Support Ordered interface for @ControllerAdvice beans

Closes gh-23163

Author: sbrannen

spring-web/src/main/java/org/springframework/web/bind/annotation/ControllerAdvice.java

@@ -33,15 +33,15 @@
  * multiple {@code @Controller} classes.
  *
  * <p>Classes with {@code @ControllerAdvice} can be declared explicitly as Spring
- * beans or auto-detected via classpath scanning. All such beans are sorted via
- * {@link org.springframework.core.annotation.AnnotationAwareOrderComparator
- * AnnotationAwareOrderComparator}, based on
- * {@link org.springframework.core.annotation.Order @Order} and
- * {@link org.springframework.core.Ordered Ordered}, and applied in that order
- * at runtime. For handling exceptions, an {@code @ExceptionHandler} will be
- * picked on the first advice with a matching exception handler method. For
- * model attributes and {@code InitBinder} initialization, {@code @ModelAttribute}
- * and {@code @InitBinder} methods will also follow {@code @ControllerAdvice} order.
+ * beans or auto-detected via classpath scanning. All such beans are sorted based
+ * on {@link org.springframework.core.Ordered Ordered},
+ * {@link org.springframework.core.annotation.Order @Order}, and
+ * {@link javax.annotation.Priority @Priority} (in that order of precedence),
+ * and applied in that order at runtime. For handling exceptions, an
+ * {@code @ExceptionHandler} will be picked on the first advice with a matching
+ * exception handler method. For model attributes and {@code InitBinder}
+ * initialization, {@code @ModelAttribute} and {@code @InitBinder} methods will
+ * also follow {@code @ControllerAdvice} order.
  *
  * <p>Note: For {@code @ExceptionHandler} methods, a root exception match will be
  * preferred to just matching a cause of the current exception, among the handler

spring-web/src/main/java/org/springframework/web/method/ControllerAdviceBean.java

@@ -67,7 +67,8 @@ public class ControllerAdviceBean implements Ordered {
 	@Nullable
 	private final BeanFactory beanFactory;
 
-	private final int order;
+	@Nullable
+	private Integer order;
 
 
 	/**
@@ -81,7 +82,6 @@ public ControllerAdviceBean(Object bean) {
 		this.beanType = ClassUtils.getUserClass(bean.getClass());
 		this.beanTypePredicate = createBeanTypePredicate(this.beanType);
 		this.beanFactory = null;
-		this.order = initOrderFromBean(bean);
 	}
 
 	/**
@@ -117,16 +117,32 @@ public ControllerAdviceBean(String beanName, BeanFactory beanFactory, @Nullable
 		this.beanTypePredicate = (controllerAdvice != null ? createBeanTypePredicate(controllerAdvice)
 				: createBeanTypePredicate(this.beanType));
 		this.beanFactory = beanFactory;
-		this.order = initOrderFromBeanType(this.beanType);
 	}
 
 
 	/**
-	 * Return the order value extracted from the {@link ControllerAdvice}
-	 * annotation, or {@link Ordered#LOWEST_PRECEDENCE} otherwise.
+	 * Get the order value for the contained bean.
+	 * <p>As of Spring Framework 5.2, the order value is lazily retrieved using
+	 * the following algorithm and cached.
+	 * <ul>
+	 * <li>If the {@linkplain #resolveBean resolved bean} implements {@link Ordered},
+	 * use the value returned by {@link Ordered#getOrder()}.</li>
+	 * <li>Otherwise use the value returned by {@link OrderUtils#getOrder(Class, int)}
+	 * with {@link Ordered#LOWEST_PRECEDENCE} used as the default order value.</li>
+	 * </ul>
+	 * @see #resolveBean()
 	 */
 	@Override
 	public int getOrder() {
+		if (this.order == null) {
+			Object resolvedBean = resolveBean();
+			if (resolvedBean instanceof Ordered) {
+				this.order = ((Ordered) resolvedBean).getOrder();
+			}
+			else {
+				this.order = OrderUtils.getOrder(getBeanType(), Ordered.LOWEST_PRECEDENCE);
+			}
+		}
 		return this.order;
 	}
 
@@ -236,16 +252,4 @@ private static HandlerTypePredicate createBeanTypePredicate(ControllerAdvice con
 		return HandlerTypePredicate.forAnyHandlerType();
 	}
 
-	private static int initOrderFromBean(Object bean) {
-		return (bean instanceof Ordered ? ((Ordered) bean).getOrder() : initOrderFromBeanType(bean.getClass()));
-	}
-
-	private static int initOrderFromBeanType(@Nullable Class<?> beanType) {
-		Integer order = null;
-		if (beanType != null) {
-			order = OrderUtils.getOrder(beanType);
-		}
-		return (order != null ? order : Ordered.LOWEST_PRECEDENCE);
-	}
-
 }

spring-web/src/test/java/org/springframework/web/method/ControllerAdviceBeanTests.java

@@ -22,6 +22,7 @@
 
 import org.junit.Test;
 
+import org.springframework.beans.BeanUtils;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
@@ -32,7 +33,6 @@
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.mockito.BDDMockito.given;
 import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 
 /**
@@ -103,8 +103,7 @@ public void orderedWithLowestPrecedenceByDefaultForBeanInstance() {
 
 	@Test
 	public void orderedViaOrderedInterfaceForBeanName() {
-		// TODO Change expectedOrder once Ordered is properly supported
-		assertOrder(OrderedControllerAdvice.class, Ordered.LOWEST_PRECEDENCE);
+		assertOrder(OrderedControllerAdvice.class, 42);
 	}
 
 	@Test
@@ -211,15 +210,14 @@ private void assertOrder(Class beanType, int expectedOrder) {
 		BeanFactory beanFactory = mock(BeanFactory.class);
 		given(beanFactory.containsBean(beanName)).willReturn(true);
 		given(beanFactory.getType(beanName)).willReturn(beanType);
+		given(beanFactory.getBean(beanName)).willReturn(BeanUtils.instantiateClass(beanType));
 
 		ControllerAdviceBean controllerAdviceBean = new ControllerAdviceBean(beanName, beanFactory);
 
 		assertThat(controllerAdviceBean.getOrder()).isEqualTo(expectedOrder);
 		verify(beanFactory).containsBean(beanName);
 		verify(beanFactory).getType(beanName);
-		// Expecting 0 invocations of getBean() since Ordered is not yet supported.
-		// TODO Change expected number of invocations once Ordered is properly supported
-		verify(beanFactory, times(0)).getBean(beanName);
+		verify(beanFactory).getBean(beanName);
 	}
 
 	private void assertApplicable(String message, ControllerAdviceBean controllerAdvice, Class<?> controllerBeanType) {