hibernate中关联关系的小结

一对一方案1：
一对一的表现是形式是建立在一对多的基础之上。让外键唯一就可以变成一对一
类的写法：
Users类
public class Users{
    private Long userid;
    private String username;
    //看着是一对多。实质由于外键放已经具备唯一约束，所以set集合中只有一条数据
    private Set<Orders> orderses = new HashSet<Orders>();
}
Orders类：
public class Orders{
    private Long orderid;
    private Double price;
    private Users users;
}
配置文件：
Users配置文件：
<hibernate-mapping>
    <class name="com.puke.domain.Users" table="USERS" schema="PUKE12">
        <id name="userid" type="java.lang.Long">
            <column name="USERID" precision="22" scale="0" />
            <generator class="assigned" />
        </id>
        <property name="username" type="java.lang.String">
            <column name="USERNAME" length="40" />
        </property>
        <!-- set标签的作用：告知Hibernate在当前一方中关联多方的那个集合对象的名字 -->
        <set name="orderses" inverse="true" >
            <!-- key column 告知hibernate表中的外键是谁 -->
            <key>
                <column name="USER_ID" precision="22" scale="0" unique="true" />
            </key>
            <!--
            one-to-many 这个标签的含义：
            1，告知hibernate当前user与order的关系
               2，告知hibernate当前多方的class标签name的值，获取这个class节点中的table属性的值，这样hibernate就知道当前的
               USER_ID位于哪个表中。
               3，告知bibenrate当前set集中放存放什么对象
             -->
            <one-to-many class="com.puke.domain.Orders" />
        </set>
    </class>
</hibernate-mapping>

Orders配置文件：
<hibernate-mapping>
    <class name="com.puke.domain.Orders" table="ORDERS" schema="PUKE12">
        <id name="orderid" type="java.lang.Long">
            <column name="ORDERID" precision="22" scale="0" />
            <generator class="assigned" />
        </id>
        <many-to-one name="users" class="com.puke.domain.Users" fetch="select">
            <column name="USER_ID" precision="22" scale="0" unique="true" />
        </many-to-one>
        <property name="price" type="java.lang.Double">
            <column name="PRICE" precision="6" />
        </property>
    </class>
</hibernate-mapping>

一对一的方案2：
一对一的表现形式就是一对一
Users类：
public class Users{
    private Long userid;
    private String username;
    private Orders orders;
}
Orders类：
public class Orders{
private Long orderid;
    private Double price;
    private Users users;
}
配置文件：
Users配置文件：
<hibernate-mapping>
    <class name="com.puke.domain.Users" table="USERS" schema="PUKE12">
        <id name="userid" type="java.lang.Long">
            <column name="USERID" precision="22" scale="0" />
            <generator class="assigned" />
        </id>
        <property name="username" type="java.lang.String">
            <column name="USERNAME" length="40" />
        </property>
        <!-- set标签的作用：告知Hibernate在当前一方中关联多方的那个集合对象的名字 -->
        <one-to-one name="orders" class="com.puke.domain.Orders"></one-to-one>
    </class>
</hibernate-mapping>

Orders配置文件：
<hibernate-mapping>
    <class name="com.puke.domain.Orders" table="ORDERS" schema="PUKE12">
        <id name="orderid" type="java.lang.Long">
            <column name="ORDERID" precision="22" scale="0" />
            <generator class="assigned" />
        </id>
        <many-to-one name="users" class="com.puke.domain.Users" fetch="select">
            <column name="USER_ID" precision="22" scale="0" unique="true" />
        </many-to-one>
        <property name="price" type="java.lang.Double">
            <column name="PRICE" precision="6" />
        </property>
    </class>
</hibernate-mapping>

一对多：
类的写法：
一方：Users
public class Users{
    private Long id;
    private String username;
    private Set<Orders2> orders2s = new HashSet<Orders2>();
}
多方：Orders
public class Orders{
    private Long id;
    private Double price;
    private Users2 users2;
}

配置文件：
一方的配置文件：
<hibernate-mapping>
    <class name="com.puke.domain2.Users2" table="USERS2" schema="PUKE12">
        <id name="id" type="java.lang.Long">
            <column name="ID" precision="22" scale="0" />
            <generator class="assigned" />
        </id>
        <property name="username" type="java.lang.String">
            <column name="USERNAME" length="40" />
        </property>
        <set name="orders2s" inverse="true">
            <key>
                <column name="USERS_ID" precision="22" scale="0" />
            </key>
            <one-to-many class="com.puke.domain2.Orders2" />
        </set>
    </class>
</hibernate-mapping>

多方配置文件：
<hibernate-mapping>
    <class name="com.puke.domain2.Orders2" table="ORDERS2" schema="PUKE12">
        <id name="id" type="java.lang.Long">
            <column name="ID" precision="22" scale="0" />
            <generator class="assigned" />
        </id>
        <many-to-one name="users2" class="com.puke.domain2.Users2" fetch="select">
            <column name="USERS_ID" precision="22" scale="0" />
        </many-to-one>
        <property name="price" type="java.lang.Double">
            <column name="PRICE" precision="6" />
        </property>
    </class>
</hibernate-mapping>

多对多；