OneToMany Relationship: referenced id is null - spring boot - spring-boot

Question

I'm new to Spring-Data-Jpa so my question is may a bit silly. I'm stuck and would be glad to get help.
I have a entity base model and two entities with following structure:
#SuperBuilder(toBuilder = true)
#NoArgsConstructor
#AllArgsConstructor
#MappedSuperclass
public class BaseModel {
#Id
#GeneratedValue(generator = "system-uuid")
#GenericGenerator(name = "system-uuid", strategy = "uuid")
private String id;
...more attributes + getter & setter
}
#Entity
#SuperBuilder(toBuilder = true)
#AllArgsConstructor
#NoArgsConstructor
#Table(name = "project")
public class Project extends BaseModel {
#Column
private String name;
#OneToMany(cascade = CascadeType.ALL,
fetch = FetchType.LAZY,
mappedBy = "project")
private List<Announcement> announcements = new ArrayList<>();
...more attributes + getter & setter
}
#Entity
#SuperBuilder(toBuilder = true)
#AllArgsConstructor
#NoArgsConstructor
#Table(name = "announcement")
public class Announcement extends BaseModel {
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name="project_id", nullable = false)
private Project project;
...more attributes + getter & setter
}
I persist my Project and Announcement Entity as follows:
public ProjectDTO createProject(CreateProjectRequest request) {
Project projectEntity = projectRepository.save(
Project.builder()
.announcements(request.getAnnouncements() != null
? request.getAnnouncements().stream().map(dto -> modelMapper.map(dto, Announcement.class)).toList()
: null)
.history(List.of(
HistoryEntry.builder()
.action(Action.PROJECT_CREATED.getValue())
.build())
)
.status(Status.NEW)
.name(request.getName())
.build()
);
return modelMapper.map(projectEntity, ProjectDTO.class);
}
I activated JPA SQL Statement trace with values.
Here you can see that the binding parameter 3 (foreign key for project) in the second statement is null. There is also no follow-up update in announcement entity for the foreign key value.
How can i fix that?
Hibernate:
/* insert de.keycon.salesservice.model.entity.Project
*/ insert
into
project
(created, updated, name, status, id)
values
(?, ?, ?, ?, ?)
09:36:32.263 [http-nio-8081-exec-3] TRACE org.hibernate.type.descriptor.sql.BasicBinder - binding parameter [1] as [TIMESTAMP] - [2022-11-29T09:36:32.254055300]
09:36:32.264 [http-nio-8081-exec-3] TRACE org.hibernate.type.descriptor.sql.BasicBinder - binding parameter [2] as [TIMESTAMP] - [2022-11-29T09:36:32.255054700]
09:36:32.264 [http-nio-8081-exec-3] TRACE org.hibernate.type.descriptor.sql.BasicBinder - binding parameter [3] as [VARCHAR] - [Demo-Project]
09:36:32.264 [http-nio-8081-exec-3] TRACE org.hibernate.type.descriptor.sql.BasicBinder - binding parameter [4] as [VARCHAR] - [NEW]
09:36:32.264 [http-nio-8081-exec-3] TRACE org.hibernate.type.descriptor.sql.BasicBinder - binding parameter [5] as [VARCHAR] - [2c9fe08184c287bc0184c287d3600000]
Hibernate:
/* insert de.keycon.salesservice.model.entity.Announcement
*/ insert
into
announcement
(created, updated, project_id, requirement, id)
values
(?, ?, ?, ?, ?)
09:36:32.267 [http-nio-8081-exec-3] TRACE org.hibernate.type.descriptor.sql.BasicBinder - binding parameter [1] as [TIMESTAMP] - [2022-11-29T09:36:32.267443100]
09:36:32.267 [http-nio-8081-exec-3] TRACE org.hibernate.type.descriptor.sql.BasicBinder - binding parameter [2] as [TIMESTAMP] - [2022-11-29T09:36:32.267443100]
09:36:32.267 [http-nio-8081-exec-3] TRACE org.hibernate.type.descriptor.sql.BasicBinder - binding parameter [3] as [VARCHAR] - [null]
09:36:32.267 [http-nio-8081-exec-3] TRACE org.hibernate.type.descriptor.sql.BasicBinder - binding parameter [4] as [VARCHAR] - [Java 11, Cloud Native Experience, Maven or Gradle, Experience with Testing Framework]
09:36:32.267 [http-nio-8081-exec-3] TRACE org.hibernate.type.descriptor.sql.BasicBinder - binding parameter [5] as [VARCHAR] - [2c9fe08184c287bc0184c287d3730001]
EDIT:
I have already tried:
#JsonManagedReference and #JsonBackReference.
Change fetch.Lazy to fetch.Eager.
Set referencedColumnName = "id".

Answer 1

I answer my own question. I changed my createProject method to keep project also in announcements before persisting them. Now the id is correctly reflected.
public ProjectDTO createProject(CreateProjectRequest request) {
List<Announcement> announcements = request.getAnnouncements() != null
? request.getAnnouncements().stream().map(dto -> modelMapper.map(dto, Announcement.class)).toList()
: null;
Project project = Project.builder()
.announcements(announcements)
.history(List.of(
HistoryEntry.builder()
.action(Action.PROJECT_CREATED.getValue())
.build())
)
.status(Status.NEW)
.name(request.getName())
.build();
for (var announcement: announcements) {
announcement.setProject(project);
}
Project projectEntity = projectRepository.save(
project
);
return modelMapper.map(projectEntity, ProjectDTO.class);
}