Question

我想获取有关特定学生的课程详情。我怎么能在Hibernate中做到这一点？

请帮助我进入休眠状态。

@Entity
public class Course implements Serializable {

    private long id;
    private String name;

    @Id
    @GeneratedValue
    public long getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    @ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @JoinTable(name = "Enrollment", joinColumns = {
        @JoinColumn(name = "Course_Id", insertable = false, updatable = false, nullable = false)}, inverseJoinColumns = {
        @JoinColumn(name = "Student_Id", insertable = false, nullable = false, updatable = false)})
    private List<Student> students = new ArrayList<Student>();

}


@Entity
public class Student implements Serializable {

    private long id;
    private String name;

    @Id
    @GeneratedValue
    public long getId() {
        return id;
    }

}

帮助我查找有关学生课程的详细信息。

Answer 1

如果单个学生有多个课程，那么您的数据库结构应该是：

@Entity
@Table(name="Student")
public class Student implements Serializable {


private static final long serialVersionUID = 1L;


@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name="ID")
private long id;


@Column(name="NAME")
private String name;


@OneToMany(mappedBy="student",fetch = FetchType.EAGER)   // change to FetchType.Lazy for lazy initialization
private List<Courses> courses;

// Getters and setters
}

您的课程实体课程应该像

@Entity
@Table(name="Courses")
public class Courses {


@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name="COURSE_ID")
private long id;


@Column(name="COURSE_NAME")
private String name;


@ManyToOne
@JoinColumn(name="Student_ID")    // Foreign Key 
private Student student;

}

如果遇到延迟初始化的任何问题，请将此属性设置为true ＆＃34; hibernate.enable_lazy_load_no_trans＆＃34;

获取学生课程列表

1 个答案: