Disable ShallowEtagHeaderFilter for HTTP streaming

Issue: SPR-12960

spring-web/src/main/java/org/springframework/web/filter/ShallowEtagHeaderFilter.java

@@ -18,8 +18,12 @@ package org.springframework.web.filter;
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.io.PrintWriter;
+
 import javax.servlet.FilterChain;
 import javax.servlet.ServletException;
+import javax.servlet.ServletOutputStream;
+import javax.servlet.ServletRequest;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
@@ -55,11 +59,12 @@ public class ShallowEtagHeaderFilter extends OncePerRequestFilter {
 
 	private static final String DIRECTIVE_NO_STORE = "no-store";
 
-
 	/** Checking for Servlet 3.0+ HttpServletResponse.getHeader(String) */
 	private static final boolean responseGetHeaderAvailable =
 			ClassUtils.hasMethod(HttpServletResponse.class, "getHeader", String.class);
 
+	private static final String STREAMING_ATTRIBUTE = ShallowEtagHeaderFilter.class.getName() + ".STREAMING";
+
 
 	/**
 	 * The default value is "false" so that the filter may delay the generation of
@@ -76,12 +81,12 @@ public class ShallowEtagHeaderFilter extends OncePerRequestFilter {
 
 		HttpServletResponse responseToUse = response;
 		if (!isAsyncDispatch(request) && !(response instanceof ContentCachingResponseWrapper)) {
-			responseToUse = new ContentCachingResponseWrapper(response);
+			responseToUse = new HttpStreamingAwareContentCachingResponseWrapper(response, request);
 		}
 
 		filterChain.doFilter(request, responseToUse);
 
-		if (!isAsyncStarted(request)) {
+		if (!isAsyncStarted(request) && !isContentCachingDisabled(request)) {
 			updateResponse(request, responseToUse);
 		}
 	}
@@ -90,7 +95,6 @@ public class ShallowEtagHeaderFilter extends OncePerRequestFilter {
 		ContentCachingResponseWrapper responseWrapper =
 				WebUtils.getNativeResponse(response, ContentCachingResponseWrapper.class);
 		Assert.notNull(responseWrapper, "ShallowEtagResponseWrapper not found");
-
 		HttpServletResponse rawResponse = (HttpServletResponse) responseWrapper.getResponse();
 		int statusCode = responseWrapper.getStatusCode();
 
@@ -169,4 +173,48 @@ public class ShallowEtagHeaderFilter extends OncePerRequestFilter {
 		return builder.toString();
 	}
 
+	/**
+	 * This method can be used to disable the content caching response wrapper
+	 * of the ShallowEtagHeaderFilter. This can be done before the start of HTTP
+	 * streaming for example where the response will be written to asynchronously
+	 * and not in the context of a Servlet container thread.
+	 * @since 4.2
+	 */
+	public static void disableContentCaching(ServletRequest request) {
+		Assert.notNull(request);
+		request.setAttribute(STREAMING_ATTRIBUTE, true);
+	}
+
+	private static boolean isContentCachingDisabled(HttpServletRequest request) {
+		return (request.getAttribute(STREAMING_ATTRIBUTE) != null);
+	}
+
+
+	private static class HttpStreamingAwareContentCachingResponseWrapper extends ContentCachingResponseWrapper {
+
+		private final HttpServletRequest request;
+
+
+		public HttpStreamingAwareContentCachingResponseWrapper(HttpServletResponse response,
+				HttpServletRequest request) {
+
+			super(response);
+			this.request = request;
+		}
+
+		@Override
+		public ServletOutputStream getOutputStream() throws IOException {
+			return (useRawResponse() ? getResponse().getOutputStream() : super.getOutputStream());
+		}
+
+		@Override
+		public PrintWriter getWriter() throws IOException {
+			return (useRawResponse() ? getResponse().getWriter() : super.getWriter());
+		}
+
+		private boolean useRawResponse() {
+			return isContentCachingDisabled(this.request);
+		}
+	}
+
 }

spring-web/src/main/java/org/springframework/web/util/ContentCachingResponseWrapper.java

@@ -91,7 +91,7 @@ public class ContentCachingResponseWrapper extends HttpServletResponseWrapper {
 	}
 
 	@Override
-	public ServletOutputStream getOutputStream() {
+	public ServletOutputStream getOutputStream() throws IOException {
 		return this.outputStream;
 	}