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;

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:

 <hibernate-mapping>
     <class name="org.hibernate.tutorials.domain.Farm" table="farm">
         <id name="uuid">
             <generator class="native"/>
         </id>
         <property name="name"/>
         <many-to-one name="user" class="org.hibernate.tutorials.domain.User" column="user_id" cascade="save-update"/>
     </class>
 </hibernate-mapping>

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 + "]";
    }
    

测试代码:

     Session session = HibernateUtil.getSessionFactory().getCurrentSession();

         User user = new User();
         user.setName("lucy");

         Farm farm=new Farm();
         farm.setName("test3");
         farm.setUser(user);

         Farm farm1=new Farm();
         farm1.setName("test4");
         farm1.setUser(user);

         session.beginTransaction();
         session.save(farm);
         session.save(farm1);
         session.getTransaction().commit();

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

 <hibernate-mapping>
     <class name="org.hibernate.tutorials.domain.UserGeneral" table="user_general">
         <id name="uuid">
             <generator class="foreign">
                 <param name="property">user</param>
             </generator>
         </id>
         <property name="realname"/>
         <one-to-one name="user" class="org.hibernate.tutorials.domain.User" constrained="true"/>
     </class>
 </hibernate-mapping> 

测试代码:

     Session session = HibernateUtil.getSessionFactory().getCurrentSession();

         User user = new User();
         user.setName("rrrrr");

         UserGeneral ge=new UserGeneral();
         ge.setUser(user);
         ge.setRealname("cccccc");

         session.beginTransaction();
         session.save(ge);
         session.getTransaction().commit();

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