DATAJPA-658 - Polishing.

Moved identifier attribute detection into JpaMetamodel and refactored to Java 8 Stream based lookup. The identifier property calculation is now contained in a Lazy instance so that repeated calls reuse the same outcome.

Original pull request: #146.

src/main/java/org/springframework/data/jpa/mapping/JpaPersistentPropertyImpl.java

@@ -35,9 +35,7 @@ import javax.persistence.OneToOne;
 import javax.persistence.OrderColumn;
 import javax.persistence.Transient;
 import javax.persistence.Version;
-import javax.persistence.metamodel.EntityType;
 import javax.persistence.metamodel.Metamodel;
-import javax.persistence.metamodel.SingularAttribute;
 
 import org.springframework.core.annotation.AnnotationUtils;
 import org.springframework.data.annotation.AccessType.Type;
@@ -48,6 +46,7 @@ import org.springframework.data.mapping.model.AnnotationBasedPersistentProperty;
 import org.springframework.data.mapping.model.Property;
 import org.springframework.data.mapping.model.SimpleTypeHolder;
 import org.springframework.data.util.ClassTypeInformation;
+import org.springframework.data.util.Lazy;
 import org.springframework.data.util.TypeInformation;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
@@ -97,7 +96,8 @@ class JpaPersistentPropertyImpl extends AnnotationBasedPersistentProperty<JpaPer
 	private final @Nullable TypeInformation<?> associationTargetType;
 	private final boolean updateable;
 	private final JpaMetamodel metamodel;
-	private final EntityType<?> entityType;
+
+	private final Lazy<Boolean> isIdProperty;
 
 	/**
 	 * Creates a new {@link JpaPersistentPropertyImpl}
@@ -114,33 +114,13 @@ class JpaPersistentPropertyImpl extends AnnotationBasedPersistentProperty<JpaPer
 
 		Assert.notNull(metamodel, "Metamodel must not be null!");
 
-		this.entityType = tryResolveEntityType(metamodel, getOwner().getType());
 		this.usePropertyAccess = detectPropertyAccess();
 		this.associationTargetType = detectAssociationTargetType();
 		this.updateable = detectUpdatability();
 		this.metamodel = new JpaMetamodel(metamodel);
-	}
 
-	/**
-	 * Return the {@link EntityType} for the given Entity {@link Class} or null if given {@code type} is not a mapped
-	 * entity.
-	 * 
-	 * @param metamodel
-	 * @param type
-	 * @return
-	 */
-	private EntityType<?> tryResolveEntityType(Metamodel metamodel, Class<?> type) {
-
-		EntityType<?> ownerEntityType = null;
-
-		for (EntityType<?> entityType : metamodel.getEntities()) {
-			if (entityType.getJavaType().equals(type)) {
-				ownerEntityType = entityType;
-				break;
-			}
-		}
-
-		return ownerEntityType;
+		this.isIdProperty = Lazy.of(() -> ID_ANNOTATIONS.stream().anyMatch(it -> isAnnotationPresent(it)) //
+				|| this.metamodel.isSingleIdAttribute(getOwner().getType(), getName(), getType()));
 	}
 
 	/*
@@ -168,27 +148,7 @@ class JpaPersistentPropertyImpl extends AnnotationBasedPersistentProperty<JpaPer
 	 */
 	@Override
 	public boolean isIdProperty() {
-
-		boolean isId ID_ANNOTATIONS.stream().anyMatch(it -> isAnnotationPresent(it));
-
-		if (isId) {
-			return true;
-		}
-
-		if (isIdPropertyCandidateAccordingToMetaModel()) {
-
-			SingularAttribute<?, ?> idAttribute = entityType.getId(getType());
-			if (idAttribute.getName().equals(getName())) {
-				return true;
-			}
-		}
-
-		return false;
-	}
-
-	private boolean isIdPropertyCandidateAccordingToMetaModel() {
-		return entityType != null && entityType.hasSingleIdAttribute()
-				&& entityType.getIdType().getJavaType().equals(getType());
+		return isIdProperty.get();
 	}
 
 	/*

src/main/java/org/springframework/data/jpa/util/JpaMetamodel.java

@@ -21,8 +21,10 @@ import java.util.HashSet;
 import java.util.Optional;
 import java.util.Set;
 
+import javax.persistence.metamodel.EntityType;
 import javax.persistence.metamodel.ManagedType;
 import javax.persistence.metamodel.Metamodel;
+import javax.persistence.metamodel.SingularAttribute;
 
 import org.springframework.util.Assert;
 
@@ -63,6 +65,25 @@ public class JpaMetamodel {
 		return getManagedTypes().contains(type);
 	}
 
+	/**
+	 * Returns whether the attribute of given name and type is the single identifier attribute of the given entity.
+	 * 
+	 * @param entity must not be {@literal null}.
+	 * @param name must not be {@literal null}.
+	 * @param attributeType must not be {@literal null}.
+	 * @return
+	 */
+	public boolean isSingleIdAttribute(Class<?> entity, String name, Class<?> attributeType) {
+
+		return metamodel.getEntities().stream() //
+				.filter(it -> it.getJavaType().equals(entity)) //
+				.findFirst() //
+				.flatMap(it -> getSingularIdAttribute(it)) //
+				.filter(it -> it.getJavaType().equals(attributeType)) //
+				.map(it -> it.getName().equals(name)) //
+				.orElse(false);
+	}
+
 	/**
 	 * Returns all types managed by the backing {@link Metamodel}. Skips {@link ManagedType} instances that return
 	 * {@literal null} for calls to {@link ManagedType#getJavaType()}.
@@ -91,4 +112,22 @@ public class JpaMetamodel {
 
 		return this.managedTypes.get();
 	}
+
+	/**
+	 * Returns the {@link SingularAttribute} representing the identifier of the given {@link EntityType} if it contains a
+	 * singular one.
+	 * 
+	 * @param entityType must not be {@literal null}.
+	 * @return
+	 */
+	private static Optional<? extends SingularAttribute<?, ?>> getSingularIdAttribute(EntityType<?> entityType) {
+
+		if (!entityType.hasSingleIdAttribute()) {
+			return Optional.empty();
+		}
+
+		return entityType.getSingularAttributes().stream() //
+				.filter(SingularAttribute::isId) //
+				.findFirst();
+	}
 }