Hibernate中映射一对一关联（按主键映射和外键映射）和组件映射

                                                    Hibernate中映射一对一关联（按主键映射和外键映射）和组件映射

Hibernate提供了两种映射一对一关联关系的方式：按照外键映射和按照主键映射。

下面以员工账号和员工档案表为例，介绍这两种映射方式，并使用这两种映射方式分别完成以下持久化操作：

(1)保存员工档案的同时分配给员工一个账号。

(2)加载员工档案的同时加载账号信息。

1.按照外键映射

步骤一：创建实体类Users1和Resume1

 package cn.happy.onetoone.fk;

 public class Resume1 {
     private Integer resId;
     private Integer resUserId;
     private String resName;
     private String resCardNo;
     private Users1 users1;

     public Integer getResId() {
         return resId;
     }
     public void setResId(Integer resId) {
         this.resId = resId;
     }
     public Integer getResUserId() {
         return resUserId;
     }
     public void setResUserId(Integer resUserId) {
         this.resUserId = resUserId;
     }
     public String getResName() {
         return resName;
     }
     public void setResName(String resName) {
         this.resName = resName;
     }
     public String getResCardNo() {
         return resCardNo;
     }
     public void setResCardNo(String resCardNo) {
         this.resCardNo = resCardNo;
     }
     public Users1 getUsers1() {
         return users1;
     }
     public void setUsers1(Users1 users1) {
         this.users1 = users1;
     }

 }

Resume1

 <?xml version="1.0"?>
 <!DOCTYPE hibernate-mapping PUBLIC
         "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
         "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
         <hibernate-mapping package="cn.happy.onetoone.fk">

         <class name="Resume1" table="Resume1">
         <id name="resId" column="RESID">
          <generator class="sequence">
          <param name="sequence">STU_SID</param>
          </generator>
         </id>
         <property name="resName" type="string" column="RESRNAME"></property>
         <property name="resCardNo" type="string" column="RESCARDNO"></property>
         <many-to-one name="users1" class="Users1" column="RESUSERSID" cascade="all" unique="true"></many-to-one>
         </class>

         </hibernate-mapping>

Resume1.hbm.xml

 package cn.happy.onetoone.fk;

 public class Users1 {
     private Integer userId;
     private String userName;
     private String userpass;
     public String getUserpass() {
         return userpass;
     }
     public void setUserpass(String userpass) {
         this.userpass = userpass;
     }
     private Resume1 resume1;

     public Integer getUserId() {
         return userId;
     }
     public void setUserId(Integer userId) {
         this.userId = userId;
     }
     public String getUserName() {
         return userName;
     }
     public void setUserName(String userName) {
         this.userName = userName;
     }

     public Resume1 getResume1() {
         return resume1;
     }
     public void setResume1(Resume1 resume1) {
         this.resume1 = resume1;
     }
 }

Users1.java

 <?xml version="1.0"?>
 <!DOCTYPE hibernate-mapping PUBLIC
         "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
         "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
         <hibernate-mapping package="cn.happy.onetoone.fk">

         <class name="Users1" table="Users1">
         <id name="userId" column="USERID">
          <generator class="sequence">
          <param name="sequence">STU_SID</param>
          </generator>
         </id>
         <property name="userName" type="string" column="USERNAME"></property>
         <property name="userpass" type="string" column="USERPASS"></property>
         <one-to-one name="resume1" class="Resume1" property-ref="users1"></one-to-one>
         </class>

         </hibernate-mapping>

Users1.hbm.xml

步骤二：配置文件Users1.hbm.xml和Resume1.hbm.xml

步骤三：测试方法书写

 package cn.happy.onetoone.fk;

 import org.hibernate.Session;
 import org.hibernate.Transaction;
 import org.junit.Test;

 import cn.happy.util.HibernateUtil;

 public class Testone {
     /**
      * 一对一    按外键映射
      * **/
      @Test
      public void onetoont(){
          Session session = HibernateUtil.currentSession();
          Transaction tx = session.beginTransaction();
          Resume1 re=new Resume1();
          re.setResName("学院不");
          re.setResCardNo("002");

          Users1 use=new Users1();
          use.setUserName("王喜");

          use.setResume1(re);
          re.setUsers1(use);

          session.save(re);
          tx.commit();
          HibernateUtil.closeSession();

      }

      @Test
      public void select(){
          Session session = HibernateUtil.currentSession();
          Transaction tx = session.beginTransaction();
          Users1 u =(Users1) session.get(Users1.class, 2);
          System.out.println(u.getResume1().getResName());
          tx.commit();
          HibernateUtil.closeSession();
      }

 }

测试

二：按照主键映射

步骤一：创建实体类Users2和Resume2

 package cn.happy.onetoone.pk;

 public class Resume2 {
     private Integer resId;
     private Integer resUserId;
     private String resName;
     private String resCardNo;
     private Users2 users1;

     public Integer getResId() {
         return resId;
     }
     public void setResId(Integer resId) {
         this.resId = resId;
     }
     public Integer getResUserId() {
         return resUserId;
     }
     public void setResUserId(Integer resUserId) {
         this.resUserId = resUserId;
     }
     public String getResName() {
         return resName;
     }
     public void setResName(String resName) {
         this.resName = resName;
     }
     public String getResCardNo() {
         return resCardNo;
     }
     public void setResCardNo(String resCardNo) {
         this.resCardNo = resCardNo;
     }
     public Users2 getUsers1() {
         return users1;
     }
     public void setUsers1(Users2 users1) {
         this.users1 = users1;
     }

 }

Resume2.java

 <?xml version="1.0"?>
 <!DOCTYPE hibernate-mapping PUBLIC
         "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
         "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
         <hibernate-mapping package="cn.happy.onetoone.pk">

         <class name="Resume2" table="Resume2">
         <id name="resId" column="RESID">
          <generator class="sequence">
          <param name="sequence">STU_SID</param>
          </generator>
         </id>
         <property name="resName" type="string" column="RESRNAME"></property>
         <property name="resCardNo" type="string" column="RESCARDNO"></property>
         <one-to-one name="users1" class="Users2" cascade="all" ></one-to-one>
         </class>

         </hibernate-mapping>

Resume2.hbm.xml

 package cn.happy.onetoone.pk;

 public class Users2 {
     private Integer userId;
     private String userName;
     private Resume2 resume1;

     public Integer getUserId() {
         return userId;
     }
     public void setUserId(Integer userId) {
         this.userId = userId;
     }
     public String getUserName() {
         return userName;
     }
     public void setUserName(String userName) {
         this.userName = userName;
     }

     public Resume2 getResume1() {
         return resume1;
     }
     public void setResume1(Resume2 resume1) {
         this.resume1 = resume1;
     }
 }

Users2.java

 <?xml version="1.0"?>
 <!DOCTYPE hibernate-mapping PUBLIC
         "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
         "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
         <hibernate-mapping package="cn.happy.onetoone.pk">

         <class name="Users2" table="Users2">
         <id name="userId" column="USERID">
          <generator class="foreign">
          <param name="property">resume1</param>
          </generator>
         </id>
         <property name="userName" type="string" column="USERNAME"></property>

         <one-to-one name="resume1" class="Resume2" constrained="true"></one-to-one>
         </class>

         </hibernate-mapping>

Users2.hbm.xml

步骤二：配置文件Users2.hbm.xml和Resume2.hbm.xml

步骤三：测试方法书写

 package cn.happy.onetoone.pk;

 import org.hibernate.Session;
 import org.hibernate.Transaction;
 import org.junit.Test;

 import cn.happy.util.HibernateUtil;

 public class Testone {
     /**
      * 一对一  按主键映射
      * */
      @Test
      public void onetoont(){
          Session session = HibernateUtil.currentSession();
          Transaction tx = session.beginTransaction();
          Resume2 re=new Resume2();
          re.setResName("学院不2");
          re.setResCardNo("2");

          Users2 use=new Users2();
          use.setUserName("王喜2");

          use.setResume1(re);
          re.setUsers1(use);

          session.save(re);
          tx.commit();
          HibernateUtil.closeSession();

      }

      @Test
      public void select(){
          Session session = HibernateUtil.currentSession();
          Transaction tx = session.beginTransaction();
          Users2 u =(Users2) session.get(Users2.class, 1);
          System.out.println(u.getResume1().getResName());
          tx.commit();
          HibernateUtil.closeSession();
      }

 }

测试代码

 3.组件映射

建立关系数据模型的一个重要原则是在不会导致数据冗余的前提下，尽可能减少数据库表的数目及表之间的外键参照关系。以员工信息为例，员工信息中有员工的家庭地址信息，如果把地址信息单独放在一张表中，然后建立员工信息表和地址信息表之间的外键参照关系，当每次查询员工信息时，都需建立者两个表的连接。建立表的连接是很耗时的操作，为了提高数据库运行性能，可以把这两张表的信息整合在一张员工信息表EMPINFO中

步骤一：创建EmpHomeAddress和EmpInfo

 package cn.happy.zujian;

 public class EmpInfo {
   private Integer eId;
   private String eName;
   private EmpHomeAddress eHome;

 public Integer geteId() {
     return eId;
 }
 public void seteId(Integer eId) {
     this.eId = eId;
 }
 public String geteName() {
     return eName;
 }
 public void seteName(String eName) {
     this.eName = eName;
 }
 public EmpHomeAddress geteHome() {
     return eHome;
 }
 public void seteHome(EmpHomeAddress eHome) {
     this.eHome = eHome;
 }
 }

EmpInfo.java

 package cn.happy.zujian;

 public class EmpHomeAddress {
   private String ehomestreet;
   private String ehomecity;
   private String ehomeprovince;
   private String ehomezipcode;

   private EmpInfo empinfo;
 public EmpInfo getEmpinfo() {
     return empinfo;
 }
 public void setEmpinfo(EmpInfo empinfo) {
     this.empinfo = empinfo;
 }
 public String getEhomestreet() {
     return ehomestreet;
 }
 public void setEhomestreet(String ehomestreet) {
     this.ehomestreet = ehomestreet;
 }
 public String getEhomecity() {
     return ehomecity;
 }
 public void setEhomecity(String ehomecity) {
     this.ehomecity = ehomecity;
 }
 public String getEhomeprovince() {
     return ehomeprovince;
 }
 public void setEhomeprovince(String ehomeprovince) {
     this.ehomeprovince = ehomeprovince;
 }
 public String getEhomezipcode() {
     return ehomezipcode;
 }
 public void setEhomezipcode(String ehomezipcode) {
     this.ehomezipcode = ehomezipcode;
 }

 }

EmpHomeAddress

 <?xml version="1.0"?>
 <!DOCTYPE hibernate-mapping PUBLIC
         "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
         "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
         <hibernate-mapping package="cn.happy.zujian">

         <class name="EmpInfo" table="EMPINFO">
         <id name="eId" column="EID">
          <generator class="sequence">
          <param name="sequence">STU_SID</param>
          </generator>
         </id>
         <property name="eName" type="string" column="ENAME"></property>

         <component name="eHome" class="EmpHomeAddress">
         <parent name="empinfo"/>
         <property name="ehomestreet" column="EHOMESTREET" type="string"></property>
         <property name="ehomecity" column="EHOMECITY" type="string"></property>
         <property name="ehomeprovince" column="EHOMEPROVINCE" type="string"></property>
         <property name="ehomezipcode" column="EHOMEZIPCODE" type="string"></property>
         </component>

         </class>

         </hibernate-mapping>

EmpInfo.hbm.xml

步骤二：创建配置文件EmpInfo.hbm.xml

步骤三：书写测试类

 package cn.happy.zujian;

 import org.hibernate.Session;
 import org.hibernate.Transaction;
 import org.junit.Test;

 import cn.happy.util.HibernateUtil;

 public class TestInfo {
     /**
      * 组件映射
      * */
   @Test
   public void zujian(){
       Session session = HibernateUtil.currentSession();
       Transaction tx = session.beginTransaction();

       EmpInfo empinfo=new EmpInfo();
       empinfo.seteName("回青");

       EmpHomeAddress address=new EmpHomeAddress();
       address.setEhomecity("北京");
       address.setEhomeprovince("北京市");
       address.setEhomestreet("成府路");
       address.setEhomezipcode("10002");
       empinfo.seteHome(address);

       session.save(empinfo);
       tx.commit();

       HibernateUtil.closeSession();

   }
 }

测试代码