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/mapping/PersistentEntity.java

@@ -249,6 +249,26 @@ public interface PersistentEntity<T, P extends PersistentProperty<P>> extends It
 	@Nullable
 	<A extends Annotation> A findAnnotation(Class<A> annotationType);
 
+	/**
+	 * Returns the required annotation of the given type on the {@link PersistentEntity}.
+	 *
+	 * @param annotationType must not be {@literal null}.
+	 * @return the annotation.
+	 * @throws IllegalStateException if the required {@code annotationType} is not found.
+	 * @since 2.0
+	 */
+	default <A extends Annotation> A getRequiredAnnotation(Class<A> annotationType) throws IllegalStateException {
+
+		A annotation = findAnnotation(annotationType);
+
+		if (annotation != null) {
+			return annotation;
+		}
+
+		throw new IllegalStateException(
+				String.format("Required annotation %s not found for %s!", annotationType, getType()));
+	}
+
 	/**
 	 * Checks whether the annotation of the given type is present on the {@link PersistentEntity}.
 	 *

src/main/java/org/springframework/data/mapping/PersistentProperty.java

@@ -269,6 +269,27 @@ public interface PersistentProperty<P extends PersistentProperty<P>> {
 	@Nullable
 	<A extends Annotation> A findAnnotation(Class<A> annotationType);
 
+	/**
+	 * Looks up the annotation of the given type on the {@link PersistentProperty}. Will inspect accessors and the
+	 * potentially backing field and traverse accessor methods to potentially available super types.
+	 *
+	 * @param annotationType the annotation to look up, must not be {@literal null}.
+	 * @return the annotation of the given type.
+	 * @throws IllegalStateException if the required {@code annotationType} is not found.
+	 * @since 2.0
+	 */
+	default <A extends Annotation> A getRequiredAnnotation(Class<A> annotationType) throws IllegalStateException {
+
+		A annotation = findAnnotation(annotationType);
+
+		if (annotation != null) {
+			return annotation;
+		}
+
+		throw new IllegalStateException(
+				String.format("Required annotation %s not found for %s!", annotationType, getName()));
+	}
+
 	/**
 	 * Looks up the annotation of the given type on the property and the owning type if no annotation can be found on it.
 	 * Useful to lookup annotations that can be configured on the type but overridden on an individual property.

src/main/java/org/springframework/data/mapping/model/PropertyValueProvider.java

@@ -16,11 +16,13 @@
 package org.springframework.data.mapping.model;
 
 import org.springframework.data.mapping.PersistentProperty;
+import org.springframework.lang.Nullable;
 
 /**
  * SPI for components to provide values for as {@link PersistentProperty}.
  *
  * @author Oliver Gierke
+ * @author Mark Paluch
  */
 public interface PropertyValueProvider<P extends PersistentProperty<P>> {
 
@@ -30,5 +32,6 @@ public interface PropertyValueProvider<P extends PersistentProperty<P>> {
 	 * @param property will never be {@literal null}.
 	 * @return
 	 */
+	@Nullable
 	<T> T getPropertyValue(P property);
 }