我有三个表格来存放学生信息,第二个存放班级信息。三是对学生和班级studentclass表进行关联JPA:在表关联关系中级联
的实体和关系给出如下
class Student
{
@Id
@Column(name="STUDENT_ID")
long studentId;
@OneToMany(cascade=CascadeType.ALL,mappedBy="student")
Set<StudentClass> studentClasses
}
class Class
{
@Id
@Column(name="CLASS_ID")
long classId;
@OneToMany(cascade=CascadeType.ALL,mappedBy="class")
Set<StudentClass> studentClasses
}
class StudentClass
{
@Id
@Column(name="STUDENT_CLASS_ID")
long studentClassid;
@ManyToOne
@JoinColumn(name="STUDENT_ID")
private Student student;
@ManyToOne(cascade=CascadeType.ALL)
@JoinColumn(name="CLASS_ID")
private Class class;
}
class persist{
public void persist(){
Student student1 = new Student();
Class class1 = new Class();
session.save(class1);
StudentClass studentClass = new StudentClass();
studentClass.setClass(class1);
studentClass.setStudent(student1);
student1.getStudentClasses().add(studentClass);
session.save(student1);
session.getTransaction().commit();
}
}
以上持久性逻辑正常工作,因为我救单独的Class1,最后学生课。但是如果我试图单独保存student1,那么class1并没有得到保存?如果答案是课堂,学生不直接相关,那么当我尝试获取学生时,如何获取所有课程