(AnnotationAware)OrderComparator supports null values again

Issue: SPR-15823

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -65,11 +65,11 @@ public class OrderComparator implements Comparator<Object> {
 	}
 
 	@Override
-	public int compare(Object o1, Object o2) {
+	public int compare(@Nullable Object o1, @Nullable Object o2) {
 		return doCompare(o1, o2, null);
 	}
 
-	private int doCompare(Object o1, Object o2, @Nullable OrderSourceProvider sourceProvider) {
+	private int doCompare(@Nullable Object o1, @Nullable Object o2, @Nullable OrderSourceProvider sourceProvider) {
 		boolean p1 = (o1 instanceof PriorityOrdered);
 		boolean p2 = (o2 instanceof PriorityOrdered);
 		if (p1 && !p2) {
@@ -92,9 +92,9 @@ public class OrderComparator implements Comparator<Object> {
 	 * @param obj the object to check
 	 * @return the order value, or {@code Ordered.LOWEST_PRECEDENCE} as fallback
 	 */
-	private int getOrder(Object obj, @Nullable OrderSourceProvider sourceProvider) {
+	private int getOrder(@Nullable Object obj, @Nullable OrderSourceProvider sourceProvider) {
 		Integer order = null;
-		if (sourceProvider != null) {
+		if (obj != null && sourceProvider != null) {
 			Object orderSource = sourceProvider.getOrderSource(obj);
 			if (orderSource != null) {
 				if (orderSource.getClass().isArray()) {
@@ -121,9 +121,14 @@ public class OrderComparator implements Comparator<Object> {
 	 * @param obj the object to check
 	 * @return the order value, or {@code Ordered.LOWEST_PRECEDENCE} as fallback
 	 */
-	protected int getOrder(Object obj) {
-		Integer order = findOrder(obj);
-		return (order != null ? order : Ordered.LOWEST_PRECEDENCE);
+	protected int getOrder(@Nullable Object obj) {
+		if (obj != null) {
+			Integer order = findOrder(obj);
+			if (order != null) {
+				return order;
+			}
+		}
+		return Ordered.LOWEST_PRECEDENCE;
 	}
 
 	/**

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -20,34 +20,48 @@ import java.util.Comparator;
 
 import org.junit.Test;
 
-import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.*;
 
 /**
  * Unit tests for the {@link OrderComparator} class.
  *
  * @author Rick Evans
  * @author Stephane Nicoll
+ * @author Juergen Hoeller
  */
 public class OrderComparatorTests {
 
 	private final OrderComparator comparator = new OrderComparator();
 
+
 	@Test
 	public void compareOrderedInstancesBefore() {
-		assertEquals(-1, this.comparator.compare(
-				new StubOrdered(100), new StubOrdered(2000)));
+		assertEquals(-1, this.comparator.compare(new StubOrdered(100), new StubOrdered(2000)));
 	}
 
 	@Test
 	public void compareOrderedInstancesSame() {
-		assertEquals(0, this.comparator.compare(
-				new StubOrdered(100), new StubOrdered(100)));
+		assertEquals(0, this.comparator.compare(new StubOrdered(100), new StubOrdered(100)));
 	}
 
 	@Test
 	public void compareOrderedInstancesAfter() {
-		assertEquals(1, this.comparator.compare(
-				new StubOrdered(982300), new StubOrdered(100)));
+		assertEquals(1, this.comparator.compare(new StubOrdered(982300), new StubOrdered(100)));
+	}
+
+	@Test
+	public void compareOrderedInstancesNullFirst() {
+		assertEquals(1, this.comparator.compare(null, new StubOrdered(100)));
+	}
+
+	@Test
+	public void compareOrderedInstancesNullLast() {
+		assertEquals(-1, this.comparator.compare(new StubOrdered(100), null));
+	}
+
+	@Test
+	public void compareOrderedInstancesDoubleNull() {
+		assertEquals(0, this.comparator.compare(null, null));
 	}
 
 	@Test
@@ -87,6 +101,7 @@ public class OrderComparatorTests {
 	private static final class TestSourceProvider implements OrderComparator.OrderSourceProvider {
 
 		private final Object target;
+
 		private final Object orderSource;
 
 		public TestSourceProvider(Object target, Object orderSource) {
@@ -103,6 +118,7 @@ public class OrderComparatorTests {
 		}
 	}
 
+
 	private static final class StubOrdered implements Ordered {
 
 		private final int order;

spring-core/src/test/java/org/springframework/core/annotation/AnnotationAwareOrderComparatorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -96,6 +96,20 @@ public class AnnotationAwareOrderComparatorTests {
 		assertEquals(B.class, list.get(1));
 	}
 
+	@Test
+	public void sortWithNulls() {
+		List<Object> list = new ArrayList<>();
+		list.add(null);
+		list.add(B.class);
+		list.add(null);
+		list.add(A.class);
+		AnnotationAwareOrderComparator.sort(list);
+		assertEquals(A.class, list.get(0));
+		assertEquals(B.class, list.get(1));
+		assertNull(list.get(2));
+		assertNull(list.get(3));
+	}
+
 
 	@Order(1)
 	private static class A {