void applyHeaders() {
 			adaptHeaders(true);
 		}
 
-		@Override
-		protected int writeToOutputStream(DataBuffer dataBuffer) throws IOException {
-			if (getOutputStream() instanceof CoyoteOutputStream coyoteOutputStream) {
-				int len = 0;
-				try (DataBuffer.ByteBufferIterator iterator = dataBuffer.readableByteBuffers()) {
-					while (iterator.hasNext() && coyoteOutputStream.isReady()) {
-						ByteBuffer byteBuffer = iterator.next();
-						len += byteBuffer.remaining();
-						coyoteOutputStream.write(byteBuffer);
-					}
-				}
-				return len;
-			}
-			else {
-				return super.writeToOutputStream(dataBuffer);
-			}
-		}
 	}
 
 }

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

@@ -22,7 +22,6 @@
 import org.eclipse.jetty.server.Server;
 import org.eclipse.jetty.server.ServerConnector;
 
-import org.springframework.http.server.reactive.JettyHttpHandlerAdapter;
 import org.springframework.http.server.reactive.ServletHttpHandlerAdapter;
 
 /**
@@ -41,7 +40,7 @@ protected void initServer() throws Exception {
 
 		this.jettyServer = new Server();
 
-		ServletHttpHandlerAdapter servlet = createServletAdapter();
+		ServletHttpHandlerAdapter servlet = new ServletHttpHandlerAdapter(resolveHttpHandler());
 		ServletHolder servletHolder = new ServletHolder(servlet);
 		servletHolder.setAsyncSupported(true);
 
@@ -56,10 +55,6 @@ protected void initServer() throws Exception {
 		this.jettyServer.setHandler(this.contextHandler);
 	}
 
-	private ServletHttpHandlerAdapter createServletAdapter() {
-		return new JettyHttpHandlerAdapter(resolveHttpHandler());
-	}
-
 	@Override
 	protected void startInternal() throws Exception {
 		this.jettyServer.start();