DATAJPA-83 - Added getOne(ID id) to JpaRepository.

Added a getOne(ID id) method to both JpaRepository as well as SimpleJpaRepository to be able to obtain references to entities (as implemented by EntityManager.getReference(…)).

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

@@ -18,6 +18,8 @@ package org.springframework.data.jpa.repository;
 import java.io.Serializable;
 import java.util.List;
 
+import javax.persistence.EntityManager;
+
 import org.springframework.data.domain.Sort;
 import org.springframework.data.repository.NoRepositoryBean;
 import org.springframework.data.repository.PagingAndSortingRepository;
@@ -79,4 +81,13 @@ public interface JpaRepository<T, ID extends Serializable> extends PagingAndSort
 	 * Deletes all entites in a batch call.
 	 */
 	void deleteAllInBatch();
+
+	/**
+	 * Returns a reference to the entity with the given identifier.
+	 * 
+	 * @param id must not be {@literal null}.
+	 * @return a reference to the entity with the given identifier.
+	 * @see EntityManager#getReference(Class, Object)
+	 */
+	T getOne(ID id);
 }

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

@@ -212,6 +212,17 @@ public class SimpleJpaRepository<T, ID extends Serializable> implements JpaRepos
 		return type == null ? em.find(domainType, id) : em.find(domainType, id, type);
 	}
 
+	/* 
+	 * (non-Javadoc)
+	 * @see org.springframework.data.jpa.repository.JpaRepository#getOne(java.io.Serializable)
+	 */
+	@Override
+	public T getOne(ID id) {
+
+		Assert.notNull(id, "The given id must not be null!");
+		return em.getReference(getDomainClass(), id);
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.repository.CrudRepository#exists(java.io.Serializable)

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

@@ -1093,6 +1093,18 @@ public class UserRepositoryTests {
 		assertThat(lastname, hasItem("Dave"));
 	}
 
+	/**
+	 * @see DATAJPA-83
+	 */
+	@Test
+	public void looksUpEntityReference() {
+
+		flushTestUsers();
+
+		User result = repository.getOne(firstUser.getId());
+		assertThat(result, is(firstUser));
+	}
+
 	private Page<User> executeSpecWithSort(Sort sort) {
 
 		flushTestUsers();