Hibernate5.2之一对一外键关联(五)

                                                 Hibernate5.2之一对一外键关联(五)

一.简介

　　上篇文章中笔者介绍了Hibernate关联关系中的一对一外键关联，本篇博客将介绍一对一外键关联。其实我们回过头想一想，外键关联其实就是一对多关联关系中将多的一方简化为一个，就是我们本文所要介绍的一对一的外键关联。

二.外键关联

2.1数据库表的创建

create table people (
    id varchar2(255 char) not null,
    name varchar2(255 char),
    sex varchar2(255 char),
    primary key (id)
);

create table cards (
    id varchar2(255 char) not null,
    card_num varchar2(255 char),
    people_id varchar2(255 char),
    primary key (id)
);

2.2 hbm文件的方式

public class People {
    private String id;
    private String name;
    private String sex;
    private IdCard idCard;

    //setter and getter
}

public class IdCard {
    private String id;
    private String cardNum;
    private People people;

    //setter and getter
}

People.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
    <class name="com.demo.hibernate.one2one.People" table="people">
        <id name="id" type="string">
            <generator class="uuid"></generator>
        </id>

        <property name="name" type="string" column="name"></property>
        <property name="sex" type="string" column="sex"></property>

        <one-to-one name="idCard" class="com.demo.hibernate.one2one.IdCard" cascade="all" property-ref="people"></one-to-one>
    </class>
</hibernate-mapping>

IdCard.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
    <class name="com.demo.hibernate.one2one.IdCard" table="cards">
        <id name="id" type="string" column="id">
            <generator class="uuid"></generator>
        </id>

        <property name="cardNum" type="string" column="card_num"></property>
        <many-to-one name="people" class="com.demo.hibernate.one2one.People" column="people_id" unique="true"></many-to-one>
    </class>
</hibernate-mapping>

2.3 注解的方式

People.java

@Entity
@Table(name="people")
public class People {

    @Id
    @Column(name="id")
    @GenericGenerator(name="uuidGenerator", strategy="uuid")
    @GeneratedValue(generator="uuidGenerator")
    private String id;

    @Column(name="name")
    private String name;

    @Column(name="sex")
    private String sex;

    @OneToOne(cascade={CascadeType.ALL}, fetch=FetchType.LAZY, mappedBy="people")
    private IdCard idCard;

    //setter and getter
}

IdCard.java

@Entity
@Table(name="cards")
public class IdCard {

    @Id
    @Column(name="id")
    @GenericGenerator(name="uuidGenerator", strategy="uuid")
    @GeneratedValue(generator="uuidGenerator")
    private String id;

    @Column(name="card_num")
    private String cardNum;

    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name="people_id")
    private People people;

    //setter and getter
}

2.4 代码测试

A.保存

@Test
public void save(){
    Transaction tx = session.beginTransaction();
    People people = new People();
    people.setName("AAA");
    people.setSex("男");

    IdCard idCard = new IdCard();
    idCard.setCardNum("889900");
    idCard.setPeople(people);

    people.setIdCard(idCard);
    session.save(people);

    tx.commit();
}

B.get

@Test
public void get(){
    People people = session.get(People.class, "402882e6564a70fa01564a70fbd40000");
    System.out.println("此时已经发送了SQL语句");
    System.out.println(people.getName() + "::" + people.getSex());
    IdCard idCard = people.getIdCard();
    System.out.println(idCard.getCardNum());
}

C.load

@Test
public void load(){
    People people = session.load(People.class, "402882e6564a70fa01564a70fbd40000");
    System.out.println("此时没有发送任何的SQL语句");
    System.out.println(people.getName() + "::" + people.getSex());
    System.out.println("=============");
    IdCard idCard = people.getIdCard();
    System.out.println(idCard.getCardNum());
}

D.delete

@Test
public void delete(){
    People people = new People();
    people.setId("402882e6564a7c1501564a7c16d80000");

    IdCard card = new IdCard();
    card.setId("402882e6564a7c1501564a7c16e50001");

    people.setIdCard(card);
    Transaction tx = session.beginTransaction();
    session.delete(people);
    tx.commit();
}

E.update

@Test
public void update(){
    Transaction tx = session.beginTransaction();
    People people = new People();
    people.setId("402882e6564a70fa01564a70fbd40000");
    people.setName("YYYY");
    people.setSex("男");
    session.update(people);
    tx.commit();
}