Support @RestControllerAdvice in Standalone MockMvc again

Since Spring Framework 5.2, @RestControllerAdvice registered with
MockMvc when using MockMvcBuilders.standaloneSetup() has no longer been
properly supported if annotation attributes were declared in the
@RestControllerAdvice annotation. Prior to 5.2, this was not an issue.

The cause for this regression is two-fold.

1. Commit 50c257794f refactored
   DefaultListableBeanFactory so that findAnnotationOnBean() supports
   merged annotations; however, that commit did not refactor
   StaticListableBeanFactory#findAnnotationOnBean() to support merged
   annotations.

2. Commit 978adbdae7 refactored
   ControllerAdviceBean so that a merged @ControllerAdvice annotation
   is only looked up via ApplicationContext#findAnnotationOnBean().

The latter relies on the fact that findAnnotationOnBean() supports
merged annotations (e.g., @RestControllerAdvice as a merged instance of
@ControllerAdvice). Behind the scenes, MockMvcBuilders.standaloneSetup()
creates a StubWebApplicationContext which internally uses a
StubBeanFactory which extends StaticListableBeanFactory. Consequently,
since the implementation of findAnnotationOnBean() in
StaticListableBeanFactory was not updated to support merged annotations
like it was in DefaultListableBeanFactory, we only see this regression
with the standalone MockMvc support and not with MockMvc support for an
existing WebApplicationContext or with standard Spring applications
using an ApplicationContext that uses DefaultListableBeanFactory.

This commit fixes this regression by supporting merged annotations in
StaticListableBeanFactory#findAnnotationOnBean() as well.

Closes gh-25520

spring-beans/src/main/java/org/springframework/beans/factory/support/StaticListableBeanFactory.java

@@ -37,7 +37,7 @@ import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.beans.factory.SmartFactoryBean;
 import org.springframework.core.OrderComparator;
 import org.springframework.core.ResolvableType;
-import org.springframework.core.annotation.AnnotationUtils;
+import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
@@ -450,7 +450,7 @@ public class StaticListableBeanFactory implements ListableBeanFactory {
 			throws NoSuchBeanDefinitionException {
 
 		Class<?> beanType = getType(beanName);
-		return (beanType != null ? AnnotationUtils.findAnnotation(beanType, annotationType) : null);
+		return (beanType != null ? AnnotatedElementUtils.findMergedAnnotation(beanType, annotationType) : null);
 	}
 
 }

spring-beans/src/test/java/org/springframework/beans/factory/BeanFactoryUtilsTests.java

@@ -16,6 +16,8 @@
 
 package org.springframework.beans.factory;
 
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
@@ -33,6 +35,7 @@ import org.springframework.beans.testfixture.beans.TestAnnotation;
 import org.springframework.beans.testfixture.beans.TestBean;
 import org.springframework.beans.testfixture.beans.factory.DummyFactory;
 import org.springframework.cglib.proxy.NoOp;
+import org.springframework.core.annotation.AliasFor;
 import org.springframework.core.io.Resource;
 import org.springframework.util.ObjectUtils;
 
@@ -324,6 +327,33 @@ public class BeanFactoryUtilsTests {
 		assertThat(Arrays.equals(new String[] { "buffer" }, deps)).isTrue();
 	}
 
+	@Test
+	public void findAnnotationOnBean() {
+		this.listableBeanFactory.registerSingleton("controllerAdvice", new ControllerAdviceClass());
+		this.listableBeanFactory.registerSingleton("restControllerAdvice", new RestControllerAdviceClass());
+		testFindAnnotationOnBean(this.listableBeanFactory);
+	}
+
+	@Test  // gh-25520
+	public void findAnnotationOnBeanWithStaticFactory() {
+		StaticListableBeanFactory lbf = new StaticListableBeanFactory();
+		lbf.addBean("controllerAdvice", new ControllerAdviceClass());
+		lbf.addBean("restControllerAdvice", new RestControllerAdviceClass());
+		testFindAnnotationOnBean(lbf);
+	}
+
+	private void testFindAnnotationOnBean(ListableBeanFactory lbf) {
+		assertControllerAdvice(lbf, "controllerAdvice");
+		assertControllerAdvice(lbf, "restControllerAdvice");
+	}
+
+	private void assertControllerAdvice(ListableBeanFactory lbf, String beanName) {
+		ControllerAdvice controllerAdvice = lbf.findAnnotationOnBean(beanName, ControllerAdvice.class);
+		assertThat(controllerAdvice).isNotNull();
+		assertThat(controllerAdvice.value()).isEqualTo("com.example");
+		assertThat(controllerAdvice.basePackage()).isEqualTo("com.example");
+	}
+
 	@Test
 	public void isSingletonAndIsPrototypeWithStaticFactory() {
 		StaticListableBeanFactory lbf = new StaticListableBeanFactory();
@@ -393,6 +423,35 @@ public class BeanFactoryUtilsTests {
 	}
 
 
+	@Retention(RetentionPolicy.RUNTIME)
+	@interface ControllerAdvice {
+
+		@AliasFor("basePackage")
+		String value() default "";
+
+		@AliasFor("value")
+		String basePackage() default "";
+	}
+
+	@Retention(RetentionPolicy.RUNTIME)
+	@ControllerAdvice
+	@interface RestControllerAdvice {
+
+		@AliasFor(annotation = ControllerAdvice.class)
+		String value() default "";
+
+		@AliasFor(annotation = ControllerAdvice.class)
+		String basePackage() default "";
+	}
+
+	@ControllerAdvice("com.example")
+	static class ControllerAdviceClass {
+	}
+
+	@RestControllerAdvice("com.example")
+	static class RestControllerAdviceClass {
+	}
+
 	static class TestBeanSmartFactoryBean implements SmartFactoryBean<TestBean> {
 
 		private final TestBean testBean = new TestBean("enigma", 42);

spring-test/src/test/java/org/springframework/test/web/servlet/samples/standalone/ExceptionHandlerTests.java

@@ -16,16 +16,23 @@
 
 package org.springframework.test.web.servlet.samples.standalone;
 
+import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 
+import org.springframework.core.Ordered;
+import org.springframework.core.annotation.Order;
+import org.springframework.http.MediaType;
 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.ControllerAdvice;
 import org.springframework.web.bind.annotation.ExceptionHandler;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.bind.annotation.RestControllerAdvice;
 
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.forwardedUrl;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
 import static org.springframework.test.web.servlet.setup.MockMvcBuilders.standaloneSetup;
 
@@ -37,28 +44,32 @@ import static org.springframework.test.web.servlet.setup.MockMvcBuilders.standal
  */
 class ExceptionHandlerTests {
 
-	@Test
-	void localExceptionHandlerMethod() throws Exception {
-		standaloneSetup(new PersonController()).build()
-			.perform(get("/person/Clyde"))
+	@Nested
+	class MvcTests {
+
+		@Test
+		void localExceptionHandlerMethod() throws Exception {
+			standaloneSetup(new PersonController()).build()
+				.perform(get("/person/Clyde"))
 				.andExpect(status().isOk())
 				.andExpect(forwardedUrl("errorView"));
-	}
+		}
 
-	@Test
-	void globalExceptionHandlerMethod() throws Exception {
-		standaloneSetup(new PersonController()).setControllerAdvice(new GlobalExceptionHandler()).build()
+		@Test
+		void globalExceptionHandlerMethod() throws Exception {
+			standaloneSetup(new PersonController()).setControllerAdvice(new GlobalExceptionHandler()).build()
 				.perform(get("/person/Bonnie"))
 				.andExpect(status().isOk())
 				.andExpect(forwardedUrl("globalErrorView"));
-	}
+		}
 
-	@Test
-	void globalExceptionHandlerMethodUsingClassArgument() throws Exception {
-		standaloneSetup(PersonController.class).setControllerAdvice(GlobalExceptionHandler.class).build()
+		@Test
+		void globalExceptionHandlerMethodUsingClassArgument() throws Exception {
+			standaloneSetup(PersonController.class).setControllerAdvice(GlobalExceptionHandler.class).build()
 				.perform(get("/person/Bonnie"))
 				.andExpect(status().isOk())
 				.andExpect(forwardedUrl("globalErrorView"));
+		}
 	}
 
 
@@ -82,7 +93,6 @@ class ExceptionHandlerTests {
 		}
 	}
 
-
 	@ControllerAdvice
 	private static class GlobalExceptionHandler {
 
@@ -92,4 +102,124 @@ class ExceptionHandlerTests {
 		}
 	}
 
+
+	@Nested
+	class RestTests {
+
+		@Test
+		void noException() throws Exception {
+			standaloneSetup(RestPersonController.class)
+				.setControllerAdvice(RestGlobalExceptionHandler.class, RestPersonControllerExceptionHandler.class).build()
+				.perform(get("/person/Yoda").accept(MediaType.APPLICATION_JSON))
+				.andExpect(status().isOk())
+				.andExpect(jsonPath("$.name").value("Yoda"));
+		}
+
+		@Test
+		void localExceptionHandlerMethod() throws Exception {
+			standaloneSetup(RestPersonController.class)
+				.setControllerAdvice(RestGlobalExceptionHandler.class, RestPersonControllerExceptionHandler.class).build()
+				.perform(get("/person/Luke").accept(MediaType.APPLICATION_JSON))
+				.andExpect(status().isOk())
+				.andExpect(jsonPath("$.error").value("local - IllegalArgumentException"));
+		}
+
+		@Test
+		void globalExceptionHandlerMethod() throws Exception {
+			standaloneSetup(RestPersonController.class)
+				.setControllerAdvice(RestGlobalExceptionHandler.class).build()
+				.perform(get("/person/Leia").accept(MediaType.APPLICATION_JSON))
+				.andExpect(status().isOk())
+				.andExpect(jsonPath("$.error").value("global - IllegalStateException"));
+		}
+
+		@Test
+		void globalRestPersonControllerExceptionHandlerTakesPrecedenceOverGlobalExceptionHandler() throws Exception {
+			standaloneSetup(RestPersonController.class)
+				.setControllerAdvice(RestGlobalExceptionHandler.class, RestPersonControllerExceptionHandler.class).build()
+				.perform(get("/person/Leia").accept(MediaType.APPLICATION_JSON))
+				.andExpect(status().isOk())
+				.andExpect(jsonPath("$.error").value("globalPersonController - IllegalStateException"));
+		}
+
+		@Test  // gh-25520
+		void noHandlerFound() throws Exception {
+			standaloneSetup(RestPersonController.class)
+				.setControllerAdvice(RestGlobalExceptionHandler.class, RestPersonControllerExceptionHandler.class)
+				.addDispatcherServletCustomizer(dispatcherServlet -> dispatcherServlet.setThrowExceptionIfNoHandlerFound(true))
+				.build()
+				.perform(get("/bogus").accept(MediaType.APPLICATION_JSON))
+				.andExpect(status().isOk())
+				.andExpect(jsonPath("$.error").value("global - NoHandlerFoundException"));
+		}
+	}
+
+
+	@RestController
+	private static class RestPersonController {
+
+		@GetMapping("/person/{name}")
+		Person get(@PathVariable String name) {
+			switch (name) {
+				case "Luke":
+					throw new IllegalArgumentException();
+				case "Leia":
+					throw new IllegalStateException();
+				default:
+					return new Person("Yoda");
+			}
+		}
+
+		@ExceptionHandler
+		Error handleException(IllegalArgumentException exception) {
+			return new Error("local - " + exception.getClass().getSimpleName());
+		}
+	}
+
+	@RestControllerAdvice(assignableTypes = RestPersonController.class)
+	@Order(Ordered.HIGHEST_PRECEDENCE)
+	private static class RestPersonControllerExceptionHandler {
+
+		@ExceptionHandler
+		Error handleException(Throwable exception) {
+			return new Error("globalPersonController - " + exception.getClass().getSimpleName());
+		}
+	}
+
+	@RestControllerAdvice
+	@Order(Ordered.LOWEST_PRECEDENCE)
+	private static class RestGlobalExceptionHandler {
+
+		@ExceptionHandler
+		Error handleException(Throwable exception) {
+			return new Error( "global - " + exception.getClass().getSimpleName());
+		}
+	}
+
+	static class Person {
+
+		private final String name;
+
+		Person(String name) {
+			this.name = name;
+		}
+
+		public String getName() {
+			return name;
+		}
+	}
+
+	static class Error {
+
+		private final String error;
+
+		Error(String error) {
+			this.error = error;
+		}
+
+		public String getError() {
+			return error;
+		}
+	}
+
 }