DATACMNS-1325 - Added dedicated identifier accessor for Persistable entities.

BasicPersistentEntity now returns a dedicated IdentifierAccessor that uses Persistable.getId() in case the entity implements Persistable.

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

@@ -34,6 +34,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.data.annotation.TypeAlias;
+import org.springframework.data.domain.Persistable;
 import org.springframework.data.mapping.Association;
 import org.springframework.data.mapping.AssociationHandler;
 import org.springframework.data.mapping.IdentifierAccessor;
@@ -435,6 +436,10 @@ public class BasicPersistentEntity<T, P extends PersistentProperty<P>> implement
 		Assert.notNull(bean, "Target bean must not be null!");
 		assertBeanType(bean);
 
+		if (Persistable.class.isAssignableFrom(getType())) {
+			return new PersistableIdentifierAccessor((Persistable<?>) bean);
+		}
+
 		return hasIdProperty() ? new IdPropertyIdentifierAccessor(this, bean) : NullReturningIdentifierAccessor.INSTANCE;
 	}
 

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

@@ -0,0 +1,32 @@
+package org.springframework.data.mapping.model;
+
+import org.springframework.data.domain.Persistable;
+import org.springframework.data.mapping.IdentifierAccessor;
+
+/**
+ * {@link IdentifierAccessor} that invokes {@link Persistable#getId()}.
+ * 
+ * @author Oliver Gierke
+ */
+class PersistableIdentifierAccessor implements IdentifierAccessor {
+
+	private final Persistable<?> target;
+
+	/**
+	 * Creates a new {@link PersistableIdentifierAccessor} for the given target.
+	 * 
+	 * @param target must not be {@literal null}.
+	 */
+	public PersistableIdentifierAccessor(Persistable<?> target) {
+		this.target = target;
+	}
+
+	/* 
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mapping.IdentifierAccessor#getIdentifier()
+	 */
+	@Override
+	public Object getIdentifier() {
+		return target.getId();
+	}
+}

src/test/java/org/springframework/data/mapping/model/BasicPersistentEntityUnitTests.java

@@ -40,6 +40,7 @@ import org.springframework.data.annotation.CreatedBy;
 import org.springframework.data.annotation.CreatedDate;
 import org.springframework.data.annotation.LastModifiedBy;
 import org.springframework.data.annotation.TypeAlias;
+import org.springframework.data.domain.Persistable;
 import org.springframework.data.mapping.Association;
 import org.springframework.data.mapping.PersistentEntity;
 import org.springframework.data.mapping.PersistentEntitySpec;
@@ -260,6 +261,14 @@ public class BasicPersistentEntityUnitTests<T extends PersistentProperty<T>> {
 		});
 	}
 
+	@Test // DATACMNS-1325
+	public void supportsPersistableViaIdentifierAccessor() {
+
+		PersistentEntity<PersistableEntity, T> entity = createEntity(PersistableEntity.class);
+
+		assertThat(entity.getIdentifierAccessor(new PersistableEntity()).getIdentifier(), is((Object) 4711L));
+	}
+
 	private <S> BasicPersistentEntity<S, T> createEntity(Class<S> type) {
 		return createEntity(type, null);
 	}
@@ -299,4 +308,29 @@ public class BasicPersistentEntityUnitTests<T extends PersistentProperty<T>> {
 	static class AliasEntityUsingComposedAnnotation {}
 
 	static class Subtype extends Entity {}
+
+	// DATACMNS-1325
+
+	static class PersistableEntity implements Persistable<Long> {
+
+		private final Long id = 42L;
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.domain.Persistable#getId()
+		 */
+		@Override
+		public Long getId() {
+			return 4711L;
+		}
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.domain.Persistable#isNew()
+		 */
+		@Override
+		public boolean isNew() {
+			return false;
+		}
+	}
 }