hibernate对象关联

user属于group

User源码：package com.dailei.hibernate.model;

import java.util.Date;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.EnumType;
import javax.persistence.Enumerated;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.IdClass;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
import javax.persistence.Transient;

@Entity
// 定义实体，和表对应
@Table(name = "t_user")
public class User {

private Group group;
private int id;
private String name;

//如果两个对象有关联，从A可以导向到B，默认情况下对A的保存不会影响到B
//需要先存B再存A，若想自动保存，设置cascade
//如果从B可以导向C
//在B上加上cascade
@ManyToOne(cascade={CascadeType.ALL})
public Group getGroup() {
return group;
}

@Id
// 定义主键
@GeneratedValue
public int getId() {
return id;
}

public String getName() {
return name;
}

public void setGroup(Group group) {
this.group = group;
}

public void setId(int id) {
this.id = id;
}

public void setName(String name) {
this.name = name;
}

}

group源码：package com.dailei.hibernate.model;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.Table;

@Entity
@Table(name="_group")
public class Group {
private int id;
private String name;
private Set<User> users = new HashSet<User>();

@Id
@GeneratedValue
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}

@OneToMany(mappedBy="group",cascade={CascadeType.ALL})
public Set<User> getUsers() {
return users;
}
public void setUsers(Set<User> users) {
this.users = users;
}

}

测试程序：package test.com.dailei.hibernate.model;

import java.util.HashSet;
import java.util.Set;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.tool.hbm2ddl.SchemaExport;

import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.Test;

import com.dailei.hibernate.model.Group;
import com.dailei.hibernate.model.User;

public class Test1 {

private static SessionFactory sf = null;
private static Session session = null;

@BeforeClass
public static void beforeClass() {
//有时候配置出错，有时候不给报错
try {
sf=new AnnotationConfiguration().configure().buildSessionFactory();
new SchemaExport(new AnnotationConfiguration().configure()).create(false,true);
}catch(Exception e) {
e.printStackTrace();
}
}

@Test
public void testSchemaExport() {
User user = new User();
user.setName("u1");
Group group = new Group();
group.setName("g1");
group.getUsers().add(user);

session = sf.getCurrentSession();
session.beginTransaction();
session.save(group);
user.setGroup(group);
// session.save(user);
session.getTransaction().commit();

}

@AfterClass
public static void afterClass() {

sf.close();
}
}