如何正确地从另一个实体中删除一个实体？

Question

我使用Spring Data.有两个实体。我想解雇一名员工。如果我解雇一个员工。 1. 我将在实体Employee中删除一个职位（它将是空的）2。而在实体Position中，我将从一组雇员中删除该雇员。

我检查了 "fire "方法正确地从Position_Employees_JT表中删除，并且职位和雇员继续存在于数据库中。

但它是正确的方法或它更好地写一个查询（HQL或JPQL）？ 如果我想写一个更复杂的方法，什么语言更好地使用？

我去掉了getset和另一个不必要的代码。

@Entity
public class Employee {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long employeeId;

    private String firstName;

    @ManyToOne(cascade = ALL, fetch = LAZY)
    @JoinColumn(name = "fk_position")
    private Position position;

    public void removePosition(){
        this.position = null;
    }
}

@Entity
public class Position {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "POSITION_ID", updatable = false)
    private Long id;

    private PositionName name;

    @JoinTable(name = "Position_Employees_JT",
            joinColumns = @JoinColumn(name = "ID_POSITION", referencedColumnName = "POSITION_ID"),
            inverseJoinColumns = @JoinColumn(name = "ID_EMPLOYEE", referencedColumnName = "EMPLOYEE_ID"))
    @OneToMany
    private Set<Employee> employeeSet = new HashSet<>();

    public void addEmployee(Employee employee){
        employeeSet.add(employee);
    }

    public void removeEmployee(Employee employee){
        employeeSet.remove(employee);
    }
}

火 "方法。

@Transactional
public Employee fireEmployee(Long id) {
    Optional<Employee> employee = employeeRepository.findById(id);
    Optional<Position> position = positionRepository.findById(employee.get().getPosition().getId()); 
    position.get().removeEmployee(employee.get());
    employee.get().removePosition();
    return null;
}

Answer 1

下面的评论。

@Transactional
public Employee fireEmployee(Long id) {
    Optional<Employee> employee = employeeRepository.findById(id);
    Optional<Position> position = positionRepository.findById(employee.get().getPosition().getId()); 
    position.get().removeEmployee(employee.get()); //this only affects the set in the memory, will not affect the database record
    employee.get().remove(); //this will actually delete record from the database
    return null;
}

Answer 2

你一定是在Employee和Position之间有一个父子关系，我建议你只取到 雇员 从db中获取。它将获取各自的 位置 也是。

@Transactional
public Employee fireEmployee(Long id) {
    Optional<Employee> employee = employeeRepository.findById(id);
    employee.get().remove();
    return null;
}