Polishing.

Remove JPA 2.1 guards as we require JPA 3.x. Refine API to reduce nullability.

Original pull request: #3684
See #3682

Author: mp911de

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/query/AbstractJpaQuery.java

@@ -256,7 +256,7 @@ private Query applyEntityGraphConfiguration(Query query, JpaQueryMethod method)
 		JpaEntityGraph entityGraph = method.getEntityGraph();
 
 		if (entityGraph != null) {
-			QueryHints hints = Jpa21Utils.getFetchGraphHint(em, method.getEntityGraph(),
+			QueryHints hints = Jpa21Utils.getFetchGraphHint(em, entityGraph,
 					getQueryMethod().getEntityInformation().getJavaType());
 
 			hints.forEach(query::setHint);

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/query/Jpa21Utils.java

@@ -15,24 +15,21 @@
  */
 package org.springframework.data.jpa.repository.query;
 
-import java.lang.reflect.Method;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-
 import jakarta.persistence.AttributeNode;
 import jakarta.persistence.EntityGraph;
 import jakarta.persistence.EntityManager;
 import jakarta.persistence.Query;
 import jakarta.persistence.Subgraph;
 
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
 import org.springframework.data.jpa.repository.support.MutableQueryHints;
 import org.springframework.data.jpa.repository.support.QueryHints;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
-import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
-import org.springframework.util.ReflectionUtils;
 import org.springframework.util.StringUtils;
 
 /**
@@ -48,38 +45,16 @@
  */
 public class Jpa21Utils {
 
-	private static final @Nullable Method GET_ENTITY_GRAPH_METHOD;
-	private static final boolean JPA21_AVAILABLE = ClassUtils.isPresent("jakarta.persistence.NamedEntityGraph",
-			Jpa21Utils.class.getClassLoader());
-
-	static {
-
-		if (JPA21_AVAILABLE) {
-			GET_ENTITY_GRAPH_METHOD = ReflectionUtils.findMethod(EntityManager.class, "getEntityGraph", String.class);
-		} else {
-			GET_ENTITY_GRAPH_METHOD = null;
-		}
-	}
-
 	private Jpa21Utils() {
 		// prevent instantiation
 	}
 
-	public static QueryHints getFetchGraphHint(EntityManager em, @Nullable JpaEntityGraph entityGraph,
-			Class<?> entityType) {
+	public static QueryHints getFetchGraphHint(EntityManager em, JpaEntityGraph entityGraph, Class<?> entityType) {
 
 		MutableQueryHints result = new MutableQueryHints();
 
-		if (entityGraph == null) {
-			return result;
-		}
-
 		EntityGraph<?> graph = tryGetFetchGraph(em, entityGraph, entityType);
 
-		if (graph == null) {
-			return result;
-		}
-
 		result.add(entityGraph.getType().getKey(), graph);
 		return result;
 	}
@@ -94,24 +69,21 @@ public static QueryHints getFetchGraphHint(EntityManager em, @Nullable JpaEntity
 	 * @param entityType must not be {@literal null}.
 	 * @return the {@link EntityGraph} described by the given {@code entityGraph}.
 	 */
-	@Nullable
 	private static EntityGraph<?> tryGetFetchGraph(EntityManager em, JpaEntityGraph jpaEntityGraph, Class<?> entityType) {
 
 		Assert.notNull(em, "EntityManager must not be null");
 		Assert.notNull(jpaEntityGraph, "EntityGraph must not be null");
 		Assert.notNull(entityType, "EntityType must not be null");
 
-		Assert.isTrue(JPA21_AVAILABLE, "The EntityGraph-Feature requires at least a JPA 2.1 persistence provider");
-		Assert.isTrue(GET_ENTITY_GRAPH_METHOD != null,
-				"It seems that you have the JPA 2.1 API but a JPA 2.0 implementation on the classpath");
+		if (StringUtils.hasText(jpaEntityGraph.getName())) {
 
-		try {
-			// first check whether an entityGraph with that name is already registered.
-			return em.getEntityGraph(jpaEntityGraph.getName());
-		} catch (Exception ex) {
-			// try to create and dynamically register the entityGraph
-			return createDynamicEntityGraph(em, jpaEntityGraph, entityType);
+			try {
+				// check whether an entityGraph with that name is already registered.
+				return em.getEntityGraph(jpaEntityGraph.getName());
+			} catch (Exception ignore) {}
 		}
+
+		return createDynamicEntityGraph(em, jpaEntityGraph, entityType);
 	}
 
 	/**

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/support/DefaultQueryHints.java

@@ -15,11 +15,11 @@
  */
 package org.springframework.data.jpa.repository.support;
 
+import jakarta.persistence.EntityManager;
+
 import java.util.Optional;
 import java.util.function.BiConsumer;
 
-import jakarta.persistence.EntityManager;
-
 import org.springframework.data.jpa.repository.EntityGraph;
 import org.springframework.data.jpa.repository.query.Jpa21Utils;
 import org.springframework.data.jpa.repository.query.JpaEntityGraph;
@@ -99,7 +99,7 @@ private QueryHints getFetchGraphs() {
 		return Optionals
 				.mapIfAllPresent(entityManager, metadata.getEntityGraph(),
 						(em, graph) -> Jpa21Utils.getFetchGraphHint(em, getEntityGraph(graph), information.getJavaType()))
-				.orElse(new MutableQueryHints());
+				.orElseGet(MutableQueryHints::new);
 	}
 
 	private JpaEntityGraph getEntityGraph(EntityGraph entityGraph) {

src/main/antora/modules/ROOT/pages/jpa/query-methods.adoc

@@ -824,7 +824,7 @@ public interface GroupRepository extends CrudRepository<GroupInfo, String> {
 
 It is also possible to define ad hoc entity graphs by using `@EntityGraph`. The provided `attributePaths` are translated into the according `EntityGraph` without needing to explicitly add `@NamedEntityGraph` to your domain types, as shown in the following example:
 
-.Using AD-HOC entity graph definition on an repository query method.
+.Using ad-hoc entity graph definitions on a repository query method
 ====
 [source, java]
 ----