Hibernate学习系列————注解一对多单向实例

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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

<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
           
           <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
           
           <property name="hbm2ddl.auto">update</property>
           
           <property name="show_sql">true</property>
           
           <property name="hibernate.connection.url">jdbc:mysql://localhost/test</property>
           
           <property name="hibernate.connection.username">root</property>
           
           <property name="hibernate.connection.password"></property>
           
           <mapping class="cn.dao.Classes"/>
           <mapping class="cn.dao.Student"/>
   </session-factory>

实体类：

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());
       }
   }
}