Search by list type field in Spring Data to check if empty or not - spring

Question

I have a Project entity and a separate entity to represent a project assigned to a user
public class Project {
// other fields
#OneToMany(fetch = FetchType.LAZY, mappedBy = "project")
private List<UserProject> projectAssignedUsers;
}
public class UserProject {
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "project_id")
private Project project;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "user_id")
private User user;
}
I need to write 2 separate queries that return the list of assigned projects and unassigned projects, this is what I have:
#Query("from Project p where p.country = :country and p.projectAssignedUsers != null order by p.name asc")
List<Project> getAssignedProjectsByCountry(String country, Pageable pageable);
#Query("from Project p where p.country = :country and p.projectAssignedUsers = null order by p.name asc")
List<Project> getUnassignedProjectsByCountry(String country, Pageable pageable);
However, I'm getting this error:
Caused by: org.postgresql.util.PSQLException: ERROR: syntax error at or near "."
How could I write such a query?

Answer 1

This is your first query transformed to plain SQL:
select project0_.id as id1_1_, project0_.country as country2_1_, project0_.name as name3_1_ from project project0_
cross join user_project projectass1_
where project0_.id=projectass1_.project_id
and project0_.country='Country'
and (. is not null)
order by project0_.name asc
The problem is here: and (. is not null).
You can fix it using joins:
#Query(value = "from Project as p left join p.projectAssignedUsers as u where p.country = :country and u is not null")
List<Project> getAssignedProjectsByCountry(String country, Pageable pageable);
#Query(value = "from Project as p left join p.projectAssignedUsers as u where p.country = :country and u is null")
List<Project> getUnassignedProjectsByCountry(String country, Pageable pageable);