Hibernate5.2之一对一主键关联(四)

一.简介

　　一对一关联关系分为两种：a.主键关联；b.外键关联。这两种关联关系在日常的开发中都比较的常用，本篇文章介绍主键关联，在下一篇文章中介绍外键关联。

二.主键关联

2.1 数据库的创建

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

IdCard.hbm.xml

     
         
              
                   
                        
         people            
                
                   
               
           
      
     

2.3 注解的方式

IdCard.java

@Entity@Table(name="cards")public class IdCard {        @Id    @Column(name="id")    @GenericGenerator(name="foreignGenerator", strategy="foreign", parameters={@Parameter(value="people", name="property")})    @GeneratedValue(generator="foreignGenerator")    private String id;        @Column(name="card_num")    private String cardNum;        /**     * mappedBy="idCard",其中idCard为People类中的属性名     */    @OneToOne(mappedBy="idCard", fetch=FetchType.LAZY)    private People people;}

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;        /**     * cascade表示级联的意思     * FetchMode.SELECT的方式表示，查询与之关联的数据的时候，使用select的方式，而不是左外连接,与在     * 在@OneToOne()中间加上fetch=FetchType.LAZY所表达出来的意思是一样的。     * @PrimaryKeyJoinColumn必须在生产主键的一方指定，不然会在被关联的一方多出一列     */    @OneToOne(cascade=CascadeType.ALL)    @Fetch(value=FetchMode.SELECT)      @PrimaryKeyJoinColumn       private IdCard idCard;}

2.4 代码测试

A.保存

@Testpublic 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.load

@Testpublic void load(){    People people = session.load(People.class, "402882e65649c101015649c1031e0000");    System.out.println("此时没有发送任何的SQL语句");    System.out.println(people.getName() + "::" + people.getSex());    IdCard idCard = people.getIdCard();    System.out.println(idCard.getCardNum());}

C.get

@Testpublic void get(){    People people = session.get(People.class, "402882e65649c101015649c1031e0000");    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());}

D.update

@Testpublic void update(){    Transaction tx = session.beginTransaction();    People people = new People();    people.setId("402882e65649c92e015649c92fd90000");    people.setName("HHHNNN");    people.setSex("女");    session.update(people);    tx.commit();}

E.delete

@Testpublic void delete(){    People people = new People();    people.setId("402882e65649c101015649c1031e0000");            IdCard card = new IdCard();    card.setId("402882e65649c101015649c1031e0000");            people.setIdCard(card);    Transaction tx = session.beginTransaction();    session.delete(people);    tx.commit();}