hibernate中一對一的關聯有兩種方式：一種是採用外來鍵關聯，另外一種是採用主鍵關聯。

 最近專案中用到一對一主鍵雙向關聯，並且是基於註解的方式。期間遇到一些問題，現在貼出來探討探討。

 一個丈夫(husband)對應一個妻子(wife)，主要目標是在儲存丈夫或者妻子時，關聯的物件也被儲存。具體程式碼如下：

 husband類： 

package cn.edu.dlnu.resources.model.entity;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.PrimaryKeyJoinColumn;

@Entity
public class Husband {
 private int id;
 private String name;
 private Wife wife;
 @Id
 @GeneratedValue//主鍵生成器
 public int getId(){
  return id;
 }
 public String getName() {
  return name;
 }
@OneToOne(cascade=CascadeType.ALL)
 @PrimaryKeyJoinColumn//這個註解只能寫在主(生成ID)的一端
 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;
 }
}
 wife類：

package cn.edu.dlnu.resources.model.entity;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import org.hibernate.annotations.GenericGenerator;
import org.hibernate.annotations.Parameter;

@Entity
public class Wife {
 private int id;
 private String name;
 private Husband husband;
 
 @Id
 @GenericGenerator(name="pkGenerator",strategy="foreign",parameters={@Parameter(name="property",value="husband")})
   @GeneratedValue(generator="pkGenerator")

//wife的ID是根據husband的ID來賦值的，這裡需要設定ID生成器的策略為foreign，引數中指定wife的ID是使用husband物件中的ID
 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 void setHusband(Husband husband) {
  this.husband = husband;
 }
 @OneToOne(cascade=CascadeType.ALL,mappedBy="wife")

 public Husband getHusband() {
  return husband;
 }
}
 OneToOnePKTest類：

package cn.edu.dlnu.resources.model.entity;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.tool.hbm2ddl.SchemaExport;
import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.Test;

import cn.edu.dlnu.resources.model.entity.Husband;
import cn.edu.dlnu.resources.model.entity.Wife;

public class OneToOnePKTest {
 private static SessionFactorysessionFactory;
 
 @BeforeClass
 public static void beforeClass() {
   sessionFactory= newAnnotationConfiguration().configure().buildSessionFactory();
 }
 @AfterClass
 public static void afterClass() {
  sessionFactory.close();
 }
 
 @Test
 public void testSave(){
  Session s =sessionFactory.getCurrentSession();
  s.beginTransaction();
  
  Husband h = newHusband();
  Wife w = new Wife();
  w.setName("w");
  h.setName("h");

  h.setWife(w);
  w.setHusband(h);
  s.save(w);
  s.getTransaction().commit();
 }

@Test
 public void testSchemaExport() {
  new SchemaExport(newAnnotationConfiguration().configure()).create(false, true);
 }
 public static void main(String[] args) {
  beforeClass();
  newOneToOnePKTest().testSave();
  afterClass();
 }
}

hibernate生成的資料庫表：create table Husband (
       id integer not null auto_increment,
       name varchar(255),
       primary key (id)
    )；

create table Wife (
       id integer not null,
       name varchar(255),
       primary key (id)
    )
執行testSave()，方法後資料庫中husband 與 wife表中記錄的主鍵一致。