Add DistinctListTransformer to Hibernate Types 6 #517

hibernate-types-60/src/main/java/com/vladmihalcea/hibernate/query/DistinctListTransformer.java

@@ -0,0 +1,32 @@
+package com.vladmihalcea.hibernate.query;
+
+import org.hibernate.query.ResultListTransformer;
+import org.hibernate.transform.ResultTransformer;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * The {@link DistinctListTransformer} removes duplicates from the {@link List}
+ * of elements that were transformed by the {@link org.hibernate.query.TupleTransformer}.
+ * <p>
+ * This is similar to the {@code DistinctResultTransformer} that was available in Hibernate 5.
+ *
+ * @author Vlad Mihalcea
+ * @since 2.21.0
+ */
+public class DistinctListTransformer<T> implements ResultListTransformer<T> {
+
+    public static final DistinctListTransformer INSTANCE = new DistinctListTransformer();
+
+    /**
+     * Deduplicates the provided List.
+     *
+     * @param collection collections to be deduplicated
+     * @return deduplicated List
+     */
+    @Override
+    public List<T> transformList(List collection) {
+        return (List<T>) collection.stream().distinct().collect(Collectors.toList());
+    }
+}

hibernate-types-60/src/test/java/com/vladmihalcea/hibernate/query/DistinctListTransformerTest.java

@@ -0,0 +1,362 @@
+package com.vladmihalcea.hibernate.query;
+
+import com.vladmihalcea.hibernate.util.AbstractTest;
+import jakarta.persistence.*;
+import org.hibernate.query.TupleTransformer;
+import org.junit.Test;
+
+import java.time.LocalDateTime;
+import java.util.*;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * @author Vlad Mihalcea
+ */
+@SuppressWarnings("unchecked")
+public class DistinctListTransformerTest extends AbstractTest {
+
+    @Override
+    protected Class<?>[] entities() {
+        return new Class<?>[] {
+            Post.class,
+            PostComment.class
+        };
+    }
+
+    @Override
+    public void afterInit() {
+        doInJPA(entityManager -> {
+            entityManager.persist(
+                new Post()
+                    .setId(1L)
+                    .setTitle("High-Performance Java Persistence")
+                    .setCreatedBy("Vlad Mihalcea")
+                    .setCreatedOn(
+                        LocalDateTime.of(2016, 11, 2, 12, 0, 0)
+                    )
+                    .setUpdatedBy("Vlad Mihalcea")
+                    .setUpdatedOn(
+                        LocalDateTime.now()
+                    )
+                    .addComment(
+                        new PostComment()
+                            .setId(1L)
+                            .setReview("Best book on JPA and Hibernate!")
+                    )
+                    .addComment(
+                        new PostComment()
+                            .setId(2L)
+                            .setReview("A must-read for every Java developer!")
+                    )
+            );
+
+
+            entityManager.persist(
+                new Post()
+                    .setId(2L)
+                    .setTitle("Hypersistence Optimizer")
+                    .setCreatedBy("Vlad Mihalcea")
+                    .setCreatedOn(
+                        LocalDateTime.of(2019, 3, 19, 12, 0, 0)
+                    )
+                    .setUpdatedBy("Vlad Mihalcea")
+                    .setUpdatedOn(
+                        LocalDateTime.now()
+                    )
+                    .addComment(
+                        new PostComment()
+                            .setId(3L)
+                            .setReview("It's like pair programming with Vlad!")
+                    )
+            );
+        });
+    }
+
+    @Test
+    public void testParentChildDTOProjectionNativeQueryTupleTransformer() {
+        doInJPA( entityManager -> {
+            List<PostDTO> postDTOs = entityManager.createNativeQuery(
+                "SELECT p.id AS p_id, " +
+                "       p.title AS p_title, " +
+                "       pc.id AS pc_id, " +
+                "       pc.review AS pc_review " +
+                "FROM post p " +
+                "JOIN post_comment pc ON p.id = pc.post_id " +
+                "ORDER BY pc.id")
+            .unwrap(org.hibernate.query.Query.class)
+            .setTupleTransformer(new PostDTOTupleTransformer())
+            .setResultListTransformer(DistinctListTransformer.INSTANCE)
+            .getResultList();
+
+            assertEquals(2, postDTOs.size());
+            assertEquals(2, postDTOs.get(0).getComments().size());
+            assertEquals(1, postDTOs.get(1).getComments().size());
+
+            PostDTO post1DTO = postDTOs.get(0);
+
+            assertEquals(1L, post1DTO.getId().longValue());
+            assertEquals(2, post1DTO.getComments().size());
+            assertEquals(1L, post1DTO.getComments().get(0).getId().longValue());
+            assertEquals(2L, post1DTO.getComments().get(1).getId().longValue());
+
+            PostDTO post2DTO = postDTOs.get(1);
+
+            assertEquals(2L, post2DTO.getId().longValue());
+            assertEquals(1, post2DTO.getComments().size());
+            assertEquals(3L, post2DTO.getComments().get(0).getId().longValue());
+        } );
+    }
+
+    @Entity(name = "Post")
+    @Table(name = "post")
+    public static class Post {
+
+        @Id
+        private Long id;
+
+        private String title;
+
+        @Column(name = "created_on")
+        private LocalDateTime createdOn;
+
+        @Column(name = "created_by")
+        private String createdBy;
+
+        @Column(name = "updated_on")
+        private LocalDateTime updatedOn;
+
+        @Column(name = "updated_by")
+        private String updatedBy;
+
+        @Version
+        private Short version;
+
+        @OneToMany(mappedBy = "post", cascade = CascadeType.ALL, orphanRemoval = true)
+        private List<PostComment> comments = new ArrayList<>();
+
+        public Long getId() {
+            return id;
+        }
+
+        public Post setId(Long id) {
+            this.id = id;
+            return this;
+        }
+
+        public String getTitle() {
+            return title;
+        }
+
+        public Post setTitle(String title) {
+            this.title = title;
+            return this;
+        }
+
+        public LocalDateTime getCreatedOn() {
+            return createdOn;
+        }
+
+        public Post setCreatedOn(LocalDateTime createdOn) {
+            this.createdOn = createdOn;
+            return this;
+        }
+
+        public String getCreatedBy() {
+            return createdBy;
+        }
+
+        public Post setCreatedBy(String createdBy) {
+            this.createdBy = createdBy;
+            return this;
+        }
+
+        public LocalDateTime getUpdatedOn() {
+            return updatedOn;
+        }
+
+        public Post setUpdatedOn(LocalDateTime updatedOn) {
+            this.updatedOn = updatedOn;
+            return this;
+        }
+
+        public String getUpdatedBy() {
+            return updatedBy;
+        }
+
+        public Post setUpdatedBy(String updatedBy) {
+            this.updatedBy = updatedBy;
+            return this;
+        }
+
+        public Short getVersion() {
+            return version;
+        }
+
+        public Post setVersion(Short version) {
+            this.version = version;
+            return this;
+        }
+
+        public List<PostComment> getComments() {
+            return comments;
+        }
+
+        public Post addComment(PostComment comment) {
+            comments.add(comment);
+            comment.setPost(this);
+            return this;
+        }
+    }
+
+    @Entity
+    @Table(name = "post_comment")
+    public static class PostComment {
+
+        @Id
+        private Long id;
+
+        @ManyToOne(fetch = FetchType.LAZY)
+        private Post post;
+
+        private String review;
+
+        public Long getId() {
+            return id;
+        }
+
+        public PostComment setId(Long id) {
+            this.id = id;
+            return this;
+        }
+
+        public Post getPost() {
+            return post;
+        }
+
+        public PostComment setPost(Post post) {
+            this.post = post;
+            return this;
+        }
+
+        public String getReview() {
+            return review;
+        }
+
+        public PostComment setReview(String review) {
+            this.review = review;
+            return this;
+        }
+    }
+
+    public static class PostDTO {
+
+        public static final String ID_ALIAS = "p_id";
+        public static final String TITLE_ALIAS = "p_title";
+
+        private Long id;
+
+        private String title;
+
+        private List<PostCommentDTO> comments = new ArrayList<>();
+
+        public PostDTO() {
+        }
+
+        public PostDTO(Long id, String title) {
+            this.id = id;
+            this.title = title;
+        }
+
+        public PostDTO(Object[] tuples, Map<String, Integer> aliasToIndexMap) {
+            this.id = AbstractTest.longValue(tuples[aliasToIndexMap.get(ID_ALIAS)]);
+            this.title = AbstractTest.stringValue(tuples[aliasToIndexMap.get(TITLE_ALIAS)]);
+        }
+
+        public Long getId() {
+            return id;
+        }
+
+        public void setId(Number id) {
+            this.id = id.longValue();
+        }
+
+        public String getTitle() {
+            return title;
+        }
+
+        public void setTitle(String title) {
+            this.title = title;
+        }
+
+        public List<PostCommentDTO> getComments() {
+            return comments;
+        }
+    }
+
+    public static class PostCommentDTO {
+        public static final String ID_ALIAS = "pc_id";
+        public static final String REVIEW_ALIAS = "pc_review";
+
+        private Long id;
+
+        private String review;
+
+        public PostCommentDTO(Long id, String review) {
+            this.id = id;
+            this.review = review;
+        }
+
+        public PostCommentDTO(Object[] tuples, Map<String, Integer> aliasToIndexMap) {
+            this.id = AbstractTest.longValue(tuples[aliasToIndexMap.get(ID_ALIAS)]);
+            this.review = AbstractTest.stringValue(tuples[aliasToIndexMap.get(REVIEW_ALIAS)]);
+        }
+
+        public Long getId() {
+            return id;
+        }
+
+        public void setId(Number id) {
+            this.id = id.longValue();
+        }
+
+        public void setId(Long id) {
+            this.id = id;
+        }
+
+        public String getReview() {
+            return review;
+        }
+
+        public void setReview(String review) {
+            this.review = review;
+        }
+    }
+
+    public static class PostDTOTupleTransformer implements TupleTransformer {
+
+        private Map<Long, PostDTO> postDTOMap = new LinkedHashMap<>();
+
+        @Override
+        public PostDTO transformTuple(Object[] tuple, String[] aliases) {
+            Map<String, Integer> aliasToIndexMap = aliasToIndexMap(aliases);
+            Long postId = AbstractTest.longValue(tuple[aliasToIndexMap.get(PostDTO.ID_ALIAS)]);
+
+            PostDTO postDTO = postDTOMap.computeIfAbsent(
+                postId,
+                id -> new PostDTO(tuple, aliasToIndexMap)
+            );
+            postDTO.getComments().add(new PostCommentDTO(tuple, aliasToIndexMap));
+
+            return postDTO;
+        }
+
+        private Map<String, Integer> aliasToIndexMap(String[] aliases) {
+            Map<String, Integer> aliasToIndexMap = new LinkedHashMap<>();
+            for (int i = 0; i < aliases.length; i++) {
+                aliasToIndexMap.put(aliases[i].toLowerCase(Locale.ROOT), i);
+            }
+            return aliasToIndexMap;
+        }
+    }
+}