Java中的JPA实体关系：JPA一对一,一对多(多对一),多对多

@Entity
public class Person {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    @OneToOne(mappedBy = "person")
    private Passport passport;
    // 省略getter和setter
}

@Entity
public class Passport {
    @Id
    private Long id;
    
    @OneToOne
    @JoinColumn(name = "person_id") // 明确外键列
    private Person person;
    // 省略getter和setter
}

@Entity
public class Department {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    @OneToMany(mappedBy = "department", cascade = CascadeType.PERSIST)
    private List<Employee> employees = new ArrayList<>();
    // 省略getter和setter
}

@Entity
public class Employee {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    @ManyToOne
    @JoinColumn(name = "department_id")
    private Department department;
    // 省略getter和setter
}

@Entity
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    @ManyToMany
    @JoinTable(
        name = "student_course",
        joinColumns = @JoinColumn(name = "student_id"),
        inverseJoinColumns = @JoinColumn(name = "course_id")
    )
    private Set<Course> courses = new HashSet<>();
    // 省略getter和setter
}

@Entity
public class Course {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    @ManyToMany(mappedBy = "courses")
    private Set<Student> students = new HashSet<>();
    // 省略getter和setter
}