Question

hibernate一对多怎么注解

Answer 1

hibernate.cfg.xml同上 加入Classes 、Student
Classes.java
package com.yulin.hibernate.pojo;
import java.util.LinkedHashSet;
import java.util.Set;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

@Entity
@Table(name="class")
public class Classes extends Base {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column
private Integer id;

@Column
private String className;

@Column
private Integer classNum;

// cascade表示级联操作
// CascadeType.MERGE级联更新：若items属性修改了那么order对象保存时同时修改items里的对象。对应EntityManager的merge方法
// CascadeType.PERSIST级联刷新：获取order对象里也同时也重新获取最新的items时的对象。对应EntityManager的refresh(object)方法有效。即会重新查询数据库里的最新数据
// CascadeType.REFRESH级联保存：对order对象保存时也对items里的对象也会保存。对应EntityManager的presist方法
// CascadeType.REMOVE级联删除：对order对象