開發環境：Mysql+Eclipse

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一對多單向的列子原理：一個班級，多個學生，學生端為多的一端，他們擁有一個外鍵指向相同的班級。

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項目結構

需要的jar包

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hibernate.cfg.xml

?? ?<!-- 配置mysql數據庫的連接參數 -->
?? ??? ?
?? ??? ??? ?<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
?? ??? ??? ?<!-- 驅動程序名 -->
?? ??? ??? ?<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
?? ??? ??? ?<!-- 自動創建表 -->
?? ??? ??? ?<property name="hbm2ddl.auto">update</property>
?? ??? ??? ?<!-- 控制臺打印sql語句 -->
?? ??? ??? ?<property name="show_sql">true</property>?
?? ??? ??? ?<!-- 數據庫名 -->
?? ??? ??? ?<property name="hibernate.connection.url">jdbc:mysql://localhost/test</property>
?? ??? ??? ?<!-- 用戶名 -->
?? ??? ??? ?<property name="hibernate.connection.username">root</property>
?? ??? ??? ?<!-- 密碼 -->
?? ??? ??? ?<property name="hibernate.connection.password"></property>
?? ??? ??? ?<!-- 對應的實體 -->
?? ??? ??? ?<mapping class="cn.dao.Classes"/>
?? ??? ??? ?<mapping class="cn.dao.Student"/>
?? ?</session-factory>

實體類：

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;
?? ?}

?? ?//測試打印
?? ?@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;
?? ?}
?? ?
?? ?
}
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創建一個打開session的工具類：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 {
?? ??? ?// 讀取Hibernate的配置文件，進行初始化的操作
?? ??? ?Configuration config = new Configuration().configure();
?? ??? ?StandardServiceRegistryBuilder ssrb = new StandardServiceRegistryBuilder().applySettings(config.getProperties());
?? ??? ?StandardServiceRegistry registry = ssrb.build();
?? ??? ?sessionFactory = config.buildSessionFactory(registry);
?? ?}

?? ?/**
?? ? * 獲取SessionFactory
?? ? */

?? ?public static SessionFactory getSessionFactory() {
?? ??? ?return sessionFactory;
?? ?}

?? ?/**
?? ? * 獲取session
?? ? */

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

?? ?/**
?? ? * 關閉session
?? ? */

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

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最后一個測試，實現簡單的增刪改查功能：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;

/**
?* 單向的一對多關聯操作
?*?
?* @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());
?? ??? ?}
?? ?}
}
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