Remove error logging on ClientAbortException

Update `ErrorPageFilter` so that a Tomcat `ClientAbortException` no
longer causes "Cannot forward to error page for request" logging for
committed responses. Since a `ClientAbortException` indicates that the
client is no longer available it's of no consequence that the request
has been committed and the forward will fail.

Closes gh-13221

Author: philwebb

spring-boot/src/main/java/org/springframework/boot/web/support/ErrorPageFilter.java

@@ -18,8 +18,12 @@
 
 import java.io.IOException;
 import java.io.PrintWriter;
+import java.util.Collection;
+import java.util.Collections;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Map;
+import java.util.Set;
 
 import javax.servlet.Filter;
 import javax.servlet.FilterChain;
@@ -40,6 +44,7 @@
 import org.springframework.boot.web.servlet.ErrorPageRegistry;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
+import org.springframework.util.ClassUtils;
 import org.springframework.web.filter.OncePerRequestFilter;
 import org.springframework.web.util.NestedServletException;
 
@@ -77,6 +82,14 @@ public class ErrorPageFilter implements Filter, ErrorPageRegistry {
 
 	private static final String ERROR_STATUS_CODE = "javax.servlet.error.status_code";
 
+	private static final Set<Class<?>> CLIENT_ABORT_EXCEPTIONS;
+	static {
+		Set<Class<?>> clientAbortExceptions = new HashSet<>();
+		addClassIfPresent(clientAbortExceptions,
+				"org.apache.catalina.connector.ClientAbortException");
+		CLIENT_ABORT_EXCEPTIONS = Collections.unmodifiableSet(clientAbortExceptions);
+	}
+
 	private String global;
 
 	private final Map<Integer, String> statuses = new HashMap<Integer, String>();
@@ -164,7 +177,6 @@ private void handleException(HttpServletRequest request, HttpServletResponse res
 			handleCommittedResponse(request, ex);
 			return;
 		}
-
 		forwardToErrorPage(errorPath, request, wrapped, ex);
 	}
 
@@ -200,6 +212,9 @@ protected String getDescription(HttpServletRequest request) {
 	}
 
 	private void handleCommittedResponse(HttpServletRequest request, Throwable ex) {
+		if (isClientAbortException(ex)) {
+			return;
+		}
 		String message = "Cannot forward to error page for request "
 				+ getDescription(request) + " as the response has already been"
 				+ " committed. As a result, the response may have the wrong status"
@@ -216,6 +231,18 @@ private void handleCommittedResponse(HttpServletRequest request, Throwable ex) {
 		}
 	}
 
+	private boolean isClientAbortException(Throwable ex) {
+		if (ex == null) {
+			return false;
+		}
+		for (Class<?> candidate : CLIENT_ABORT_EXCEPTIONS) {
+			if (candidate.isInstance(ex)) {
+				return true;
+			}
+		}
+		return isClientAbortException(ex.getCause());
+	}
+
 	private String getErrorPath(Map<Integer, String> map, Integer status) {
 		if (map.containsKey(status)) {
 			return map.get(status);
@@ -276,6 +303,15 @@ else if (errorPage.getStatus() != null) {
 	public void destroy() {
 	}
 
+	private static void addClassIfPresent(Collection<Class<?>> collection,
+			String className) {
+		try {
+			collection.add(ClassUtils.forName(className, null));
+		}
+		catch (Throwable ex) {
+		}
+	}
+
 	private static class ErrorWrapperResponse extends HttpServletResponseWrapper {
 
 		private int status;

spring-boot/src/test/java/org/springframework/boot/web/support/ErrorPageFilterTests.java

@@ -28,6 +28,7 @@
 import javax.servlet.http.HttpServletResponse;
 import javax.servlet.http.HttpServletResponseWrapper;
 
+import org.apache.catalina.connector.ClientAbortException;
 import org.junit.Rule;
 import org.junit.Test;
 
@@ -150,6 +151,25 @@ public void doFilter(ServletRequest request, ServletResponse response)
 		assertThat(this.response.isCommitted()).isTrue();
 	}
 
+	@Test
+	public void responseCommittedWhenFromClientAbortException() throws Exception {
+		this.filter.addErrorPages(new ErrorPage("/error"));
+		this.response.setCommitted(true);
+		this.chain = new MockFilterChain() {
+
+			@Override
+			public void doFilter(ServletRequest request, ServletResponse response)
+					throws IOException, ServletException {
+				super.doFilter(request, response);
+				throw new ClientAbortException();
+			}
+
+		};
+		this.filter.doFilter(this.request, this.response, this.chain);
+		assertThat(this.response.isCommitted()).isTrue();
+		assertThat(this.output.toString()).doesNotContain("Cannot forward");
+	}
+
 	@Test
 	public void responseUncommittedWithoutErrorPage() throws Exception {
 		this.chain = new MockFilterChain() {