Hibernate实战——关联和连接

分手后的思念是犯贱 2021-07-24 12:41 562阅读 0赞

**一 配置**

<?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"/>
               <mapping class="org.crazyit.app.domain.MyEvent"/>
         </session-factory>
    </hibernate-configuration>

**二 PO**

1 Person

package org.crazyit.app.domain;
    
    import java.util.*;
    
    import javax.persistence.*;
    
    @Entity
    @Table(name = "person_inf")
    public class Person
    {
        // 定义标识属性
        @Id @Column(name = "person_id")
        @GeneratedValue(strategy=GenerationType.IDENTITY)
        private Integer id;
        // 定义Person实例的name成员变量
        private String name;
        // 定义Person实例的age成员变量
        private int age;
        // 定义该Person实体关联的MyEvent实体
        @ManyToOne(targetEntity=MyEvent.class)
        @JoinColumn(name = "event_id" , referencedColumnName="event_id")
        private MyEvent myEvent;
        // 定义一个集合属性
        // 集合属性，保留该对象关联的学校
        @ElementCollection(targetClass=String.class)
        @CollectionTable(name="person_email_inf",
            joinColumns=@JoinColumn(name="person_id" , nullable=false))
        @Column(name="email_detail" , nullable=false)
        private Set<String> emails
            = 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;
        }
    
        // myEvent的setter和getter方法
        public void setMyEvent(MyEvent myEvent)
        {
            this.myEvent = myEvent;
        }
        public MyEvent getMyEvent()
        {
            return this.myEvent;
        }
    
        // emails的setter和getter方法
        public void setEmails(Set<String> emails)
        {
            this.emails = emails;
        }
        public Set<String> getEmails()
        {
            return this.emails;
        }
    
    }

2 MyEvent

package org.crazyit.app.domain;
    
    import java.util.*;
    
    import javax.persistence.*;
    
    @Entity
    @Table(name="event_inf")
    public class MyEvent
    {
        // 定义标识属性
        @Id @Column(name="event_id")
        @GeneratedValue(strategy=GenerationType.IDENTITY)
        private Integer id;
        // 定义事件名称的成员变量
        private String title;
        // 定义事件发生时间的成员变量
        private Date happenDate;
        // 定义该MyEvent实体关联的所有Person实体
        @ManyToMany(targetEntity=Person.class , mappedBy="myEvent")
        private Set<Person> actors
            = new HashSet<>();
    
        // id的setter和getter方法
        public void setId(Integer id)
        {
            this.id = id;
        }
        public Integer getId()
        {
            return this.id;
        }
    
        // title的setter和getter方法
        public void setTitle(String title)
        {
            this.title = title;
        }
        public String getTitle()
        {
            return this.title;
        }
    
        // happenDate的setter和getter方法
        public void setHappenDate(Date happenDate)
        {
            this.happenDate = happenDate;
        }
        public Date getHappenDate()
        {
            return this.happenDate;
        }
    
        // actors的setter和getter方法
        public void setActors(Set<Person> actors)
        {
            this.actors = actors;
        }
        public Set<Person> getActors()
        {
            return this.actors;
        }
    }

**三 测试**

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.text.DateFormat;
    import java.text.SimpleDateFormat;
    
    import java.util.*;
    
    import org.crazyit.app.domain.*;
    
    public class HqlQuery
    {
        public static void main(String[] args)
            throws Exception
        {
            HqlQuery mgr = new HqlQuery();
            // 调用查询方法
            mgr.findPersons();
            // 调用第二个查询方法
            mgr.findPersonsByHappenDate();
            mgr.findPersonsFetchMyEvent();
        }
    
        //c第一个查询方法
        private void findPersons()
        {
            // 获得Hibernate Session
            Session sess = HibernateUtil.currentSession();
            // 开始事务
            Transaction tx = sess.beginTransaction();
            // 以HQL语句创建Query对象,HQL语句使用隐式连接
            List pl = sess.createQuery("from Person p where p.myEvent.title > :title")
                // 执行setString()方法为HQL语句的参数赋值
                .setString("title", " ")
                //Query调用list()方法访问查询的全部实例
                .list();
            // 遍历查询的全部结果
            for (Object ele : pl)
            {
                Person p = (Person)ele;
                System.out.println(p.getName());
            }
            // 提交事务
            tx.commit();
            HibernateUtil.closeSession();
        }
        // 第二个查询方法
        private void findPersonsByHappenDate()throws Exception
        {
            // 获得Hibernate Session对象
            Session sess = HibernateUtil.currentSession();
            Transaction tx = sess.beginTransaction();
            System.out.println("====第二个查询：开始通过日期查找人====");
            // 以HQL语句创建Query对象,HQL语句使用显式连接
            // 因为没有使用fetch关键字，所以返回List集合元素是被查询实体
            List pl = sess.createQuery("select p from Person p left join "
                + "p.myEvent event where event.happenDate < :endDate")
                .setDate("endDate",new Date())
                .list();
            // 遍历结果集
            for (Object ele : pl)
            {
                Person p = (Person)ele;
                System.out.println(p.getName());
                // 因为执行HQL时没有使用fetch，
                // 所以只能在Session没有关闭时访问Person关联实体的属性
                System.out.println(p.getMyEvent().getTitle());
            }
            tx.commit();
            HibernateUtil.closeSession();
        }
    
        // 第三个查询方法，测试fetch关键字
        private void findPersonsFetchMyEvent()throws Exception
        {
            // 获得Hibernate Session对象
            Session sess = HibernateUtil.currentSession();
            Transaction tx = sess.beginTransaction();
            System.out.println("====第三个查询：测试fetch查询====");
            // 以HQL语句创建Query对象,HQL语句使用显式连接
            // 因为使用了fetch关键字，所以返回结果中已有包含关联实体
            List pl = sess.createQuery("from Person p left join fetch "
                + "p.myEvent event where event.happenDate < :endDate")
                .setDate("endDate",new Date())
                .list();
            tx.commit();
            HibernateUtil.closeSession();
            // 遍历结果集
            for (Object ele : pl)
            {
                Person p = (Person)ele;
                System.out.println(p.getName());
                // 因为HQL语句中使用了fecth关键字
                // 所以可以在Session关闭后访问Person关联实体的属性
                System.out.println(p.getMyEvent().getTitle());
            }
        }
    }

**四 数据库脚本**

drop database if exists hibernate;
    
    create database hibernate;
    
    use hibernate;
    
    CREATE TABLE event_inf (
      event_id int(11) NOT NULL auto_increment,
      happenDate date default NULL,
      title varchar(255) default NULL,
      PRIMARY KEY  (event_id)
    );
    
    INSERT INTO event_inf VALUES
    (1,'2004-10-03','很高兴的事情'),
    (2,'2005-10-03','很普通的事情'),
    (3,'2004-10-04','疯狂Java筹备中'),
    (4,'2005-10-05','疯狂Java开始培训');
    
    CREATE TABLE person_inf (
      person_id int(11) NOT NULL auto_increment,
      name varchar(255) default NULL,
      age int(11) default NULL,
      event_id int(11),
      PRIMARY KEY (person_id),
      FOREIGN KEY (event_id) REFERENCES event_inf(event_id)
    );
    
    
    INSERT INTO person_inf VALUES
    (1,'crazyit.org',30 , 1),
    (2,'老朱',30 , 1);
    
    
    CREATE TABLE person_email (
      person_id int(11) NOT NULL,
      email varchar(255) default NULL,
      KEY FKECD3B632CC53FFDC (person_id),
      FOREIGN KEY (person_id) REFERENCES person_inf (person_id)
    );
    
    INSERT INTO person_email VALUES
    (1,'crazyit@crazyit.org'),
    (1,'crazyit@fkit.com'),
    (2,'dddd@163.com'),
    (2,'vvvvvv@163.com');

**五 测试**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70][]

Hibernate:
        select
            person0_.person_id as person_i1_2_,
            person0_.age as age2_2_,
            person0_.event_id as event_id4_2_,
            person0_.name as name3_2_
        from
            person_inf person0_ cross
        join
            event_inf myevent1_
        where
            person0_.event_id=myevent1_.event_id
            and myevent1_.title>?
    Hibernate:
        select
            myevent0_.event_id as event_id1_0_0_,
            myevent0_.happenDate as happenDa2_0_0_,
            myevent0_.title as title3_0_0_
        from
            event_inf myevent0_
        where
            myevent0_.event_id=?
    crazyit.org
    老朱
    ====第二个查询：开始通过日期查找人====
    Hibernate:
        select
            person0_.person_id as person_i1_2_,
            person0_.age as age2_2_,
            person0_.event_id as event_id4_2_,
            person0_.name as name3_2_
        from
            person_inf person0_
        left outer join
            event_inf myevent1_
                on person0_.event_id=myevent1_.event_id
        where
            myevent1_.happenDate<?
    Hibernate:
        select
            myevent0_.event_id as event_id1_0_0_,
            myevent0_.happenDate as happenDa2_0_0_,
            myevent0_.title as title3_0_0_
        from
            event_inf myevent0_
        where
            myevent0_.event_id=?
    crazyit.org
    很高兴的事情
    老朱
    很高兴的事情
    ====第三个查询：测试fetch查询====
    Hibernate:
        select
            person0_.person_id as person_i1_2_0_,
            myevent1_.event_id as event_id1_0_1_,
            person0_.age as age2_2_0_,
            person0_.event_id as event_id4_2_0_,
            person0_.name as name3_2_0_,
            myevent1_.happenDate as happenDa2_0_1_,
            myevent1_.title as title3_0_1_
        from
            person_inf person0_
        left outer join
            event_inf myevent1_
                on person0_.event_id=myevent1_.event_id
        where
            myevent1_.happenDate<?
    crazyit.org
    很高兴的事情
    老朱
    很高兴的事情

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