Hibernate实战——有序集合映射

左手的ㄟ右手 2021-07-24 13:55 450阅读 0赞

**一 配置文件**

<?xml version="1.0" encoding="GBK"?>
    
    <!DOCTYPE hibernate-configuration PUBLIC
         "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
         "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
    
    <hibernate-configuration>
         <session-factory>
               
               <property  name="connection.driver_class">com.mysql.jdbc.Driver</property>
               
               <property  name="connection.url">jdbc:mysql://localhost/hibernate</property>
               
               <property name="connection.username">root</property>
               
               <property name="connection.password">32147</property>
               
               <property  name="hibernate.c3p0.max_size">20</property>
               
               <property name="hibernate.c3p0.min_size">1</property>
               
               <property  name="hibernate.c3p0.timeout">5000</property>
               
               <property  name="hibernate.c3p0.max_statements">100</property>
               <property  name="hibernate.c3p0.idle_test_period">3000</property>
               <property  name="hibernate.c3p0.acquire_increment">2</property>
               <property  name="hibernate.c3p0.validate">true</property>
               
               <property  name="dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>
               
               <property name="hbm2ddl.auto">update</property>
               
               <property name="show_sql">true</property>
               
               <property name="hibernate.format_sql">true</property>
               
               <mapping class="org.crazyit.app.domain.Person"/>
         </session-factory>
    </hibernate-configuration>

**二 PO**

package org.crazyit.app.domain;
    
    import java.util.*;
    import javax.persistence.*;
    import org.hibernate.annotations.SortNatural;
    
    
    @Entity
    @Table(name="person_inf")
    public class Person
    {
        @Id @Column(name="person_id")
        @GeneratedValue(strategy=GenerationType.IDENTITY)
        // 标识属性
        private Integer id;
        private String name;
        private int age;
        // 有序集合属性
        @ElementCollection(targetClass=String.class)
        // 映射保存集合元素的表
        @CollectionTable(name="training_inf",
            joinColumns=@JoinColumn(name="person_id" , nullable=false))
        // 定义保存集合元素的数据列
        @Column(name="training_name" , nullable=false)
        // 使用@SortNatural指定使用自然排序
        @SortNatural
        private SortedSet<String> trainings
            = new TreeSet<>();
    
        // id的setter和getter方法
        public void setId(Integer id)
        {
            this.id = id;
        }
        public Integer getId()
        {
            return this.id;
        }
    
        // name的setter和getter方法
        public void setName(String name)
        {
            this.name = name;
        }
        public String getName()
        {
            return this.name;
        }
    
        // age的setter和getter方法
        public void setAge(int age)
        {
            this.age = age;
        }
        public int getAge()
        {
            return this.age;
        }
    
        // trainings的setter和getter方法
        public void setTrainings(SortedSet<String> trainings)
        {
            this.trainings = trainings;
        }
        public SortedSet<String> getTrainings()
        {
            return this.trainings;
        }
    }

**三 测试代码**

1 工具类

package lee;
    import org.hibernate.*;
    import org.hibernate.cfg.*;
    import org.hibernate.service.*;
    import org.hibernate.boot.registry.*;
    
    public class HibernateUtil
    {
         public static final SessionFactory sessionFactory;
         static
         {
               try
               {
                    // 使用默认的hibernate.cfg.xml配置文件创建Configuration实例
                    Configuration cfg = new Configuration()
                         .configure();
                    // 以Configuration实例来创建SessionFactory实例
                    ServiceRegistry serviceRegistry = new  StandardServiceRegistryBuilder()
                         .applySettings(cfg.getProperties()).build();
                    sessionFactory =  cfg.buildSessionFactory(serviceRegistry);
               }
               catch (Throwable ex)
               {
                    System.err.println("Initial SessionFactory  creation failed." + ex);
                    throw new ExceptionInInitializerError(ex);
               }
         }
         // ThreadLocal可以隔离多个线程的数据共享，因此不再需要对线程同步
         public static final ThreadLocal<Session> session
               = new ThreadLocal<Session>();
         public static Session currentSession()
               throws HibernateException
         {
               Session s = session.get();
               // 如果该线程还没有Session,则创建一个新的Session
               if (s == null)
               {
                    s = sessionFactory.openSession();
                    // 将获得的Session变量存储在ThreadLocal变量session里
                    session.set(s);
               }
               return s;
         }
         public static void closeSession()
               throws HibernateException
         {
               Session s = session.get();
               if (s != null)
                    s.close();
               session.set(null);
         }
    }

2 测试类

package lee;
    
    import org.hibernate.Transaction;
    import org.hibernate.Session;
    
    import java.util.*;
    import org.crazyit.app.domain.*;
    
    public class PersonManager
    {
        public static void main(String[] args)
        {
            PersonManager mgr = new PersonManager();
            mgr.createAndStorePerson();
            HibernateUtil.sessionFactory.close();
        }
    
    private void createAndStorePerson()
    {
        Session session = HibernateUtil.currentSession();
        Transaction tx = session.beginTransaction();
        // 创建Person对象
        Person wawa = new Person();
        wawa.setAge(21);
        wawa.setName("crazyit.org");
        // 为trainings集合属性添加2个元素
        wawa.getTrainings().add("Wild Java Camp");
        wawa.getTrainings().add("Sun SCJP");
        session.save(wawa);
        Person p = (Person)session.get(Person.class , 1);
        // 再次添加一个集合元素
        p.getTrainings().add("CCNP");
        tx.commit();
        HibernateUtil.closeSession();
    }
    }

**四 测试效果**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70][]

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70 1]: /images/20210724/3ef8e45cbdc747889822e3061cf7d6f8.png