Hibernnate 一对多多对一双向关联

Group.java

    package com.bjsxt.hibernate;
    
    import java.util.HashSet;
    import java.util.Set;
    
    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    import javax.persistence.JoinColumn;
    import javax.persistence.OneToMany;
    import javax.persistence.Table;
    
    @Entity
    @Table(name="t_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")
        
        public Set<User> getUsers() {
            return users;
        }
        public void setUsers(Set<User> users) {
            this.users = users;
        }
    }

User.java

package com.bjsxt.hibernate;

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

@Entity
@Table(name="t_user")
public class User {
    private int id;
    private String name;
    private Group group;
    @ManyToOne
    public Group getGroup() {
        return group;
    }
    public void setGroup(Group group) {
        this.group = group;
    }
    @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;
    }
}

Xml方式

user.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
    <class name="com.bjsxt.hibernate.User" table="t_user">
        <id name="id">
            <generator class="native"></generator>
        </id>
        
        <property name="name"></property>
        <many-to-one name="group" column="groupId"></many-to-one>
    </class>
    
</hibernate-mapping>

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
    <class name="com.bjsxt.hibernate.Group" table="t_group">
        <id name="id">
            <generator class="native"></generator>
        </id>
        
        <property name="name"></property>
        <set name="users">
            <key column="groupId"></key>
            <one-to-many class="com.bjsxt.hibernate.User"/>
        </set>
    </class>
    
</hibernate-mapping>