一、概述
我们以Company与Address类为例，介绍映射一对一关联关系的方法。
一对一的关联方法有两种
-按照外键映射：两个表任意一个表定义一个外键，来关联另一个表。
-按照主键映射：一个表的主键同时作为外键，和另一个表的主键保持一致。
二、按照外键映射
（1）创建实体类
???????????public class Company { ???????????????private Integer id; ???????????????private String name; ???????????????private Address address; ???????????????public Integer getId() { ???????????????????return id; ???????????????} ???????????????public void setId(Integer id) { ???????????????????this.id = id; ???????????????} ???????????????public String getName() { ???????????????????return name; ???????????????} ???????????????public void setName(String name) { ???????????????????this.name = name; ???????????????} ???????????????public Address getAddress() { ???????????????????return address; ???????????????} ???????????????public void setAddress(Address address) { ???????????????????this.address = address; ???????????????} ???????????} ????????????public class Address { ???????????????private Integer id; ???????????????private String name; ???????????????private Company company; ???????????????public Integer getId() { ???????????????????return id; ???????????????} ???????????????public void setId(Integer id) { ???????????????????this.id = id; ???????????????} ???????????????public String getName() { ???????????????????return name; ???????????????} ???????????????public void setName(String name) { ???????????????????this.name = name; ???????????????} ???????????????public Company getCompany() { ???????????????????return company; ???????????????} ???????????????public void setCompany(Company company) { ???????????????????this.company = company; ???????????????} ???????????} （2）我们配置映射文件，我们在Company这一方设置外键来关联Address 有外键的一方要使用<many-to-one>元素来配置。
???????Company.hbm.xml ????????<hibernate-mapping > ???????????<class name="com.cad.domain.Company" table="company"> ???????????????<id name="id" column="id"> ???????????????????<generator class="native"></generator> ???????????????</id> ???????????????<property name="name" column="name"></property> ????????????????<!--column指定外键，unique指定外键唯一约束，设为true，就可以表达Company和Address对象之间的一对一关联--> ???????????????<many-to-one name="address" class="com.cad.domain.Address" column="aid" unique="true"></many-to-one> ???????????</class> ????????</hibernate-mapping> ???????????Address.hbm.xml ?????????<hibernate-mapping > ???????????<class name="com.cad.domain.Address" table="address"> ???????????????<id name="id" column="id"> ???????????????????<generator class="native"></generator> ???????????????</id> ???????????????<property name="name" column="name"></property> ????????????????<!--property-ref属性指定通过从Company的address属性来查找自己--> ???????????????<one-to-one name="Company" class="com.cad.domain.Company" property-ref="address"></one-to-one> ???????????</class> ????????</hibernate-mapping> ?
测试：
????????????????public class Demo { ???????????????????private Session session; ???????????????????@Test ???????????????????public void test() { ???????????????????????//读取配置文件 ???????????????????????Configuration conf=new Configuration().configure(); ???????????????????????//根据配置创建factory ???????????????????????SessionFactory sessionfactory=conf.buildSessionFactory(); ???????????????????????session = sessionfactory.openSession(); ?????????????????????????Transaction ts=session.beginTransaction(); ???????????????????????Company c=new Company(); ???????????????????????c.setName("百度"); ???????????????????????Address a=new Address(); ???????????????????????a.setName("深圳"); ???????????????????????c.setAddress(a); ???????????????????????a.setCompany(c); ???????????????????????session.save(a); ???????????????????????session.save(c); ????????????????????????ts.commit(); ???????????????????????session.close(); ???????????????????????sessionfactory.close(); ???????????????????} ???????????????} ???????????默认情况下，一对一关联采用迫切左外连接检索策略。
三、按照主键映射
???实体类不变，我们编写一下配置文件 ???address的表的id字段既是主键又是外键. ???????编写配置文件 ???????Company.hbm.xml ?????????<hibernate-mapping > ???????????<class name="com.cad.domain.Company" table="company"> ???????????????<id name="id" column="id"> ???????????????????<generator class="native"></generator> ???????????????</id> ???????????????<property name="name" column="name"></property> ???????????????<one-to-one name="address" class="com.cad.domain.Address" ></one-to-one> ???????????</class> ????????</hibernate-mapping> ????????Address.hbm.xml ?????????<hibernate-mapping > ???????????<class name="com.cad.domain.Address" table="address"> ???????????????<id name="id" column="id"> ???????????????????<!--必须使用foreign标识符生成策略，还要指定哪个对象共享OID--> ???????????????????<generator class="foreign"> ???????????????????????<param name="property">company</param> ???????????????????</generator> ???????????????</id> ???????????????<property name="name" column="name"></property> ???????????????<!--constrained属性设为true，说明主键同时作为外键--> ???????????????<one-to-one name="company" class="com.cad.domain.Company" constrained="true"></one-to-one> ???????????</class> ????????</hibernate-mapping> ?
（十）Hibernate的一对一关联关系
原文地址：https://www.cnblogs.com/yuexiaoyun/p/9452411.html