Jpa雙向關聯表（Teacher->Student）保存時遇到一個問題，保存Student（多方）時通過資料庫查詢并設定其關聯的Teacher（在資料庫中已存在，id為1）.試了很多辦法，沒辦法保存外鍵teacherId。請各位支招：）
錯誤資訊：detached entity passed to persist: com.ld.entity.Teacher，（貌似物件內部形成了回圈包含了）。
代碼如下：
物體類：Teacher
@Entity
@Data
public class Teacher {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
Long id;
String name;
@OneToMany(mappedBy="teacher", cascade = CascadeType.ALL)
private List<Student> students;
}
物體類：Student
@Entity
@Data
public class Student {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
private Integer age;
@Transient
private Long teacherId;
@ManyToOne(cascade = CascadeType.ALL, fetch=FetchType.LAZY)
@JoinColumn(name = "teacherId")
private Teacher teacher;
}
測驗類：
@Test
void addStudent() {
Student student = new Student();
student.setAge(14);
student.setName("小成");
Teacher teacher = teacherDao.findById(1L).get();
student.setTeacher(teacher);
studentDao.save(student);
}
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標籤：Java EE
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