开发环境：Mysql+Eclipse

一对多单向的列子原理：一个班级，多个学生，学生端为多的一端，他们拥有一个外键指向相同的班级。

项目结构

需要的jar包

hibernate.cfg.xml

<!-- 配置mysql数据库的连接参数 -->
        
            <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
            <!-- 驱动程序名 -->
            <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
            <!-- 自动创建表 -->
            <property name="hbm2ddl.auto">update</property>
            <!-- 控制台打印sql语句 -->
            <property name="show_sql">true</property> 
            <!-- 数据库名 -->
            <property name="hibernate.connection.url">jdbc:mysql://localhost/test</property>
            <!-- 用户名 -->
            <property name="hibernate.connection.username">root</property>
            <!-- 密码 -->
            <property name="hibernate.connection.password"></property>
            <!-- 对应的实体 -->
            <mapping class="cn.dao.Classes"/>
            <mapping class="cn.dao.Student"/>
    </session-factory>

实体类：

1. Classes.java

package cn.dao;

import java.io.Serializable;
import java.util.HashSet;
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.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.Table;

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

private Long id;

private String name;

private String desc;

private Set<Student> students = new HashSet<Student>();

@Id
    @Column(name = "cid")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    public Long getId() {
        return id;
    }

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

@Column(name = "cname")
    public String getName() {
        return name;
    }

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

@Column(name = "cdesc")
    public String getDesc() {
        return desc;
    }

public void setDesc(String desc) {
        this.desc = desc;
    }

@OneToMany(fetch = FetchType.LAZY, cascade = { CascadeType.ALL })
    @JoinColumn(name = "cid")
    public Set<Student> getStudents() {
        return students;
    }

public void setStudents(Set<Student> students) {
        this.students = students;
    }

//测试打印
    @Override
    public String toString() {
        return "Classes [id=" + id + ", name=" + name + ", desc=" + desc + ", students=" + students + "]";
    }

}

2.Student.java

package cn.dao;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "student")
public class Student implements Serializable {
    
    private Long id;
    
    private String name;
    
    private String sex;
    
    @Id
    @Column(name = "sid")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    public Long getId() {
        return id;
    }

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

@Column(name = "sname")
    public String getName() {
        return name;
    }

public void setName(String name) {
        this.name = name;
    }
    
    @Column(name = "sex")
    public String getSex() {
        return sex;
    }

public void setSex(String sex) {
        this.sex = sex;
    }
    
    
}

创建一个打开session的工具类：HibernateUtil

package cn.utils;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {

private static SessionFactory sessionFactory;
    private static Session session;

static {
        // 读取Hibernate的配置文件，进行初始化的操作
        Configuration config = new Configuration().configure();
        StandardServiceRegistryBuilder ssrb = new StandardServiceRegistryBuilder().applySettings(config.getProperties());
        StandardServiceRegistry registry = ssrb.build();
        sessionFactory = config.buildSessionFactory(registry);
    }

/**
     * 获取SessionFactory
     */

public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }

/**
     * 获取session
     */

public static Session getSession() {
        return sessionFactory.openSession();
    }

/**
     * 关闭session
     */

public static void closeSession() {
        if (session != null) {
            session.close();
        }
    }
}

最后一个测试，实现简单的增删改查功能：OneToMany.java

package cn.test;

import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;
import cn.dao.Classes;
import cn.dao.Student;
import cn.utils.HibernateUtil;

/**
 * 单向的一对多关联操作
 * 
 * @author hasee
 *
 */
public class OneToMany {
    
    public static void main(String[] args) {
         query();
    }

public static void save() {
        Session session = HibernateUtil.getSession();
        Transaction transaction = session.beginTransaction();
        Classes classes = new Classes();
        classes.setName("ClassOne");
        classes.setDesc("This is ClassOne");
        Set<Student> students = new HashSet<Student>();
        Student student = new Student();
        student.setName("Mike");
        student.setSex("boy");
        students.add(student);
        classes.setStudents(students);
        session.save(classes);
        transaction.commit();
        HibernateUtil.closeSession();
    }

public static void edit(){
        Session session = HibernateUtil.getSession();
        Transaction transaction = session.beginTransaction();
        Classes classes = (Classes) session.get(Classes.class, 1L);
        Set<Student> students = classes.getStudents();
        for (Student student : students) {
            student.setName("Jary");
        }
        transaction.commit();
        HibernateUtil.closeSession();
    }
    
    public static void delete(){
        Session session = HibernateUtil.getSession();
        Transaction transaction = session.beginTransaction();
        Classes classes = (Classes) session.get(Classes.class, 1L);
        session.delete(classes);
        transaction.commit();
        HibernateUtil.closeSession();
        
    }
    
    public static void query(){
        Session session = HibernateUtil.getSession();
        Query query = session.createQuery("from Classes");
        List<Classes> list = query.list();
        for (Classes classes : list) {
            System.out.println(classes.toString());
        }
    }
}