Hibernate 关联映射个人略述

单向多对一关联：只有在一边配置关联映射。。而另外一边不管。。

            案例(一个父亲拥有多个孩子)

父亲类

 

public class Father implements Serializable {

	
	private static final long serialVersionUID = -8390304441273897145L;

	public Father(){
		
	}
	//父亲ID
	private Integer fatherId;
	//父亲姓名
	private String fatherName;

	public Integer getFatherId() {
		return fatherId;
	}

	public void setFatherId(Integer fatherId) {
		this.fatherId = fatherId;
	}

	public String getFatherName() {
		return fatherName;
	}

	public void setFatherName(String fatherName) {
		this.fatherName = fatherName;
	}
}

一方： 配置关联映射

<hibernate-mapping package="net.jsp.orm">
	<class name="Father" table="FATHER">
		<id name="fatherId" column="FATHERID" type="java.lang.Integer">
			<generator class="identity" />
		</id>
		
		<property name="fatherName" column="FATHERNAME" type="java.lang.String" />
	</class>
</hibernate-mapping>

 

孩子类

public class Child implements Serializable {

	private static final long serialVersionUID = 6750561728903621833L;
	
	public Child(){
		
	}
	private Integer childId;
	
	private String childName;
	//多对一
	private Father father;

	public Integer getChildId() {
		return childId;
	}

	public void setChildId(Integer childId) {
		this.childId = childId;
	}

	public String getChildName() {
		return childName;
	}

	public void setChildName(String childName) {
		this.childName = childName;
	}

	public Father getFather() {
		return father;
	}

	public void setFather(Father father) {
		this.father = father;
	}
}

 多方：配置关联映射

<hibernate-mapping package="net.jsp.orm">
	<class name="Child" table="CHILD">
		<id name="childId" column="CHILDID">
			<generator class="identity" />
		</id>
		
		<property name="childName" column="CHILDNAME" />
		<!-- 多方的配置   -->
		<many-to-one name="father" class="Father" column="FATHERID" />
	</class>
</hibernate-mapping>

 双向多对一关联：即在父亲类也添加一个孩子对象。。那么概念即(一个孩子或许有多个父亲[养父...]) 。配置如同上面的多方配置关联。。。。

 

 

单向一对多关联：

         如同上代码。。将 Child的 Father 对象去掉。 然后再Father  类中添加 set<Child> childs属性 即可。一方配置关联映射如下：

<hibernate-mapping package="net.jsp.orm">
	<class name="Father" table="FATHER">
		<id name="fatherId" column="FATHERID" type="java.lang.Integer">
			<generator class="identity" />
		</id>
		
		<property name="fatherName" column="FATHERNAME" type="java.lang.String" />
		<set name="childs" >
			<key column="fatherId" />
			<one-to-many class="Child"/>
		</set>
	</class>
</hibernate-mapping>

 

双向一对多。就组成了。多对多的关联。。。

 

 

多对多关联 时。应当数据库有个中间关联表  比如用户表跟信息表。。一个用户可以发多条信息 ，一条信息可以响应给多个用户。。这样如果有张中间表就更直观一些。。。

 

 

<!-- 用户方的关联配置 -->
<hibernate-mapping>
<class name="net.jsp.orm.User" table="[USER]">
	<id name="uid" column="UID">
	<generator class="identity" />
	</id>
	<property name="uname" column="UNAME" type="string"
		not-null="true" length="50"
	/>
	<property name="upass" type="string">
		<column name="UPASS" not-null="true" length="50" />
	</property>
	<set name="messages" table="TEMP_USER_MSG">
		<key column="TEMP_USERID" />
		<many-to-many class="net.jsp.orm.Message" column="TEMP_MSGID" />
	</set>
                ..............
</class>
</hibernate-mapping>

 

<!-- 消息方的关联配置 -->
<hibernate-mapping>
<class name="net.jsp.orm.Message" table="[Message]">
	<id name="msgId" column="MSGID">
	<generator class="identity" />
	</id>
	<property name="msgContent" column="MSGCONTENT" type="string"
		not-null="true" 
	/>
    <set name="users" table="TEMP_USER_MSG">
		<key column="TEMP_USERID" />
		<many-to-many class="net.jsp.orm.User" column="TEMP_MSGID" />
	</set>
               ........
</class>
</hibernate-mapping>