hibernate之关系映射上

分别创建user,farm,user_general三张表

create table user(
 uuid bigint not null auto_increment,
 name varchar(100),
 age int not null,
 province varchar(100),
 city varchar(100),
 street varchar(100),
 constraint pk_user primary key(uuid)
)charset=utf8 ENGINE=InnoDB;

create table user_general(
uuid bigint not null,
realname varchar(10),
gender varchar(10),
birthday int,
height int,
weight int,
 constraint pk_user_general primary key(uuid),
 constraint fk_user_general foreign key(uuid) references user(uuid))charset=utf8 ENGINE=InnoDB;

create table farm(
uuid bigint not null auto_increment,
user_id bigint,
name varchar(10),
constraint pk_farm primary key(uuid),
constraint fk_farm foreign key(user_id) references user(uuid))charset=utf8 ENGINE=InnoDB;

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单向关联：

1.多对一映射(many to one)：

该标签在持久化类中属于多的一方配置；例如本例中farm即为多的一方。

重点是这段配置:

<many-to-one name="user" class="org.hibernate.tutorials.domain.User" column="user_id" cascade="save-update"/>

其中column对应表中的外键(另一张表的主键)，cascade设置为save-update后即可实现向数据库中级联修改

farm.hbm.xml配置:

1 <hibernate-mapping>
2     <class name="org.hibernate.tutorials.domain.Farm" table="farm">
3         <id name="uuid">
4             <generator class="native"/>
5         </id>
6         <property name="name"/>
7         <many-to-one name="user" class="org.hibernate.tutorials.domain.User" column="user_id" cascade="save-update"/>
8     </class>
9 </hibernate-mapping>

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Farm对应的实体类:　

public class Farm implements Serializable{
    
    private int uuid;
    
    private String name;
    
    private User user;//农场所属用户

    /**
     * @return the uuid
     */
    public int getUuid() {
        return uuid;
    }

    /**
     * @param uuid the uuid to set
     */
    public void setUuid(int uuid) {
        this.uuid = uuid;
    }

    /**
     * @return the name
     */
    public String getName() {
        return name;
    }

    /**
     * @param name the name to set
     */
    public void setName(String name) {
        this.name = name;
    }

    /**
     * @return the user
     */
    public User getUser() {
        return user;
    }

    /**
     * @param user the user to set
     */
    public void setUser(User user) {
        this.user = user;
    }

    /* (non-Javadoc)
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        return "Farm [uuid=" + uuid + ", name=" + name + "]";
    }

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测试代码:

 1     Session session = HibernateUtil.getSessionFactory().getCurrentSession();
 2         
 3         User user = new User();
 4         user.setName("lucy");
 5         
 6         Farm farm=new Farm();
 7         farm.setName("test3");
 8         farm.setUser(user);
 9         
10         Farm farm1=new Farm();
11         farm1.setName("test4");
12         farm1.setUser(user);
13         
14         session.beginTransaction();
15         session.save(farm);
16         session.save(farm1);
17         session.getTransaction().commit();

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2.一对一映射(分为2种情况：唯一外键和主键关联)

2.1：唯一外键：用的标签仍为many-to-one 区别是需要加unique="true"属性表示唯一映射，具体案例看这里

2.2主键关联映射:(一个字段同时是主键和外键(user和user_general))

<one-to-one name="user" class="org.hibernate.tutorials.domain.User" constrained="true"/> constrained="true"指明该类(UserGeneral)和关联的类(User)对应的表，通过外键引用对主键约束

UserGeneral.hbm.xml 配置

 1 <hibernate-mapping>
 2     <class name="org.hibernate.tutorials.domain.UserGeneral" table="user_general">
 3         <id name="uuid">
 4             <generator class="foreign">
 5                 <param name="property">user</param>
 6             </generator>
 7         </id>
 8         <property name="realname"/>
 9         <one-to-one name="user" class="org.hibernate.tutorials.domain.User" constrained="true"/>
10     </class>    
11 </hibernate-mapping>

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测试代码:

 1     Session session = HibernateUtil.getSessionFactory().getCurrentSession();
 2         
 3         User user = new User();
 4         user.setName("rrrrr");
 5         
 6         UserGeneral ge=new UserGeneral();
 7         ge.setUser(user);
 8         ge.setRealname("cccccc");
 9         
10         session.beginTransaction();
11         session.save(ge);
12         session.getTransaction().commit();

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参考：http://blog.csdn.net/zhang_xinxiu/article/details/25864763，http://blog.csdn.net/zhang_xinxiu/article/details/25950451

http://jinnianshilongnian.iteye.com/blog/1522591