Hibernate:JPA的一对多操作
作者:互联网
实体类Cla.java
@Entity
@Table(name = "cla")
public class Cla {
@Id
@Column(name = "cla_id")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer claId;
@Column(name = "cla_name")
private String claName;
@OneToMany(targetEntity = Stu.class, mappedBy = "cla", cascade = CascadeType.ALL, fetch = FetchType.LAZY) // mappedBy="对方的属性":表示两个表关系之间的控制权交给对方
private Set<Stu> stu = new HashSet<Stu>(0);
实体类Stu.java
@Entity
@Table(name = "stu")
public class Stu {
@Id
@Column(name = "stu_id")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer stuId;
@Column(name = "stu_name")
private String stuName;
@ManyToOne(targetEntity = Cla.class)
// joinColumns:建立主表与从表外键关系
// name属性:从表的外键字段名
// referencedColumnName属性:主表的主键字段名
@JoinColumn(name = "cla_id", referencedColumnName = "cla_id")
private Cla cla;
一对多保存
public void save() {
Cla cla = new Cla();
cla.setClaName("体育生");
Stu stu = new Stu();
stu.setStuName("赵云");
cla.getStu().add(stu);
stu.setCla(cla);
EntityManager entityManager = JPAUtils.createEntityManager();
EntityTransaction entityTransaction = entityManager.getTransaction();
entityTransaction.begin();
entityManager.persist(cla);
entityManager.persist(stu);
entityTransaction.commit();
entityManager.close();
}
级联更新
public void update() {
Stu stu = new Stu();
stu.setStuName("吕布");
EntityManager entityManager = JPAUtils.createEntityManager();
EntityTransaction entityTransaction = entityManager.getTransaction();
entityTransaction.begin();
Cla cla = entityManager.find(Cla.class, 1);
cla.getStu().add(stu);
stu.setCla(cla);
entityTransaction.commit();
entityManager.close();
}
级联删除
public void remove() {
EntityManager entityManager = JPAUtils.createEntityManager();
EntityTransaction entityTransaction = entityManager.getTransaction();
entityTransaction.begin();
Cla cla = entityManager.find(Cla.class, 1);
entityManager.remove(cla);
entityTransaction.commit();
entityManager.close();
}
对象导航查询
public void query() {
EntityManager entityManager = JPAUtils.createEntityManager();
EntityTransaction entityTransaction = entityManager.getTransaction();
entityTransaction.begin();
Cla cla = entityManager.find(Cla.class, 1);
System.out.println(cla);
Set<Stu> stus = cla.getStu();
System.out.println(stus);
entityTransaction.commit();
entityManager.close();
}
标签:entityManager,name,JPA,cla,Cla,stu,Hibernate,一对,entityTransaction 来源: https://blog.csdn.net/lovecuidong/article/details/100134364