[Hibernate] - Annotations - One To One

Hibernate annotation 一对一的两种实现：

1）幅表中有主表的主键ID做为引用

2）幅表的主键即为主表的ID

---

hibernate.cfg.xml

<?xml version="1.0" encoding="UTF-8"?>
<!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>

        <!-- Database connection settings -->
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://127.0.0.1/testdb</property>
        <property name="connection.username">root</property>
        <property name="connection.password"></property>

        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">1</property>

        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>

        <!-- Enable Hibernate's automatic session context management -->
        <property name="current_session_context_class">thread</property>

        <!-- Disable the second-level cache  -->
        <property name="cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</property>

        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>

        <!-- Drop and re-create the database schema on startup -->
        <property name="hbm2ddl.auto">update</property>

        <mapping class="com.my.bean.User"/>
        <mapping class="com.my.bean.UserCard"/>
        <mapping class="com.my.bean.UserInfo"/>

    </session-factory>

</hibernate-configuration>

HibernateUtil.java

package com.my.dao.util;

import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {

    private static final SessionFactory sessionFactory = buildSessionFactory();

    private static SessionFactory buildSessionFactory() {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            Configuration configuration = new Configuration();
            return configuration.configure().buildSessionFactory(
                    new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build());
        } catch (Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }

}

Java Beans:

package com.my.bean;

import java.util.Date;

import javax.persistence.*;

@Entity
@Table(name="user")
public class User {
    @Id @GeneratedValue @Column(name="user_id", nullable=false)
    private long userID;

    @Column(name="user_name", length=100, nullable=false)
    private String userName;

    @Column(name="create_time", nullable=false)
    private Date createTime;

    @OneToOne(mappedBy="user")
    private UserCard userCard;

    @OneToOne(cascade=CascadeType.ALL)
    @PrimaryKeyJoinColumn
    private UserInfo userInfo;

    public long getUserID() {
        return userID;
    }

    public void setUserID(long userID) {
        this.userID = userID;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public Date getCreateTime() {
        return createTime;
    }

    public void setCreateTime(Date createTime) {
        this.createTime = createTime;
    }

    public UserCard getUserCard() {
        return userCard;
    }

    public void setUserCard(UserCard userCard) {
        this.userCard = userCard;
    }
}

package com.my.bean;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;
import javax.persistence.Table;

@Entity
@Table(name="user_card")
public class UserCard {
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="card_id", nullable=false)
    private long cardID;

    @OneToOne
    @JoinColumn(name="user_id")
    private User user;

    @Column(name="card_name", nullable=false)
    private String cardName;

    public long getCardID() {
        return cardID;
    }
    public void setCardID(long cardID) {
        this.cardID = cardID;
    }
    public User getUser() {
        return user;
    }
    public void setUser(User user) {
        this.user = user;
    }
    public String getCardName() {
        return cardName;
    }
    public void setCardName(String cardName) {
        this.cardName = cardName;
    }
}

package com.my.bean;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.Table;

import org.hibernate.annotations.GenericGenerator;
import org.hibernate.annotations.Parameter;

@Entity
@Table(name="user_info")
public class UserInfo {
    @Id
    @GeneratedValue(generator="userInfoForeignKey")
    @GenericGenerator(name="userInfoForeignKey", strategy="foreign", parameters=@Parameter(name="property", value="user"))
    @Column(name="user_id", nullable=false)
    private long userID;

    @Column(name="message", nullable=false)
    private String Message;

    @OneToOne(mappedBy="userInfo")
    private User user;

    public long getUserID() {
        return userID;
    }

    public void setUserID(long userID) {
        this.userID = userID;
    }

    public String getMessage() {
        return Message;
    }

    public void setMessage(String message) {
        Message = message;
    }

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }
}

测试：

package com.my.init;
import java.util.Date;

import org.hibernate.Session;
import org.hibernate.Transaction;

import com.my.bean.User;
import com.my.bean.UserCard;
import com.my.bean.UserInfo;
import com.my.dao.util.HibernateUtil;

public class Test {

    public static void main(String[] args) {
        Session session = HibernateUtil.getSessionFactory().openSession();
        Transaction tx = session.beginTransaction();

        try {
            //---------------------------------------------------------
            // The first method
            //---------------------------------------------------------
            // add user
            User user = new User();
            user.setUserName("Robin");
            user.setCreateTime(new Date());

            // add user card
            UserCard userCard = new UserCard();
            userCard.setCardName("BBC");

            // add user card to user object
            user.setUserCard(userCard);
            userCard.setUser(user);

            //---------------------------------------------------------
            // The second method
            //---------------------------------------------------------
            UserInfo userInfo = new UserInfo();
            userInfo.setMessage("Message");
            userInfo.setUser(user);

            //---------------------------------------------------------
            // save
            //---------------------------------------------------------
            session.save(user);
            session.save(userCard);
            session.save(userInfo);

            tx.commit();
        } catch (Exception e) {
            tx.rollback();
            e.printStackTrace();
        }

        session.close();
    }

}