DATACMNS-1141 - Add missing NonNullApi and Nullable annotations.

Add Nullable annotation to ParsingUtils, Sort.Order and PropertyValueProvider.

Add getRequiredAnnotation(…) to PersistentEntity and PersistentProperty to provide methods returning required, non-null annotations.

src/main/java/org/springframework/data/config/ParsingUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2012 the original author or authors.
+ * Copyright 2011-2017 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.
@@ -30,6 +30,7 @@ import org.w3c.dom.Element;
  * Utility methods for {@link BeanDefinitionParser} implementations.
  * 
  * @author Oliver Gierke
+ * @author Mark Paluch
  */
 public abstract class ParsingUtils {
 
@@ -138,7 +139,7 @@ public abstract class ParsingUtils {
 	 * @param source
 	 * @return
 	 */
-	public static AbstractBeanDefinition getObjectFactoryBeanDefinition(String targetBeanName, Object source) {
+	public static AbstractBeanDefinition getObjectFactoryBeanDefinition(String targetBeanName, @Nullable Object source) {
 
 		Assert.hasText(targetBeanName, "Target bean name must not be null or empty!");