Detect Order on target class as well

Previously, the `@Order` annotation was managed in an inconsistent way
when placed at the implementation level. For simple beans, it was
discovered properly but wasn't for beans requiring a proxy.

OrderComparator.SourceProvider now explicitly allows to return several
order sources; the default implementation returns not only the factory
method (if  any) but also the target class if it happens to be different
from the class of the bean.

Issue: SPR-12636

spring-core/src/main/java/org/springframework/core/OrderComparator.java

@@ -21,6 +21,8 @@ import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 
+import org.springframework.util.ObjectUtils;
+
 /**
  * {@link Comparator} implementation for {@link Ordered} objects,
  * sorting by order value ascending (resp. by priority descending).
@@ -89,7 +91,19 @@ public class OrderComparator implements Comparator<Object> {
 	private int getOrder(Object obj, OrderSourceProvider sourceProvider) {
 		Integer order = null;
 		if (sourceProvider != null) {
-			order = findOrder(sourceProvider.getOrderSource(obj));
+			Object orderSource = sourceProvider.getOrderSource(obj);
+			if (orderSource != null && orderSource.getClass().isArray()) {
+				Object[] sources = ObjectUtils.toObjectArray(orderSource);
+				for (Object source : sources) {
+					order = findOrder(source);
+					if (order != null) {
+						break;
+					}
+				}
+			}
+			else {
+				order = findOrder(orderSource);
+			}
 		}
 		return (order != null ? order : getOrder(obj));
 	}
@@ -186,6 +200,7 @@ public class OrderComparator implements Comparator<Object> {
 		/**
 		 * Return an order source for the specified object, i.e. an object that
 		 * should be checked for an order value as a replacement to the given object.
+		 * <p>Can also be an array of order source objects.
 		 * <p>If the returned object does not indicate any order, the comparator
 		 * will fall back to checking the original object.
 		 * @param obj the object to find an order source for

spring-core/src/test/java/org/springframework/core/OrderComparatorTests.java

@@ -18,43 +18,90 @@ package org.springframework.core;
 
 import java.util.Comparator;
 
-import junit.framework.TestCase;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
 
 /**
  * Unit tests for the {@link OrderComparator} class.
  *
  * @author Rick Evans
+ * @author Stephane Nicoll
  */
-public final class OrderComparatorTests extends TestCase {
+public final class OrderComparatorTests {
 
-	private Comparator comparator;
+	private final OrderComparator comparator = new OrderComparator();
 
-
-	@Override
-	protected void setUp() throws Exception {
-		this.comparator = new OrderComparator();
-	}
-
-
-	public void testCompareOrderedInstancesBefore() throws Exception {
+	@Test
+	public void compareOrderedInstancesBefore() {
 		assertEquals(-1, this.comparator.compare(
 				new StubOrdered(100), new StubOrdered(2000)));
 	}
 
-	public void testCompareOrderedInstancesSame() throws Exception {
+	@Test
+	public void compareOrderedInstancesSame() {
 		assertEquals(0, this.comparator.compare(
 				new StubOrdered(100), new StubOrdered(100)));
 	}
 
-	public void testCompareOrderedInstancesAfter() throws Exception {
+	@Test
+	public void compareOrderedInstancesAfter() {
 		assertEquals(1, this.comparator.compare(
 				new StubOrdered(982300), new StubOrdered(100)));
 	}
 
-	public void testCompareTwoNonOrderedInstancesEndsUpAsSame() throws Exception {
+	@Test
+	public void compareTwoNonOrderedInstancesEndsUpAsSame() {
 		assertEquals(0, this.comparator.compare(new Object(), new Object()));
 	}
 
+	@Test
+	public void compareWithSimpleSourceProvider() {
+		Comparator<Object> customComparator = this.comparator.withSourceProvider(
+				new TestSourceProvider(5L, new StubOrdered(25)));
+		assertEquals(-1, customComparator.compare(new StubOrdered(10), 5L));
+	}
+
+	@Test
+	public void compareWithSourceProviderArray() {
+		Comparator<Object> customComparator = this.comparator.withSourceProvider(
+				new TestSourceProvider(5L, new Object[] {new StubOrdered(10), new StubOrdered(-25)}));
+		assertEquals(-1, customComparator.compare(5L, new Object()));
+	}
+
+	@Test
+	public void compareWithSourceProviderArrayNoMatch() {
+		Comparator<Object> customComparator = this.comparator.withSourceProvider(
+				new TestSourceProvider(5L, new Object[]{new Object(), new Object()}));
+		assertEquals(0, customComparator.compare(new Object(), 5L));
+	}
+
+	@Test
+	public void compareWithSourceProviderEmpty() {
+		Comparator<Object> customComparator = this.comparator.withSourceProvider(
+				new TestSourceProvider(50L, new Object()));
+		assertEquals(0, customComparator.compare(new Object(), 5L));
+	}
+
+
+	private static final class TestSourceProvider implements OrderComparator.OrderSourceProvider {
+
+		private final Object target;
+		private final Object orderSource;
+
+		public TestSourceProvider(Object target, Object orderSource) {
+			this.target = target;
+			this.orderSource = orderSource;
+		}
+
+		@Override
+		public Object getOrderSource(Object obj) {
+			if (target.equals(obj)) {
+				return orderSource;
+			}
+			return null;
+		}
+	}
 
 	private static final class StubOrdered implements Ordered {