[ogm/hiking] Fix database clearing error by executing removal in proper order

Author: emmanuelbernard

hibernate-ogm/hiking-demo/src/main/java/org/hibernate/ogm/hiking/rest/AdminResource.java

@@ -49,7 +49,7 @@ public AdminResource() {
 	@Path("/populate")
 	public void populate() throws Exception {
 		clearDatabase(businessEm);
-		clearDatabase(hikeEm);
+		clearHikeAndTrips(hikeEm);
 
 		Trip corsica = new Trip();
 		corsica.name = "Corsica from north to south";
@@ -99,6 +99,19 @@ public void populate() throws Exception {
 		hikeEm.persist( semiMarathon );
 	}
 
+	private void clearHikeAndTrips(EntityManager em) {
+		List<?> all = em.createQuery( "from Hike" ).getResultList();
+		for ( Hike object : (List<Hike>) all ) {
+			object.recommendedTrip = null;
+			em.remove( object );
+		}
+
+		all = em.createQuery( "from Trip" ).getResultList();
+		for ( Object object : all ) {
+			em.remove( object );
+		}
+	}
+
 	private void clearDatabase(EntityManager em) {
 		List<Object> all = em.createQuery( "from java.lang.Object" ).getResultList();
 		for ( Object object : all ) {

hibernate-ogm/hiking-demo/src/test/java/org/hibernate/ogm/hiking/HikeTest.java

@@ -1,9 +1,12 @@
 package org.hibernate.ogm.hiking;
 
+import java.util.List;
+
 import static org.fest.assertions.Assertions.assertThat;
 
 import javax.persistence.EntityManager;
 import javax.persistence.EntityManagerFactory;
+import javax.persistence.EntityTransaction;
 import javax.persistence.Persistence;
 
 import org.hibernate.ogm.hiking.model.Hike;
@@ -107,4 +110,40 @@ public void validationTest() {
 		entityManager.getTransaction().commit();
 
 	}
+
+	@Test
+	public void testClearDatabase() {
+		EntityTransaction transaction = entityManager.getTransaction();
+		transaction.begin();
+
+		Hike hike = new Hike( "San Francisco", "Oakland" );
+		Trip trip = new Trip();
+		trip.name = "Nappa Valley Unit Test";
+
+		hike.recommendedTrip = trip;
+		trip.availableHikes.add( hike );
+
+		entityManager.persist( trip );
+		entityManager.persist( hike );
+
+		transaction.commit();
+
+		entityManager.clear();
+
+		transaction = entityManager.getTransaction();
+		transaction.begin();
+
+		List<?> all = entityManager.createQuery( "from Hike" ).getResultList();
+		for ( Hike object : (List<Hike>) all ) {
+			object.recommendedTrip = null;
+			entityManager.remove( object );
+		}
+
+		all = entityManager.createQuery( "from Trip" ).getResultList();
+		for ( Object object : all ) {
+			entityManager.remove( object );
+		}
+
+		transaction.commit();
+	}
 }