[BAEL-4056] Guide to MultipleBagFetchException (#10294)

* Adds Domain Models * Adds Integration Tests
2020-12-01 15:22:46 +08:00
parent 06bebff4cb
commit cd6f187e0a
10 changed files with 572 additions and 0 deletions
@@ -0,0 +1,124 @@
+package com.baeldung.jpa.multiplebagfetchexception;
+
+import org.hibernate.jpa.QueryHints;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.Persistence;
+import javax.persistence.Query;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class MultipleBagFetchExceptionIntegrationTest {
+
+    private static EntityManager entityManager;
+
+    @BeforeAll
+    public static void setup() {
+        EntityManagerFactory factory = Persistence.createEntityManagerFactory("jpa-h2-multiple-bag-fetch-exception");
+        entityManager = factory.createEntityManager();
+        populateH2DB();
+    }
+
+    @Test
+    public void whenFetchingMoreThanOneBag_thenThrowAnException() {
+        IllegalArgumentException exception =
+          assertThrows(IllegalArgumentException.class, () -> {
+            String jpql = "SELECT dummy FROM DummyEntity dummy "
+              + "JOIN FETCH dummy.collection1 "
+              + "JOIN FETCH dummy.collection2 ";
+
+            entityManager.createQuery(jpql);
+        });
+
+        final String expectedMessagePart = "MultipleBagFetchException";
+        final String actualMessage = exception.getMessage();
+
+        assertTrue(actualMessage.contains(expectedMessagePart));
+    }
+
+    @Test
+    public void whenFetchingOneBagAndSet_thenRetrieveSuccess() {
+        String jpql = "SELECT DISTINCT album FROM Album album "
+          + "LEFT JOIN FETCH album.songs "
+          + "LEFT JOIN FETCH album.followers "
+          + "WHERE album.id = 1";
+
+        Query query = entityManager.createQuery(jpql)
+          .setHint(QueryHints.HINT_PASS_DISTINCT_THROUGH, false);
+
+        assertEquals(1, query.getResultList().size());
+    }
+
+    @Test
+    public void whenUsingMultipleQueries_thenRetrieveSuccess() {
+        String jpql = "SELECT DISTINCT artist FROM Artist artist "
+          + "LEFT JOIN FETCH artist.songs ";
+
+        List<Artist> artists = entityManager.createQuery(jpql, Artist.class)
+          .setHint(QueryHints.HINT_PASS_DISTINCT_THROUGH, false)
+          .getResultList();
+
+        jpql = "SELECT DISTINCT artist FROM Artist artist "
+          + "LEFT JOIN FETCH artist.offers "
+          + "WHERE artist IN :artists ";
+
+        artists = entityManager.createQuery(jpql, Artist.class)
+          .setParameter("artists", artists)
+          .setHint(QueryHints.HINT_PASS_DISTINCT_THROUGH, false)
+          .getResultList();
+
+        assertEquals(2, artists.size());
+    }
+
+    @Test
+    public void whenFetchingOneBagAndOneList_thenRetrieveSuccess() {
+        String jpql = "SELECT DISTINCT user FROM User user "
+          + "LEFT JOIN FETCH user.playlists "
+          + "LEFT JOIN FETCH user.favoriteSongs ";
+
+        List<User> users = entityManager.createQuery(jpql, User.class)
+          .setHint(QueryHints.HINT_PASS_DISTINCT_THROUGH, false)
+          .getResultList();
+
+        assertEquals(3, users.size());
+    }
+
+    private static void populateH2DB() {
+        entityManager.getTransaction().begin();
+
+        Album album = new Album("album-name");
+        Artist artist1 = new Artist("artist-name-1");
+        Artist artist2 = new Artist("artist-name-2");
+        artist2.createOffer("offer-name-1");
+        artist2.createOffer("offer-name-2");
+        entityManager.persist(album);
+        entityManager.persist(artist1);
+        entityManager.persist(artist2);
+
+        Song song1 = new Song("song-name-1", artist2);
+        song1.assignToAlbum(album);
+        entityManager.persist(song1);
+
+        User user1 = new User("user-name-1");
+        user1.followAlbum(album);
+        entityManager.persist(user1);
+
+        User user2 = new User("user-name-2");
+        user2.followAlbum(album);
+        entityManager.persist(user2);
+
+        User user3 = new User("user-name-3");
+        user3.createPlaylist("playlist-name");
+        user3.addSongToFavorites(song1);
+        entityManager.persist(user3);
+
+        entityManager.getTransaction().commit();
+    }
+
+}