单向双向在数据库中没有区别，但是在java程序中有区别。
在程序中：双向的通过一个就可以找到另一个，单向的通过设置了对应关系的类可以找到它所对应的类，反过来就不行。
注解方式单向主键关联：
和外键一样，只不过注解由@JoinColumn变成@PrimaryKeyJoinColumn
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;
import javax.persistence.PrimaryKeyJoinColumn;
@Entity
public class Husband {
private int id;
private String name;
private Wife wife;
@Id
@GeneratedValue
public int getId() {
return id;
}
public String getName() {
return name;
}
@OneToOne
@PrimaryKeyJoinColumn
public Wife getWife() {
return wife;
}
public void setId(int id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}
public void setWife(Wife wife) {
this.wife = wife;
}
}
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
@Entity
public class Wife {
private int id;
private String name;
@Id
@GeneratedValue
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
xml方式单向主键关联：
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.test.hibernate.StuIdCard">
<id name="id">
<generator class="foreign">
<param name="property">student</param><!-- 根据外键生成该字段 -->
</generator>
</id>
<property name="num"/>
<one-to-one name="student" constrained="true"></one-to-one>
</class>
</hibernate-mapping>
注解方式双向主键关联：
给Wife类追加以下内容
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;
import javax.persistence.PrimaryKeyJoinColumn;
@Entity
public class Wife {
private int id;
private String name;
private Husband husband;
@OneToOne
@PrimaryKeyJoinColumn
public Husband getHusband() {
return husband;
}
public void setHusband(Husband husband) {
this.husband = husband;
}
@Id
@GeneratedValue
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
xml方式主键双向关联：
public class Student {
private int id;
private String name;
private int age;
private String sex;
private boolean good;
private StuIdCard stuIdCard;
public StuIdCard getStuIdCard() {
return stuIdCard;
}
public void setStuIdCard(StuIdCard stuIdCard) {
this.stuIdCard = stuIdCard;
}
public boolean isGood() {
return good;
}
public void setGood(boolean good) {
this.good = good;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
}
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.bjsxt.hibernate.Student" dynamic-update="true">
<id name="id">
<generator class="native"></generator>
</id>
<property name="name"></property>
<property name="age" />
<property name="sex" />
<property name="good" type="yes_no"></property>
<one-to-one name="stuIdCard" property-ref="student"></one-to-one>
</class>
</hibernate-mapping>
