DATAJPA-1622 - Removed @Nullable annotation for return types of Specification.

This allows for easier usage as a fluent API without warnings from the IDE or in the case of Kotlin compiler errors.

Original pull request: #397.

Author: schauder

src/main/java/org/springframework/data/jpa/domain/Specification.java

@@ -34,6 +34,7 @@
  * @author Krzysztof Rzymkowski
  * @author Sebastian Staudt
  * @author Mark Paluch
+ * @author Jens Schauder
  */
 public interface Specification<T> extends Serializable {
 
@@ -62,7 +63,6 @@ static <T> Specification<T> not(@Nullable Specification<T> spec) {
 	 * @return
 	 * @since 2.0
 	 */
-	@Nullable
 	static <T> Specification<T> where(@Nullable Specification<T> spec) {
 		return spec == null ? (root, query, builder) -> null : spec;
 	}
@@ -74,7 +74,7 @@ static <T> Specification<T> where(@Nullable Specification<T> spec) {
 	 * @return The conjunction of the specifications
 	 * @since 2.0
 	 */
-	@Nullable
+
 	default Specification<T> and(@Nullable Specification<T> other) {
 		return composed(this, other, (builder, left, rhs) -> builder.and(left, rhs));
 	}
@@ -86,7 +86,6 @@ default Specification<T> and(@Nullable Specification<T> other) {
 	 * @return The disjunction of the specifications
 	 * @since 2.0
 	 */
-	@Nullable
 	default Specification<T> or(@Nullable Specification<T> other) {
 		return composed(this, other, (builder, left, rhs) -> builder.or(left, rhs));
 	}

src/main/java/org/springframework/data/jpa/domain/SpecificationComposition.java

@@ -29,6 +29,7 @@
  *
  * @author Sebastian Staudt
  * @author Oliver Gierke
+ * @author Jens Schauder
  * @see Specification
  * @since 2.2
  */
@@ -38,7 +39,6 @@ interface Combiner extends Serializable {
 		Predicate combine(CriteriaBuilder builder, @Nullable Predicate lhs, @Nullable Predicate rhs);
 	}
 
-	@Nullable
 	static <T> Specification<T> composed(@Nullable Specification<T> lhs, @Nullable Specification<T> rhs,
 			Combiner combiner) {
 
@@ -55,7 +55,8 @@ static <T> Specification<T> composed(@Nullable Specification<T> lhs, @Nullable S
 		};
 	}
 
-	private static <T> Predicate toPredicate(Specification<T> specification, Root<T> root, CriteriaQuery<?> query,
+	@Nullable
+	private static <T> Predicate toPredicate(@Nullable Specification<T> specification, Root<T> root, CriteriaQuery<?> query,
 			CriteriaBuilder builder) {
 		return specification == null ? null : specification.toPredicate(root, query, builder);
 	}