Support <ref> for arg resolvers return value handlers

Issue: SPR-11927

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

@@ -471,21 +471,34 @@ class AnnotationDrivenBeanDefinitionParser implements BeanDefinitionParser {
 	private ManagedList<?> getArgumentResolvers(Element element, ParserContext parserContext) {
 		Element resolversElement = DomUtils.getChildElementByTagName(element, "argument-resolvers");
 		if (resolversElement != null) {
-			ManagedList<BeanDefinitionHolder> argumentResolvers = extractBeanSubElements(resolversElement, parserContext);
-            ManagedList<BeanMetadataElement> customAndReferencedResolvers = new ManagedList<BeanMetadataElement>();
-            customAndReferencedResolvers.addAll(wrapWebArgumentResolverBeanDefs(argumentResolvers, parserContext));
-            customAndReferencedResolvers.addAll(extractBeanRefSubElements(resolversElement, parserContext));
-            return customAndReferencedResolvers;
+			ManagedList<Object> resolvers = extractBeanSubElements(resolversElement, parserContext);
+			return wrapLegacyResolvers(resolvers, parserContext);
 		}
 		return null;
 	}
 
-	private ManagedList<?> getReturnValueHandlers(Element element, ParserContext parserContext) {
-		Element handlersElement = DomUtils.getChildElementByTagName(element, "return-value-handlers");
-		if (handlersElement != null) {
-			return extractBeanSubElements(handlersElement, parserContext);
+	private ManagedList<Object> wrapLegacyResolvers(List<Object> list, ParserContext context) {
+		ManagedList<Object> result = new ManagedList<Object>();
+		for (Object object : list) {
+			if (object instanceof BeanDefinitionHolder) {
+				BeanDefinitionHolder beanDef = (BeanDefinitionHolder) object;
+				String className = beanDef.getBeanDefinition().getBeanClassName();
+				Class<?> clazz = ClassUtils.resolveClassName(className, context.getReaderContext().getBeanClassLoader());
+				if (WebArgumentResolver.class.isAssignableFrom(clazz)) {
+					RootBeanDefinition adapter = new RootBeanDefinition(ServletWebArgumentResolverAdapter.class);
+					adapter.getConstructorArgumentValues().addIndexedArgumentValue(0, beanDef);
+					result.add(new BeanDefinitionHolder(adapter, beanDef.getBeanName() + "Adapter"));
+					continue;
+				}
+			}
+			result.add(object);
 		}
-		return null;
+		return result;
+	}
+
+	private ManagedList<?> getReturnValueHandlers(Element element, ParserContext parserContext) {
+		Element handlers = DomUtils.getChildElementByTagName(element, "return-value-handlers");
+		return (handlers != null ? extractBeanSubElements(handlers, parserContext) : null);
 	}
 
 	private ManagedList<?> getMessageConverters(Element element, Object source, ParserContext parserContext) {
@@ -536,13 +549,12 @@ class AnnotationDrivenBeanDefinitionParser implements BeanDefinitionParser {
 	}
 
 
-	private ManagedList<BeanDefinitionHolder> extractBeanSubElements(Element parentElement, ParserContext parserContext) {
-		ManagedList<BeanDefinitionHolder> list = new ManagedList<BeanDefinitionHolder>();
+	private ManagedList<Object> extractBeanSubElements(Element parentElement, ParserContext parserContext) {
+		ManagedList<Object> list = new ManagedList<Object>();
 		list.setSource(parserContext.extractSource(parentElement));
-		for (Element beanElement : DomUtils.getChildElementsByTagName(parentElement, "bean")) {
-			BeanDefinitionHolder beanDef = parserContext.getDelegate().parseBeanDefinitionElement(beanElement);
-			beanDef = parserContext.getDelegate().decorateBeanDefinitionIfRequired(beanElement, beanDef);
-			list.add(beanDef);
+		for (Element beanElement : DomUtils.getChildElementsByTagName(parentElement, "bean", "ref")) {
+			Object object = parserContext.getDelegate().parsePropertySubElement(beanElement, null);
+			list.add(object);
 		}
 		return list;
 	}
@@ -566,25 +578,6 @@ class AnnotationDrivenBeanDefinitionParser implements BeanDefinitionParser {
         return list;
     }
 
-	private ManagedList<BeanDefinitionHolder> wrapWebArgumentResolverBeanDefs(
-			List<BeanDefinitionHolder> beanDefs, ParserContext parserContext) {
-
-		ManagedList<BeanDefinitionHolder> result = new ManagedList<BeanDefinitionHolder>();
-		for (BeanDefinitionHolder beanDef : beanDefs) {
-			String className = beanDef.getBeanDefinition().getBeanClassName();
-			Class<?> clazz = ClassUtils.resolveClassName(className, parserContext.getReaderContext().getBeanClassLoader());
-			if (WebArgumentResolver.class.isAssignableFrom(clazz)) {
-				RootBeanDefinition adapter = new RootBeanDefinition(ServletWebArgumentResolverAdapter.class);
-				adapter.getConstructorArgumentValues().addIndexedArgumentValue(0, beanDef);
-				result.add(new BeanDefinitionHolder(adapter, beanDef.getBeanName() + "Adapter"));
-			}
-			else {
-				result.add(beanDef);
-			}
-		}
-		return result;
-	}
-
 
 	/**
 	 * A FactoryBean for a CompositeUriComponentsContributor that obtains the

spring-webmvc/src/main/resources/org/springframework/web/servlet/config/spring-mvc-4.1.xsd

@@ -138,8 +138,7 @@
 							<xsd:element ref="beans:ref" minOccurs="0" maxOccurs="unbounded">
 								<xsd:annotation>
 									<xsd:documentation><![CDATA[
-	A reference to a HandlerMethodArgumentResolver bean definition. Expects a HandlerMethodArgumentResolver instance,
-	 WebArgumentResolver instances has to be wrapped with a ServletWebArgumentResolverAdapter
+	A reference to a HandlerMethodArgumentResolver bean definition.
 									]]></xsd:documentation>
 									<xsd:appinfo>
 										<tool:annotation kind="ref">
@@ -160,15 +159,27 @@
 						]]></xsd:documentation>
 					</xsd:annotation>
 					<xsd:complexType>
-						<xsd:sequence>
-							<xsd:element ref="beans:bean" minOccurs="1" maxOccurs="unbounded">
+						<xsd:choice minOccurs="1" maxOccurs="unbounded">
+							<xsd:element ref="beans:bean" minOccurs="0" maxOccurs="unbounded">
 								<xsd:annotation>
 									<xsd:documentation><![CDATA[
 	The HandlerMethodReturnValueHandler bean definition.
 									]]></xsd:documentation>
 								</xsd:annotation>
 							</xsd:element>
-						</xsd:sequence>
+							<xsd:element ref="beans:ref" minOccurs="0" maxOccurs="unbounded">
+								<xsd:annotation>
+									<xsd:documentation><![CDATA[
+	A reference to a HandlerMethodReturnValueHandler bean definition.
+									]]></xsd:documentation>
+									<xsd:appinfo>
+										<tool:annotation kind="ref">
+											<tool:expected-type type="java:org.springframework.web.method.support.HandlerMethodReturnValueHandler" />
+										</tool:annotation>
+									</xsd:appinfo>
+								</xsd:annotation>
+							</xsd:element>
+						</xsd:choice>
 					</xsd:complexType>
 				</xsd:element>
 				<xsd:element name="async-support" minOccurs="0">

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

@@ -117,26 +117,13 @@ public class AnnotationDrivenBeanDefinitionParserTests {
 		assertNotNull(value);
 		assertTrue(value instanceof List);
 		List<HandlerMethodArgumentResolver> resolvers = (List<HandlerMethodArgumentResolver>) value;
-		assertEquals(2, resolvers.size());
+		assertEquals(3, resolvers.size());
 		assertTrue(resolvers.get(0) instanceof ServletWebArgumentResolverAdapter);
 		assertTrue(resolvers.get(1) instanceof TestHandlerMethodArgumentResolver);
+		assertTrue(resolvers.get(2) instanceof TestHandlerMethodArgumentResolver);
+		assertNotSame(resolvers.get(1), resolvers.get(2));
 	}
 
-    @SuppressWarnings("unchecked")
-    @Test
-    public void testArgumentResolversWithReference() {
-        loadBeanDefinitions("mvc-config-argument-resolvers-references.xml");
-        RequestMappingHandlerAdapter adapter = appContext.getBean(RequestMappingHandlerAdapter.class);
-        assertNotNull(adapter);
-        Object value = new DirectFieldAccessor(adapter).getPropertyValue("customArgumentResolvers");
-        assertNotNull(value);
-        assertTrue(value instanceof List);
-        List<HandlerMethodArgumentResolver> resolvers = (List<HandlerMethodArgumentResolver>) value;
-        assertEquals(2, resolvers.size());
-        assertTrue(resolvers.get(0) instanceof ServletWebArgumentResolverAdapter);
-        assertTrue(resolvers.get(1) instanceof TestHandlerMethodArgumentResolver);
-    }
-
 	@SuppressWarnings("unchecked")
 	@Test
 	public void testReturnValueHandlers() {
@@ -147,8 +134,10 @@ public class AnnotationDrivenBeanDefinitionParserTests {
 		assertNotNull(value);
 		assertTrue(value instanceof List);
 		List<HandlerMethodReturnValueHandler> handlers = (List<HandlerMethodReturnValueHandler>) value;
-		assertEquals(1, handlers.size());
+		assertEquals(2, handlers.size());
 		assertEquals(TestHandlerMethodReturnValueHandler.class, handlers.get(0).getClass());
+		assertEquals(TestHandlerMethodReturnValueHandler.class, handlers.get(1).getClass());
+		assertNotSame(handlers.get(0), handlers.get(1));
 	}
 
 	@Test

spring-webmvc/src/test/resources/org/springframework/web/servlet/config/mvc-config-argument-resolvers-references.xml

@@ -1,17 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<beans xmlns="http://www.springframework.org/schema/beans"
-	xmlns:mvc="http://www.springframework.org/schema/mvc"
-	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
-		http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">
-
-	<mvc:annotation-driven>
-		<mvc:argument-resolvers>
-			<bean class="org.springframework.web.servlet.config.TestWebArgumentResolver"/>
-			<ref bean="customArgumentResolver" />
-		</mvc:argument-resolvers>
-	</mvc:annotation-driven>
-
-	<bean id="customArgumentResolver" class="org.springframework.web.servlet.config.TestHandlerMethodArgumentResolver"/>
-
-</beans>

spring-webmvc/src/test/resources/org/springframework/web/servlet/config/mvc-config-argument-resolvers.xml

@@ -9,7 +9,10 @@
 		<mvc:argument-resolvers>
 			<bean class="org.springframework.web.servlet.config.TestWebArgumentResolver"/>
 			<bean class="org.springframework.web.servlet.config.TestHandlerMethodArgumentResolver"/>
+            <ref bean="customArgumentResolver" />
 		</mvc:argument-resolvers>
 	</mvc:annotation-driven>
 
+    <bean id="customArgumentResolver" class="org.springframework.web.servlet.config.TestHandlerMethodArgumentResolver"/>
+
 </beans>

spring-webmvc/src/test/resources/org/springframework/web/servlet/config/mvc-config-return-value-handlers.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <beans xmlns="http://www.springframework.org/schema/beans"
-    xmlns:mvc="http://www.springframework.org/schema/mvc"
+	xmlns:mvc="http://www.springframework.org/schema/mvc"
 	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
 		http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">
@@ -8,7 +8,10 @@
 	<mvc:annotation-driven>
 		<mvc:return-value-handlers>
 			<bean class="org.springframework.web.servlet.config.TestHandlerMethodReturnValueHandler"/>
+			<ref bean="customHandler" />
 		</mvc:return-value-handlers>
 	</mvc:annotation-driven>
 
+	<bean id="customHandler" class="org.springframework.web.servlet.config.TestHandlerMethodReturnValueHandler"/>
+
 </beans>