Issue
I'm trying to map DTOs to entities. I created a service that only takes care of mapping objects - ObjectMapper. DTO objects have relationships with each other. When I map a single object, for example when I create User, Group, Note, everything works. But when I want to use a method that returns a Note with a specific ID - /notes/{id}, I get the following error.
Handler dispatch failed; nested exception is java.langStackOverflowError] with root cause
To get specific Note, I need to use this mapping method that also cause this error. As u can see, I have to also convert Group and Tags.
//Note
public NoteDTO NoteEntityToDtoGet(Note note) {
NoteDTO noteDTO = new NoteDTO();
noteDTO.setId(note.getId());
noteDTO.setTitle(note.getTitle());
noteDTO.setDescription(note.getDescription());
noteDTO.setGroup(GroupEntityToDtoGet(note.getGroup()));
noteDTO.setTags(TagConvertSet(note.getTags()));
return noteDTO;
}
When I don't have relationships defined as another DTO in the DTO class, but as an entity, everything works, since I don't have to convert the DTO to an entity.
Do you know where I'm making a mistake when mapping? Am I making a mistake in mapping multiple objects at once?
ObjectMapper
@Service
public class ObjectMapper {
//User
public UserDTO UserEntityToDtoGet(User user) {
UserDTO userDTO = new UserDTO();
userDTO.setId(user.getId());
userDTO.setName(user.getName());
userDTO.setEmail(user.getEmail());
userDTO.setGroup(user.getGroups());
return userDTO;
}
private UserCreationDTO UserEntityToDtoCreate(User user) {
UserCreationDTO userCreationDTO = new UserCreationDTO();
userCreationDTO.setName(user.getName());
userCreationDTO.setEmail(user.getEmail());
return userCreationDTO;
}
private User UserDtoToEntityCreate(UserCreationDTO userCreationDTO) {
User user = new User();
user.setName(userCreationDTO.getName());
user.setEmail(userCreationDTO.getEmail());
return user;
}
//Group
public GroupDTO GroupEntityToDtoGet(Group group) {
GroupDTO groupDTO = new GroupDTO();
groupDTO.setId(group.getId());
groupDTO.setName(group.getName());
groupDTO.setUser(UserEntityToDtoGet(group.getUser()));
groupDTO.setNotes(NoteConvertList(group.getNotes()));
groupDTO.setTags(TagConvertSet(group.getTags()));
return groupDTO;
}
public GroupCreationDTO GroupEntityToDtoCreate(Group group) {
GroupCreationDTO groupCreationDTO = new GroupCreationDTO();
groupCreationDTO.setName(group.getName());
groupCreationDTO.setUser(UserEntityToDtoGet(group.getUser()));
groupCreationDTO.setTags(TagConvertSet(group.getTags()));
return groupCreationDTO;
}
public Group GroupDtoToEntityCreate(GroupCreationDTO groupCreationDTO) {
Group group = new Group();
group.setName(groupCreationDTO.getName());
return group;
}
//Note
public NoteDTO NoteEntityToDtoGet(Note note) {
NoteDTO noteDTO = new NoteDTO();
noteDTO.setId(note.getId());
noteDTO.setTitle(note.getTitle());
noteDTO.setDescription(note.getDescription());
noteDTO.setGroup(GroupEntityToDtoGet(note.getGroup()));
noteDTO.setTags(TagConvertSet(note.getTags()));
return noteDTO;
}
public Note NoteDtoToEntityCreate(NoteCreationDTO noteCreationDTO) {
Note note = new Note();
note.setTitle(noteCreationDTO.getTitle());
note.setDescription(noteCreationDTO.getDescription());
return note;
}
public NoteCreationDTO NoteEntityToDtoCreate(Note note) {
NoteCreationDTO noteCreationDTO = new NoteCreationDTO();
noteCreationDTO.setTitle(note.getTitle());
noteCreationDTO.setDescription(note.getDescription());
return noteCreationDTO;
}
public List<NoteDTO> NoteConvertList(List<Note> note) {
return note.stream()
.map(this::NoteEntityToDtoGet)
.collect(Collectors.toList());
}
//Tag
public TagDTO TagEntityToDtoGet(Tag tag) {
TagDTO tagDTO = new TagDTO();
tagDTO.setId(tag.getId());
tagDTO.setName(tag.getName());
tagDTO.setNotes(tag.getNotes());
tagDTO.setGroups(tag.getGroups());
return tagDTO;
}
public TagCreationDTO TagEntityToDtoCreate(Tag tag) {
TagCreationDTO tagCreationDTO = new TagCreationDTO();
tagCreationDTO.setId(tag.getId());
tagCreationDTO.setName(tag.getName());
tagCreationDTO.setNotes(tag.getNotes());
return tagCreationDTO;
}
public Set<TagDTO> TagConvertSet(Set<Tag> groups) {
return groups.stream()
.map(this::TagEntityToDtoGet)
.collect(Collectors.toSet());
}
}
Solution
You get StackOverFlowError
because you end up with infinite recursive methods call and your application creates infinite amount of objects, so you just run out of memory:
1) your NoteEntityToDtoGet
method gets Note
's group and calls GroupEntityToDtoGet
method on the Group
object;
2) in GroupEntityToDtoGet
method you get all Group
's notes and call NoteConvertList
method on them, which calls NoteEntityToDtoGet
on each of the 'Note'
3) step 1 again...
... the same cycle goes over and over without a stop until your stack memory, you know, overflows :)
So you should decide do your DTO classes really need to hold references to other entity collections.
Answered By - AndrewThomas
Answer Checked By - Katrina (JavaFixing Volunteer)