Improve exception logging in HandlerExceptionResolvers

This commit updates AbstractHandlerExceptionResolver to only log at the
WARN level exceptions that are actually resolved by the
ExceptionResolver.

In case developers wish to log each time an ExceptionResolver is called,
a DEBUG level log is still available.

Issue: SPR-14392

spring-webmvc/src/main/java/org/springframework/web/servlet/handler/AbstractHandlerExceptionResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -17,6 +17,7 @@
 package org.springframework.web.servlet.handler;
 
 import java.util.Set;
+
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
@@ -128,13 +129,15 @@ public abstract class AbstractHandlerExceptionResolver implements HandlerExcepti
 			Object handler, Exception ex) {
 
 		if (shouldApplyTo(request, handler)) {
-			// Log exception, both at debug log level and at warn level, if desired.
 			if (this.logger.isDebugEnabled()) {
 				this.logger.debug("Resolving exception from handler [" + handler + "]: " + ex);
 			}
-			logException(ex, request);
 			prepareResponse(ex, response);
-			return doResolveException(request, response, handler, ex);
+			ModelAndView result = doResolveException(request, response, handler, ex);
+			if (result != null) {
+				logException(ex, request);
+			}
+			return result;
 		}
 		else {
 			return null;
@@ -194,7 +197,7 @@ public abstract class AbstractHandlerExceptionResolver implements HandlerExcepti
 	 * @return the log message to use
 	 */
 	protected String buildLogMessage(Exception ex, HttpServletRequest request) {
-		return "Handler execution resulted in exception: " + ex;
+		return "Resolved exception caused by Handler execution: " + ex;
 	}
 
 	/**

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/annotation/ResponseStatusExceptionResolverTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -20,6 +20,7 @@ import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.util.Locale;
 
+import org.junit.Before;
 import org.junit.Test;
 
 import org.springframework.beans.TypeMismatchException;
@@ -49,6 +50,11 @@ public class ResponseStatusExceptionResolverTests {
 
 	private final MockHttpServletResponse response = new MockHttpServletResponse();
 
+	@Before
+	public void setup() {
+		exceptionResolver.setWarnLogCategory(exceptionResolver.getClass().getName());
+	}
+
 	@Test
 	public void statusCode() {
 		StatusCodeException ex = new StatusCodeException();

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/ExceptionHandlerExceptionResolverTests.java

@@ -80,6 +80,7 @@ public class ExceptionHandlerExceptionResolverTests {
 	@Before
 	public void setup() throws Exception {
 		this.resolver = new ExceptionHandlerExceptionResolver();
+		this.resolver.setWarnLogCategory(this.resolver.getClass().getName());
 		this.request = new MockHttpServletRequest("GET", "/");
 		this.response = new MockHttpServletResponse();
 	}
@@ -399,11 +400,13 @@ public class ExceptionHandlerExceptionResolverTests {
 	@Configuration
 	static class MyConfig {
 
-		@Bean public TestExceptionResolver testExceptionResolver() {
+		@Bean
+		public TestExceptionResolver testExceptionResolver() {
 			return new TestExceptionResolver();
 		}
 
-		@Bean public AnotherTestExceptionResolver anotherTestExceptionResolver() {
+		@Bean
+		public AnotherTestExceptionResolver anotherTestExceptionResolver() {
 			return new AnotherTestExceptionResolver();
 		}
 	}
@@ -445,15 +448,18 @@ public class ExceptionHandlerExceptionResolverTests {
 	@Configuration
 	static class MyControllerAdviceConfig {
 
-		@Bean public NotCalledTestExceptionResolver notCalledTestExceptionResolver() {
+		@Bean
+		public NotCalledTestExceptionResolver notCalledTestExceptionResolver() {
 			return new NotCalledTestExceptionResolver();
 		}
 
-		@Bean public BasePackageTestExceptionResolver basePackageTestExceptionResolver() {
+		@Bean
+		public BasePackageTestExceptionResolver basePackageTestExceptionResolver() {
 			return new BasePackageTestExceptionResolver();
 		}
 
-		@Bean public DefaultTestExceptionResolver defaultTestExceptionResolver() {
+		@Bean
+		public DefaultTestExceptionResolver defaultTestExceptionResolver() {
 			return new DefaultTestExceptionResolver();
 		}
 	}

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

@@ -61,6 +61,7 @@ public class DefaultHandlerExceptionResolverTests {
 	@Before
 	public void setUp() {
 		exceptionResolver = new DefaultHandlerExceptionResolver();
+		exceptionResolver.setWarnLogCategory(exceptionResolver.getClass().getName());
 		request = new MockHttpServletRequest();
 		response = new MockHttpServletResponse();
 		request.setMethod("GET");