【Hibernate】--一对一关联、联合主键

一、数据模型

1.学生信息模型（编号、名称、身份信息）

public class Student implements java.io.Serializable{

	private static final long serialVersionUID = 1L;

	private Integer sid;

	private String sname;

	private IdClass pid;

	public Integer getSid() {
		return sid;
	}

	public void setSid(Integer sid) {
		this.sid = sid;
	}

	public String getSname() {
		return sname;
	}

	public void setSname(String sname) {
		this.sname = sname;
	}

	public IdClass getPid() {
		return pid;
	}

	public void setPid(IdClass pid) {
		this.pid = pid;
	}
}

2.身份信息模型（身份ID、省份）

public class IdClass implements java.io.Serializable{

	private static final long serialVersionUID = 1L;

	private String pid;

	private String provience;

	private Student stu;

	public String getPid() {
		return pid;
	}

	public void setPid(String pid) {
		this.pid = pid;
	}

	public String getProvience() {
		return provience;
	}

	public void setProvience(String provience) {
		this.provience = provience;
	}

	public Student getStu() {
		return stu;
	}

	public void setStu(Student stu) {
		this.stu = stu;
	}
}

二、单向唯一关联

A.配置文件描述

<hibernate-mapping package="com.hibernate.orm">
    <class name="Student" table="student">
        <id name="sid" type="java.lang.Integer" length="50">
            <generator class="identity"/>
        </id>
        <property name="sname" column="s_name" not-null="false" type="java.lang.String"/>

       <!-- 主控方：这里虽然使用了many2one,但是设置了unique为true，这样就只能是单向一对一关联了 -->
       <many-to-one name="pid" column="pid" cascade="all" unique="true"/>
    </class>
</hibernate-mapping>

<hibernate-mapping package="com.hibernate.orm">
    <class name="IdClass" table="id_class_info">
        <id name="pid" type="java.lang.String" length="20">
            <generator class="assigned"/>
        </id>
        <property name="provience" column="provience" not-null="false" type="java.lang.String"/>

        <!-- 被控方：指定stu属性被IdClass中的pid属性控制 -->
       	<one-to-one name="stu" property-ref="pid"/>

    </class>
</hibernate-mapping>

B.注解描述（在相关的属性上添加注解描述）

@Entity
@Table(name="student",catalog="study")
public class Student implements java.io.Serializable{

	private static final long serialVersionUID = 1L;

	@Id
	@GeneratedValue(strategy=GenerationType.IDENTITY)
	private Integer sid;

	@Column(name="s_name",nullable=false, length=11)
	private String sname;

	@OneToOne(cascade=CascadeType.ALL)
	@JoinColumn(name="pid", nullable=false, unique=true)
	private IdClass pid;

	//......getter和setter方法省略............
}

@Entity
@Table(name="id_class_info",catalog="study")
public class IdClass implements java.io.Serializable{

	private static final long serialVersionUID = 1L;

	@Id
	@GeneratedValue(generator="pid")
	@GenericGenerator(name="pid",strategy="assigned")
	private String pid;

	@Column(name="provience", length=40, nullable=false)
	private String provience;

	//只要是双向关联就一定要指定mappedBy,将控制权交给指定的一方
	@OneToOne(mappedBy="pid")
	private Student stu;

	//......getter和setter方法省略............
}

注：一对一关联配置参见网友博客：http://blog.csdn.net/dreamcatchergo/article/details/13627709

三、双向一对一外键关联

                 单向的基础上，添加另一方为被控方，通过one-to-one实现被控方描述

A.配置文件描述

<!-- 被控方：指定stu属性被IdClass中的pid属性控制 -->
<one-to-one name="stu" property-ref="pid"/>

B.注解描述

//只要是双向关联就一定要指定mappedBy,将控制权交给指定的一方
@OneToOne(mappedBy="pid")
private Student stu;

四、联合主键

                添加主键类，在身份信息模型中添加血型，将身份ID和血型作为联合主键，代码如下

public class IdCardPK implements Serializable{

	private static final long serialVersionUID = 1L;

	private String pid;

	private String bloodType; //血型

	//*******************

}

A.配置文件描述

<hibernate-mapping package="com.hibernate.orm.ufk">
    <class name="IdClass" table="id_class_info">
        <!-- 联合主键 -->
       	<composite-id name="idCardPK" class="com.hibernate.orm.ufk.IdCardPK">
       		<key-property name="pid" column="p_id" length="20" type="string"/>
       		<key-property name="bloodType" column="blood_type" length="10" type="string"/>

       		<!-- 不能再指定 generator
       		<generator class="assigned"/>
       		-->
       	</composite-id>

       	<property name="provience" column="provience" not-null="false" type="string"/>
    </class>
</hibernate-mapping>

student方修改关联配置，将原有的pid做如下修改：

<many-to-one name="pid" cascade="all">
	<column name="p_id" unique="true"/>
	<column name="blood_type"/>
</many-to-one>

B.注解描述

主键类配置如下，注意添加getter和setter方法：

@Embeddable
public class IdCardPK implements Serializable{

	private static final long serialVersionUID = 1L;

	@Column(name="p_id",nullable=false, length=20)
	private String pid;

	@Column(name="blood_type",nullable=false)
	private String bloodType; //血型

}

身份信息修改如下

@EmbeddedId
private IdCardPK idCardPK;

学生信息模型关联身份信息配置：

@OneToOne(cascade=CascadeType.ALL)
@JoinColumns({
	@JoinColumn(name="p_id",referencedColumnName="p_id"),
	@JoinColumn(name="blood_type",referencedColumnName="blood_type")
})
private IdClass pid;

五、组件关联（将POJO类中的属性作为添加到某实体类）

              定义一个组件类POJO，代码如下：

public class IdClass{

	private String provience;

	private String bloodType;

	public String getProvience() {
		return provience;
	}

	public void setProvience(String provience) {
		this.provience = provience;
	}

	public String getBloodType() {
		return bloodType;
	}

	public void setBloodType(String bloodType) {
		this.bloodType = bloodType;
	}
}

A.配置文件描述

                      将POJO中的属性作为student的属性，配置如下：

<hibernate-mapping package="com.hibernate.orm.component">
    <class name="Student" table="student">
        <id name="sid" type="integer" length="50">
            <generator class="identity"/>
        </id>
        <property name="sname" column="s_name" not-null="false" type="string"/>

       <!-- 组件关联配置 -->
       <component name="pid" class="IdClass">
       		<property name="provience" column="provience" length="20"/>
       		<property name="bloodType" column="blood_type" length="10"></property>
       </component>
    </class>
</hibernate-mapping>

B.注解描述，通过Embedded关联组件

//和组件关联
@Embedded
private IdClass pid;