Revise disconnected client error handling in Spring MVC

DisconnectedClientHelper identifies lost connection issues, but it's
not always easy to know if it is the connection to the client or to
another remote host. DisconnectedClientHelper does recognize and
filter out common client exceptions, but there is a possibility for
other similar custom exceptions.

DefaultHandlerExceptionResolver now attempts to set the status to
500, which won't impact a client that has gone away, but it will
set the status correct on the off chance that the exception is
actually a server side issue.

Closes gh-34481

Author: rstoyanchev

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/support/DefaultHandlerExceptionResolver.java

@@ -167,6 +167,13 @@ public class DefaultHandlerExceptionResolver extends AbstractHandlerExceptionRes
 	protected static final Log pageNotFoundLogger = LogFactory.getLog(PAGE_NOT_FOUND_LOG_CATEGORY);
 
 
+	private static final String DISCONNECTED_CLIENT_LOG_CATEGORY =
+			"org.springframework.web.servlet.handler.DisconnectedClient";
+
+	private static final DisconnectedClientHelper disconnectedClientHelper =
+			new DisconnectedClientHelper(DISCONNECTED_CLIENT_LOG_CATEGORY);
+
+
 	/**
 	 * Sets the {@linkplain #setOrder(int) order} to {@link #LOWEST_PRECEDENCE}.
 	 */
@@ -246,7 +253,7 @@ else if (ex instanceof AsyncRequestNotUsableException) {
 				return handleAsyncRequestNotUsableException(
 						(AsyncRequestNotUsableException) ex, request, response, handler);
 			}
-			else if (DisconnectedClientHelper.isClientDisconnectedException(ex)) {
+			else if (disconnectedClientHelper.checkAndLogClientDisconnectedException(ex)) {
 				return handleDisconnectedClientException(ex, request, response, handler);
 			}
 		}
@@ -506,11 +513,11 @@ protected ModelAndView handleAsyncRequestNotUsableException(AsyncRequestNotUsabl
 	}
 
 	/**
-	 * Handle an Exception that indicates the client has gone away. This is
-	 * typically an {@link IOException} of a specific subtype or with a message
-	 * specific to the underlying Servlet container. Those are detected through
-	 * {@link DisconnectedClientHelper#isClientDisconnectedException(Throwable)}
-	 * <p>By default, do nothing since the response is not usable.
+	 * Handle an Exception that indicates the client has gone away as determined
+	 * via {@link DisconnectedClientHelper}.
+	 * <p>By default, as of 7.1 this method attempts to set the response status
+	 * to 500 in case the exception is due to a connection issue to a remote host,
+	 * as part of request handling, rather than to the client.
 	 * @param ex the {@code Exception} to be handled
 	 * @param request current HTTP request
 	 * @param response current HTTP response
@@ -522,6 +529,13 @@ protected ModelAndView handleAsyncRequestNotUsableException(AsyncRequestNotUsabl
 	protected ModelAndView handleDisconnectedClientException(
 			Exception ex, HttpServletRequest request, HttpServletResponse response, @Nullable Object handler) {
 
+		// Attempt to send 500 in case of onward (rather than client) connection issue
+		try {
+			sendServerError(ex, request, response);
+		}
+		catch (Exception ex2) {
+			// ignore
+		}
 		return new ModelAndView();
 	}
 

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/support/DefaultHandlerExceptionResolverTests.java

@@ -16,6 +16,7 @@
 
 package org.springframework.web.servlet.mvc.support;
 
+import java.io.IOException;
 import java.lang.reflect.Method;
 import java.util.Arrays;
 import java.util.Collections;
@@ -269,6 +270,14 @@ protected ModelAndView handleHttpRequestMethodNotSupported(
 		assertThat(actual).isSameAs(expected);
 	}
 
+	@Test // gh-34481
+	void handleDisconnectedClientException() {
+		Exception ex = new IOException("Broken pipe");
+		ModelAndView mav = exceptionResolver.resolveException(request, response, null, ex);
+		assertThat(mav).as("No ModelAndView returned").isNotNull();
+		assertThat(mav.isEmpty()).as("No Empty ModelAndView returned").isTrue();
+		assertThat(response.getStatus()).as("Should attempt to send server error").isEqualTo(500);
+	}
 
 	@SuppressWarnings("unused")
 	public void handle(String arg) {