Introduce JpaRepository.getReferenceById.

Introduce a repository method that makes it clear the return value is a reference. Deprecate the previous methods.

Closes #2232
Original pull request #2398

Author: gregturn

src/main/java/org/springframework/data/jpa/repository/JpaRepository.java

@@ -33,6 +33,7 @@
  * @author Mark Paluch
  * @author Sander Krabbenborg
  * @author Jesse Wouters
+ * @author Greg Turnquist
  */
 @NoRepositoryBean
 public interface JpaRepository<T, ID> extends PagingAndSortingRepository<T, ID>, QueryByExampleExecutor<T> {
@@ -96,7 +97,9 @@ public interface JpaRepository<T, ID> extends PagingAndSortingRepository<T, ID>,
 	 * @deprecated Use {@link #deleteAllInBatch(Iterable)} instead.
 	 */
 	@Deprecated
-	default void deleteInBatch(Iterable<T> entities){deleteAllInBatch(entities);}
+	default void deleteInBatch(Iterable<T> entities) {
+		deleteAllInBatch(entities);
+	}
 
 	/**
 	 * Deletes the given entities in a batch which means it will create a single query. This kind of operation leaves JPAs
@@ -108,7 +111,6 @@ public interface JpaRepository<T, ID> extends PagingAndSortingRepository<T, ID>,
 	 */
 	void deleteAllInBatch(Iterable<T> entities);
 
-
 	/**
 	 * Deletes the entities identified by the given ids using a single query. This kind of operation leaves JPAs first
 	 * level cache and the database out of sync. Consider flushing the {@link EntityManager} before calling this method.
@@ -132,7 +134,7 @@ public interface JpaRepository<T, ID> extends PagingAndSortingRepository<T, ID>,
 	 * @param id must not be {@literal null}.
 	 * @return a reference to the entity with the given identifier.
 	 * @see EntityManager#getReference(Class, Object) for details on when an exception is thrown.
-	 * @deprecated use {@link JpaRepository#getById(ID)} instead.
+	 * @deprecated use {@link JpaRepository#getReferenceById(ID)} instead.
 	 */
 	@Deprecated
 	T getOne(ID id);
@@ -146,10 +148,25 @@ public interface JpaRepository<T, ID> extends PagingAndSortingRepository<T, ID>,
 	 * @param id must not be {@literal null}.
 	 * @return a reference to the entity with the given identifier.
 	 * @see EntityManager#getReference(Class, Object) for details on when an exception is thrown.
+	 * @deprecated use {@link JpaRepository#getReferenceById(ID)} instead.
 	 * @since 2.5
 	 */
+	@Deprecated
 	T getById(ID id);
 
+	/**
+	 * Returns a reference to the entity with the given identifier. Depending on how the JPA persistence provider is
+	 * implemented this is very likely to always return an instance and throw an
+	 * {@link javax.persistence.EntityNotFoundException} on first access. Some of them will reject invalid identifiers
+	 * immediately.
+	 *
+	 * @param id must not be {@literal null}.
+	 * @return a reference to the entity with the given identifier.
+	 * @see EntityManager#getReference(Class, Object) for details on when an exception is thrown.
+	 * @since 2.7
+	 */
+	T getReferenceById(ID id);
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.repository.query.QueryByExampleExecutor#findAll(org.springframework.data.domain.Example)

src/main/java/org/springframework/data/jpa/repository/support/SimpleJpaRepository.java

@@ -331,26 +331,34 @@ protected QueryHints getQueryHints() {
 	@Deprecated
 	@Override
 	public T getOne(ID id) {
-
-		Assert.notNull(id, ID_MUST_NOT_BE_NULL);
-		return em.getReference(getDomainClass(), id);
+		return getReferenceById(id);
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.jpa.repository.JpaRepository#getById(java.io.Serializable)
 	 */
+	@Deprecated
 	@Override
 	public T getById(ID id) {
+		return getReferenceById(id);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.jpa.repository.JpaRepository#getReferenceById(java.io.Serializable)
+	 */
+	@Override
+	public T getReferenceById(ID id) {
 
 		Assert.notNull(id, ID_MUST_NOT_BE_NULL);
 		return em.getReference(getDomainClass(), id);
 	}
 
 	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.repository.CrudRepository#existsById(java.io.Serializable)
-	 */
+	* (non-Javadoc)
+	* @see org.springframework.data.repository.CrudRepository#existsById(java.io.Serializable)
+	*/
 	@Override
 	public boolean existsById(ID id) {
 

src/test/java/org/springframework/data/jpa/repository/AbstractPersistableIntegrationTests.java

@@ -21,7 +21,6 @@
 
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
-
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.data.jpa.domain.AbstractPersistable;
 import org.springframework.data.jpa.domain.sample.CustomAbstractPersistable;
@@ -37,6 +36,7 @@
  * @author Oliver Gierke
  * @author Jens Schauder
  * @author Jesse Wouters
+ * @author Greg Turnquist
  */
 @Transactional
 @ExtendWith(SpringExtension.class)
@@ -79,4 +79,16 @@ void equalsWorksForProxiedEntitiesUsingGetById() {
 
 		assertThat(proxy).isEqualTo(proxy);
 	}
+
+	@Test // gh-1697
+	void equalsWorksForProxiedEntitiesUsingGetReferenceById() {
+
+		CustomAbstractPersistable entity = repository.saveAndFlush(new CustomAbstractPersistable());
+
+		em.clear();
+
+		CustomAbstractPersistable proxy = repository.getReferenceById(entity.getId());
+
+		assertThat(proxy).isEqualTo(proxy);
+	}
 }

src/test/java/org/springframework/data/jpa/repository/UserRepositoryTests.java

@@ -1011,7 +1011,16 @@ void looksUpEntityReferenceUsingGetById() {
 		assertThat(result).isEqualTo(firstUser);
 	}
 
-	@Test // DATAJPA-415
+    @Test // gh-1697
+    void looksUpEntityReferenceUsingGetReferenceById() {
+
+        flushTestUsers();
+
+        User result = repository.getReferenceById(firstUser.getId());
+        assertThat(result).isEqualTo(firstUser);
+    }
+
+    @Test // DATAJPA-415
 	void invokesQueryWithVarargsParametersCorrectly() {
 
 		flushTestUsers();