Hibernate提供了两种一对一映射关联关系的方式：
1）按照外键映射
2）按照主键映射
下面以员工账号表和员工档案表（员工账号和档案表之间是一对一的关系）为例，介绍这两种映射关系,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
一:按照外键映射
HibernateUtil工具类（用于获取session和关闭session）
package cn.util;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
//初始化一个ThreadLocal对象，有get和set方法
private static final ThreadLocal<Session> sessionTL=new ThreadLocal<Session>();
private static Configuration configuration;
private final static SessionFactory sessionFactory;
static{
configuration=new Configuration().configure();
sessionFactory=configuration.buildSessionFactory();
}
//获得session对象
public static Session currentSession() {
//sessionTL的get方法根据当前线程返回其对应的线程内部变量，即Session对象，多线程情况下共享数据库连接是不安全的。
//ThreadLocal保证了每个线程都有自己的session对象
Session session=(Session)sessionTL.get();
if (session==null) {
session=sessionFactory.openSession();
sessionTL.set(session);
}
return session;
}
//关闭session对象
public static void closeSession() {
Session session=(Session)sessionTL.get();
sessionTL.set(null);
session.close();
}
}
创建实体类Users1和Resume1
Users1：
package cn.entity_fk;
/**
* 员工类
*
*
*
*/
public class Users1 {
private Integer userid;//用户编号
private String username;//名称
private String userpass;//密码
private Resume1 resume1;//档案对象
public Users1() {
}
public Users1(String username, String userpass) {
this.username = username;
this.userpass = userpass;
}
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 String getUserpass() {
return userpass;
}
public void setUserpass(String userpass) {
this.userpass = userpass;
}
public Resume1 getResume1() {
return resume1;
}
public void setResume1(Resume1 resume1) {
this.resume1 = resume1;
}
}
Resume1:
package cn.entity_fk;
/**
* 档案类
*
* @time
* @author Happy
*
*/
public class Resume1 {
private Integer resid; //档案编号
private String resname; //档案名称
private String rescardno;//编号
private Users1 users1; //隶属的用户（员工）
public Resume1() {
}
public Resume1( String resname, String rescardno) {
this.resname = resname;
this.rescardno = rescardno;
}
public Integer getResid() {
return resid;
}
public void setResid(Integer resid) {
this.resid = resid;
}
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;
}
}
创建配置文件Users1.hbm.xml和Resume1.hbm.xml
Users1.hbm.xml:
<?xml version="1.0" encoding="UTF-8"?>
<!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.entity_fk">
<class name="Users1" table="USERS1">
<!-- 主键的配置 -->
<id name="userid" column="USERID" >
<!-- 由后台数据库生成主键：默认生成的序列名称为：Hibernate_Sequence -->
<generator class="native"></generator>
</id>
<property name="username" column="USERNAME" type="string"></property>
<property name="userpass" column="USERPASS" type="string"></property>
<!-- 配置一对对，外键方式的关联
property-ref:通过Resume1 的users1的属性，建立了从users1到Resume1的对象的关联！
-->
<one-to-one name="resume1" class="Resume1" property-ref="users1"></one-to-one>
</class>
</hibernate-mapping>
Resume1.hbm.xml:
<?xml version="1.0" encoding="UTF-8"?>
<!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.entity_fk">
<class name="Resume1" table="RESUME1">
<id name="resid" column="RESID" >
<generator class="native"></generator>
</id>
<property name="resname" column="RESNAME" type="string"></property>
<property name="rescardno" column="RESCARDNO" type="string"></property>
<many-to-one name="users1" class="Users1" cascade="all" column="RESUSERID" unique="true"></many-to-one>
</class>
</hibernate-mapping>
hibernate.cfg.xml大配置文件:
<?xml version=‘1.0‘ encoding=‘utf-8‘?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- Database connection settings -->
<property name="connection.driver_class">oracle.jdbc.OracleDriver</property>
<property name="connection.url">jdbc:oracle:thin:@localhost:1521:orcl</property>
<property name="connection.username">***</property>
<property name="connection.password">***</property>
<!-- SQL dialect (SQL 方言)-->
<property name="dialect">org.hibernate.dialect.Oracle10gDialect</property>
<!-- Drop and re-create the database schema on startup -->
<property name="hbm2ddl.auto">create</property>
<!-- Echo all executed SQL to stdout 在控制台打印后台的SQL语句-->
<property name="show_sql">true</property>
<!-- 格式化显示SQL -->
<property name="format_sql">true</property>
<!-- JDBC connection pool (use the built-in) -->
<!-- <property name="connection.pool_size">1</property> -->
<!-- Enable Hibernate‘s automatic session context management 指定当前session范围和上下文-->
<!-- <property name="current_session_context_class">thread</property> -->
<!-- Disable the second-level cache -->
<!-- <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>-->
<mapping resource="cn/zhang/entity/Resume1.hbm.xml" />
<mapping resource="cn/zhang/entity/Users1.hbm.xml" />
</session-factory>
</hibernate-configuration>
测试类：
/**
* 一对一关联测试
*/
public class Tests {
Session session;
Transaction tx;
@Before
public void initDate(){
session = HibernateUtil.getSession();
tx= session.beginTransaction();
}
@After
public void afterTest(){
tx.commit();
HibernateUtil.closeSession();
}
/**
* 一对一关联测试
*/
@Test
public void getTest(){
Users1 u1=new Users1();
u1.setUsername("火");
u1.setUserpass("2");
Resume1 r1=new Resume1();
r1.setResname("培训2");
r1.setRescardno("002");
u1.setResume1(r1);
r1.setUsers1(u1);
session.save(r1);
System.out.println("ok-------");
}
/**
* 查询
*/
@Test
public void selectTest(){
Users1 u1=(Users1)session.load(Users1.class, 2);
System.out.println(u1.getResume1().getResname());
}
结果：
数据库：
数据库：
Users1表:
Resume1表：
二：按照主键映射
Users2表的userid字段是主键，同时作为外键参照Resume2表的主键，即Users2表与Resume2表共享主键（Users2中的主键值是根据Resume2生成的主键值取值的）
Resume2:
package cn.entity_pk;
/**
* 档案类
*
* @time
* @author Happy
*
*/
public class Resume2 {
private Integer resid;
private String resname;
private String rescardno;
private Users2 users2;
public Users2 getUsers2() {
return users2;
}
public void setUsers2(Users2 users2) {
this.users2 = users2;
}
public Resume2() {
}
public Resume2( String resname, String rescardno) {
this.resname = resname;
this.rescardno = rescardno;
}
public Integer getResid() {
return resid;
}
public void setResid(Integer resid) {
this.resid = resid;
}
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;
}
}
Users2：
package cn.entity_pk;
/**
* 员工类
*
* @author Happy
*
*/
public class Users2 {
private Integer userid;
private String username;
private String userpass;
private Resume2 resume2;
public Resume2 getResume2() {
return resume2;
}
public void setResume2(Resume2 resume2) {
this.resume2 = resume2;
}
public Users2() {
}
public Users2(String username, String userpass) {
this.username = username;
this.userpass = userpass;
}
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 String getUserpass() {
return userpass;
}
public void setUserpass(String userpass) {
this.userpass = userpass;
}
}
Resume2.hbm.xml映射文件：
<?xml version="1.0" encoding="UTF-8"?>
<!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.entity_pk">
<class name="Resume2" table="RESUME2">
<id column="RESID" name="resid">
<generator class="sequence">
<param name="sequence">SEQ_NUM</param>
</generator>
</id>
<property column="RESNAME" name="resname" type="string"/>
<property column="RESCARDNO" name="rescardno" type="string"/>
<!--主的一方 -->
<one-to-one name="users2" cascade="all" class="Users2" />
</class>
</hibernate-mapping>
Users2.hbm.xml映射文件:
<?xml version="1.0" encoding="UTF-8"?>
<!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.entity_pk">
<class name="Users2" table="USERS2">
<id name="userid" column="USERID" >
<generator class="foreign">
<param name="property">resume2</param>
</generator>
</id>
<property name="username" column="USERNAME" type="string"></property>
<property name="userpass" column="USERPASS" type="string"></property>
<!-- constrained:用来约束 在底层USERS2数据表中，植入外键-->
<one-to-one name="resume2" class="Resume2" constrained="true"></one-to-one>
</class>
</hibernate-mapping>
测试类：
public class Test_pk {
Session session;
Transaction tx;
@Before
public void initDate(){
session = HibernateUtil.getSession();
tx= session.beginTransaction();
}
@After
public void afterTest(){
tx.commit();
HibernateUtil.closeSession();
}
/**
* 一对一关联测试:按照主键映射
*/
@Test
public void getTest(){
Users2 u1=new Users2();
u1.setUsername("呵呵");
u1.setUserpass("1");
Resume2 r1=new Resume2();
r1.setResname("哈哈");
r1.setRescardno("001");
u1.setResume2(r1);
r1.setUsers2(u1);
session.save(r1);
System.out.println("ok-------");
}
/**
* 查询
*/
@Test
public void selectTest(){
Users2 u1=(Users2)session.load(Users2.class, 2);
System.out.println(u1.getResume2().getResname());
}
结果：
数据库：
Resume2表：
Users2表：
时间： 2024-11-07 12:19:37