DATACMNS-1364 - Store persistent properties in ConcurrentHashMap.

We now use ConcurrentHashMap to store persistent properties of a PersistentEntity and to prevent eviction caused by GC activity. Previously, we used ConcurrentReferenceHashMap defaulting to soft references. Soft references can be cleared at the discretion of the GC in response to memory demand. So a default ConcurrentReferenceHashMap is memory-sensitive and acts like a cache with memory-based eviction rules.

Persistent properties are not subject to be cached but elements of a PersistentEntity and cannot be recovered once cleared.

Original pull request: #304.

Author: mp911de

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

@@ -104,7 +104,7 @@ public BasicPersistentEntity(TypeInformation<T> information, @Nullable Comparato
 		this.constructor = PreferredConstructorDiscoverer.discover(this);
 		this.associations = comparator == null ? new HashSet<>() : new TreeSet<>(new AssociationComparator<>(comparator));
 
-		this.propertyCache = new ConcurrentReferenceHashMap<>();
+		this.propertyCache = new ConcurrentHashMap<>();
 		this.annotationCache = new ConcurrentReferenceHashMap<>();
 		this.propertyAnnotationCache = CollectionUtils.toMultiValueMap(new ConcurrentReferenceHashMap<>());
 		this.propertyAccessorFactory = BeanWrapperPropertyAccessorFactory.INSTANCE;

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

@@ -138,24 +138,27 @@ public void considersComparatorForPropertyOrder() {
 		assertThat(entity.getPersistentProperty("ssn")).isEqualTo(iterator.next());
 	}
 
-	@Test // DATACMNS-186
+	@Test // DATACMNS-18, DATACMNS-1364
 	public void addingAndIdPropertySetsIdPropertyInternally() {
 
 		MutablePersistentEntity<Person, T> entity = createEntity(Person.class);
 		assertThat(entity.getIdProperty()).isNull();
 
+		when(property.getName()).thenReturn("id");
 		when(property.isIdProperty()).thenReturn(true);
 		entity.addPersistentProperty(property);
 		assertThat(entity.getIdProperty()).isEqualTo(property);
 	}
 
-	@Test // DATACMNS-186
+	@Test // DATACMNS-186, DATACMNS-1364
 	public void rejectsIdPropertyIfAlreadySet() {
 
 		MutablePersistentEntity<Person, T> entity = createEntity(Person.class);
 
+		when(property.getName()).thenReturn("id");
 		when(property.isIdProperty()).thenReturn(true);
 		when(anotherProperty.isIdProperty()).thenReturn(true);
+		when(anotherProperty.getName()).thenReturn("another");
 
 		entity.addPersistentProperty(property);
 		exception.expect(MappingException.class);
@@ -429,7 +432,7 @@ static class PersistableEntity implements Persistable<Long> {
 
 		private final Long id = 42L;
 
-		/* 
+		/*
 		 * (non-Javadoc)
 		 * @see org.springframework.data.domain.Persistable#getId()
 		 */
@@ -438,7 +441,7 @@ public Long getId() {
 			return 4711L;
 		}
 
-		/* 
+		/*
 		 * (non-Javadoc)
 		 * @see org.springframework.data.domain.Persistable#isNew()
 		 */