Hibernate #ManyToMany org.hibernate.LazyInitializationException - spring

Question

I want to deal with common error, but I cannot find the right answer.
the error is:
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: newsProject.post.entity.Tag.posts, could not initialize proxy - no Session
How to avoid use of #Transactional?
I am trying to do the following actions in my SpringBootTest:
#SpringBootTest
#ActiveProfiles("test")
class PostRepositoryTest {
#Autowired
private PostRepository postRepository;
#Autowired
private TagRepository tagRepository;
#AfterEach
void deleteFromDB(){
postRepository.deleteAll();
tagRepository.deleteAll();
}
#Test
void deletePostWithMultipleTags(){
Post post = new Post();
Tag tag = new Tag(1L,"tag1", null);
Tag tag2 = new Tag(2L,"tag2", null);
Tag tag3 = new Tag(3L,"tag3", null);
tagRepository.save(tag);
tagRepository.save(tag2);
tagRepository.save(tag3);
post.setTitle("testTitle");
Tag tagNew = tagRepository.findByTagName(tag.getTagName());
post.addTag(tagNew);
post.addTag(tagRepository.findByTagName(tag2.getTagName()));
post.addTag(tagRepository.findByTagName(tag3.getTagName()));
System.out.println(post);
postRepository.save(post);
}
}
The error is in this part:
public void addTag(Tag tag) {
tags.add(tag);
tag.getPosts().add(this);
}
I am open for any additional questions that related to this problem
I do not want to use following answers:
- Fetch.EAGER (or something related with turning down Fetch.LAZY)
- hibernate.enable_lazy_load_no_trans=True
The code:
Post.java
#Entity
#Data
#Table
#NoArgsConstructor
#AllArgsConstructor
public class Post {
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "post_generator")
#SequenceGenerator(name="post_generator", sequenceName = "seq_post", allocationSize = 1)
private Long id;
#Enumerated(EnumType.STRING)
private Status status;
//Some code
#ManyToMany(cascade = {
CascadeType.PERSIST,
CascadeType.MERGE
})
#JoinTable(
name = "post_tag",
joinColumns = {#JoinColumn(name = "post_id")},
inverseJoinColumns = {#JoinColumn(name = "tag_id")})
private List<Tag> tags = new ArrayList<>();
public void addTag(Tag tag) {
tags.add(tag);
tag.getPosts().add(this);
}
public void removeTag(Tag tag) {
tags.remove(tag);
tag.getPosts().remove(this);
}
}
Tag.java
#Entity
#Data
#Table
#NoArgsConstructor
#AllArgsConstructor
#ToString(exclude = "posts")
public class Tag {
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "id_generator")
#SequenceGenerator(name="id_generator", sequenceName = "seq_tag", allocationSize = 1)
private Long id;
private String tagName;
#ManyToMany(mappedBy="tags")
List<Post> posts = new ArrayList<>();
public void addPost(Post post) {
posts.add(post);
post.getTags().add(this);
}
public void removePost(Post post) {
posts.remove(post);
post.getTags().remove(this);
}
}

Answer 1

i tried your case and this is working for me. Please try :
#Test
#Transactional
public void test() {
Post post = new Post();
post.setTitle("post");
Tag tag1 = new Tag();
tag1.setTagName("tag1");
tag1.getPosts().add(post);
Tag tag2 = new Tag();
tag2.setTagName("tag2");
tag2.getPosts().add(post);
post.getTags().add(tag1);
post.getTags().add(tag2);
postRepository.save(post1);
}
We benefit of cascade saving here. Don't forget to add #Transactional to your method.

Answer 2

The answer is simple. We can avoid #Transactional 100%.
Add the following lines to the testing class:
#DataJpaTest
#AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
#Rollback(false)
#ActiveProfiles("test")
class PostRepositoryTest {
as we are testing work of JPA.
Use in the repository interface extends JpaRepository<..., ...> instead of CrudRepository<..., ...>
in tagRepository add the line:
List<Tag> findByNameIn(List<String> names);
see documentation.
Now we can modify or test to this:
#Test
void deletePostWithMultipleTags(){
Tag tag = new Tag(1L,"tag1", null);
Tag tag2 = new Tag(2L,"tag2", null);
Tag tag3 = new Tag(3L,"tag3", null);
tagRepository.saveAll(Arrays.asList(tag, tag2, tag3));
tagRepository.flush();
Post post = new Post();
post.setTitle("testTitle");
List<Tag> tags = tagRepository.findByNameIn(Arrays.asList(tag.getName(), tag2.getName(), tag3.getName(),));
for (Tag tagItem : tags){
post.addTag(tahItem);
}
postRepository.saveAndFlush(post);
}
After all these actions you can avoid the use of #Transactional

Answer 3

The quick fix would be either:
Annotate your test method with #Transactional (which will rollback all changes and has maybe unwanted side-effects. see this link for more information)
Annotate your test method with #Rollback(false), which will span a transaction around your test and not rollback.