Spring JPA delete entity not working when iterating - spring-boot

Question

I am trying to delete an entity using its remove method of its repository from another service class, but it is not getting deleted. Below code works when I hard code the Id:
long id = 1234;
Optional<Employee> employeeOptional = employeeRepository.findById(id);
Employee employee = employeeOptional.get();
employeeRepository.delete(employee);
Above code is working fine, but if I try with below code, deletion is not happening.
for (Employee employee : department.getEmployees()) {
if (employee.getRole().equals("Manager")) {
employeeRepository.delete(employee);
}
}
I am trying the code from DepartmentServiceImpl class, but above is not working, but same when id is hardcoded it works.
Inside Department I have relationship like below,
#OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "deal")
private Set<Employee> employees= new HashSet<>();
And inside Employee I have like below,
#ManyToOne
#JoinColumn(name = "department_id", referencedColumnName = "department_id")
private Department department;
How can I fix this issue?

Answer 1

You are attempting to delete Employees, but your entities still have references to each other.
A better way to delete an employee is to use orphan removal and remove the employee from the collection which will trigger a delete.
Also mappedBy = "deal" should be the name of the attribute on the owning side of the relationship so this should be mappedBy = "department"
#OneToMany(
cascade = CascadeType.ALL,
mappedBy = "department",
orphanRemoval = true
)
private Set<Employee> employees= new HashSet<>();
add a method to Department to remove the Employee and keep the bidirectional relationship in sync by also removing Department from Employee
public void removeEmployee(Employee employee) {
employees.removeEmployee(employee);
employee.setDepartment(null);
}
you can then remove the 'Managers' from your Employees collection which should trigger the delete statements
List<Employee> managers = department.getEmployees.stream()
.filter(e -> e.getRole().equals("Manager"))
.collect(Collectors.toList());
for (Employee manager : managers) {
department.removeEmployee(manager);
}

Answer 2

Not tested but should work fine:
Try tweaking your code a little like this:
Set<Employee>employees= new HashSet<>();
for (Employee employee : department.getEmployees()) {
if (employee.getRole().equals("Manager")) {
employees.add(employee);
}
}
department.setEmployees(employees);//I assume you have a setter
departmentRepository.save(department); //I hope you understand what departmentRepository means
Here you are reassigning the valid employees list.
You could follow another method, instead of deleting each entity separately, you could call a bulk-save using saveAll(...) method on the valid list.