Hibernate实战——Set集合属性

逃离我推掉我的手 2021-07-24 16:26 490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.Set;
    import java.util.HashSet;
    import javax.persistence.*;
    
    @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;
        // 集合属性，保留该对象关联的学校
        @ElementCollection(targetClass=String.class)
        // 映射保存集合属性的表
        @CollectionTable(name="school_inf", // 指定表名为school_inf
            joinColumns=@JoinColumn(name="person_id" , nullable=false))
        // 指定保存集合元素的列为 school_name，nullable=false增加非空约束
        @Column(name="school_name" , nullable=false)
        private Set<String> schools
            = new HashSet<>();
    
        // 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;
        }
    
        // schools的setter和getter方法
        public void setSchools(Set<String> schools)
        {
            this.schools = schools;
        }
        public Set<String> getSchools()
        {
            return this.schools;
        }
    
    }

**三 测试代码**

1 工具类

package lee;
    
    import org.hibernate.*;
    import org.hibernate.service.*;
    import org.hibernate.boot.registry.*;
    import org.hibernate.cfg.*;
    
    
    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

package lee;
    
    import org.hibernate.Transaction;
    import org.hibernate.Session;
    
    import java.util.Date;
    import java.util.Set;
    import java.util.HashSet;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 person = new Person();
            person.setAge(20);
            person.setName("crazyit.org");
            // 向person的schools集合属性中添加两个字符串元素
            person.getSchools().add("小学");
            person.getSchools().add("中学");
            session.save(person);
            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/20210724/8524550687424100acf5df6286b36cdc.png