DelegatingWebMvcConfiguration properly delegates extendHandlerExceptionResolvers

Issue: SPR-14599

Author: jhoeller

spring-webmvc/src/main/java/org/springframework/web/servlet/config/annotation/DelegatingWebMvcConfiguration.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.
@@ -22,14 +22,15 @@
 import org.springframework.context.annotation.Configuration;
 import org.springframework.format.FormatterRegistry;
 import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.util.CollectionUtils;
 import org.springframework.validation.MessageCodesResolver;
 import org.springframework.validation.Validator;
 import org.springframework.web.method.support.HandlerMethodArgumentResolver;
 import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
 import org.springframework.web.servlet.HandlerExceptionResolver;
 
 /**
- * A sub-class of {@code WebMvcConfigurationSupport} that detects and delegates
+ * A subclass of {@code WebMvcConfigurationSupport} that detects and delegates
  * to all beans of type {@link WebMvcConfigurer} allowing them to customize the
  * configuration provided by {@code WebMvcConfigurationSupport}. This is the
  * class actually imported by {@link EnableWebMvc @EnableWebMvc}.
@@ -45,10 +46,9 @@ public class DelegatingWebMvcConfiguration extends WebMvcConfigurationSupport {
 
 	@Autowired(required = false)
 	public void setConfigurers(List<WebMvcConfigurer> configurers) {
-		if (configurers == null || configurers.isEmpty()) {
-			return;
+		if (!CollectionUtils.isEmpty(configurers)) {
+			this.configurers.addWebMvcConfigurers(configurers);
 		}
-		this.configurers.addWebMvcConfigurers(configurers);
 	}
 
 
@@ -132,6 +132,11 @@ protected void configureHandlerExceptionResolvers(List<HandlerExceptionResolver>
 		this.configurers.configureHandlerExceptionResolvers(exceptionResolvers);
 	}
 
+	@Override
+	protected void extendHandlerExceptionResolvers(List<HandlerExceptionResolver> exceptionResolvers) {
+		this.configurers.extendHandlerExceptionResolvers(exceptionResolvers);
+	}
+
 	@Override
 	protected void addCorsMappings(CorsRegistry registry) {
 		this.configurers.addCorsMappings(registry);

spring-webmvc/src/main/java/org/springframework/web/servlet/config/annotation/WebMvcConfigurer.java

@@ -131,11 +131,10 @@ public interface WebMvcConfigurer {
 	void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> exceptionResolvers);
 
 	/**
-	 * A hook for extending or modifying the list of
-	 * {@link HandlerExceptionResolver}s after it has been configured. This may
-	 * be useful for example to allow default resolvers to be registered and then
-	 * insert a custom one through this method.
-	 * @param exceptionResolvers the list of configured resolvers to extend.
+	 * A hook for extending or modifying the list of {@link HandlerExceptionResolver}s
+	 * after it has been configured. This may be useful for example to allow default
+	 * resolvers to be registered and then insert a custom one through this method.
+	 * @param exceptionResolvers the list of configured resolvers to extend
 	 * @since 4.3
 	 */
 	void extendHandlerExceptionResolvers(List<HandlerExceptionResolver> exceptionResolvers);

spring-webmvc/src/main/java/org/springframework/web/servlet/config/annotation/WebMvcConfigurerComposite.java

@@ -109,7 +109,7 @@ public void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> ex
 	@Override
 	public void extendHandlerExceptionResolvers(List<HandlerExceptionResolver> exceptionResolvers) {
 		for (WebMvcConfigurer delegate : this.delegates) {
-			delegate.configureHandlerExceptionResolvers(exceptionResolvers);
+			delegate.extendHandlerExceptionResolvers(exceptionResolvers);
 		}
 	}
 

spring-webmvc/src/test/java/org/springframework/web/servlet/config/annotation/DelegatingWebMvcConfigurationTests.java

@@ -17,7 +17,7 @@
 package org.springframework.web.servlet.config.annotation;
 
 import java.util.ArrayList;
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 
 import org.junit.Before;
@@ -89,10 +89,10 @@ public void setUp() {
 		delegatingConfig = new DelegatingWebMvcConfiguration();
 	}
 
+
 	@Test
 	public void requestMappingHandlerAdapter() throws Exception {
-
-		delegatingConfig.setConfigurers(Arrays.asList(webMvcConfigurer));
+		delegatingConfig.setConfigurers(Collections.singletonList(webMvcConfigurer));
 		RequestMappingHandlerAdapter adapter = delegatingConfig.requestMappingHandlerAdapter();
 
 		ConfigurableWebBindingInitializer initializer = (ConfigurableWebBindingInitializer) adapter.getWebBindingInitializer();
@@ -141,7 +141,7 @@ public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
 	public void getCustomValidator() {
 		given(webMvcConfigurer.getValidator()).willReturn(new LocalValidatorFactoryBean());
 
-		delegatingConfig.setConfigurers(Arrays.asList(webMvcConfigurer));
+		delegatingConfig.setConfigurers(Collections.singletonList(webMvcConfigurer));
 		delegatingConfig.mvcValidator();
 
 		verify(webMvcConfigurer).getValidator();
@@ -151,16 +151,15 @@ public void getCustomValidator() {
 	public void getCustomMessageCodesResolver() {
 		given(webMvcConfigurer.getMessageCodesResolver()).willReturn(new DefaultMessageCodesResolver());
 
-		delegatingConfig.setConfigurers(Arrays.asList(webMvcConfigurer));
+		delegatingConfig.setConfigurers(Collections.singletonList(webMvcConfigurer));
 		delegatingConfig.getMessageCodesResolver();
 
 		verify(webMvcConfigurer).getMessageCodesResolver();
 	}
 
 	@Test
 	public void handlerExceptionResolver() throws Exception {
-
-		delegatingConfig.setConfigurers(Arrays.asList(webMvcConfigurer));
+		delegatingConfig.setConfigurers(Collections.singletonList(webMvcConfigurer));
 		delegatingConfig.handlerExceptionResolver();
 
 		verify(webMvcConfigurer).configureMessageConverters(converters.capture());
@@ -186,7 +185,7 @@ public void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> ex
 		delegatingConfig.setConfigurers(configurers);
 
 		HandlerExceptionResolverComposite composite =
-			(HandlerExceptionResolverComposite) delegatingConfig.handlerExceptionResolver();
+				(HandlerExceptionResolverComposite) delegatingConfig.handlerExceptionResolver();
 		assertEquals("Only one custom converter is expected", 1, composite.getExceptionResolvers().size());
 	}
 
@@ -200,9 +199,9 @@ public void configurePathMatch() throws Exception {
 			@Override
 			public void configurePathMatch(PathMatchConfigurer configurer) {
 				configurer.setUseRegisteredSuffixPatternMatch(true)
-					.setUseTrailingSlashMatch(false)
-					.setUrlPathHelper(pathHelper)
-					.setPathMatcher(pathMatcher);
+						.setUseTrailingSlashMatch(false)
+						.setUrlPathHelper(pathHelper)
+						.setPathMatcher(pathMatcher);
 			}
 		});
 		delegatingConfig.setConfigurers(configurers);