一对一关联

Hibernate中的一对一关联

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

一丶按照外键映射

Users1中：

 1 package cn.xsy.entity.day_onetoone;
 2 
 3 /**
 4  * Created by Administrator on 2017/12/30.
 5  */
 6 public class Users1 {
 7 
 8     private Integer userid;
 9 
10     private String username;
11 
12     private String userpass;
13 
14     private Resume1 resume1;
15 
16     public Integer getUserid() {
17         return userid;
18     }
19 
20     public void setUserid(Integer userid) {
21         this.userid = userid;
22     }
23 
24     public String getUsername() {
25         return username;
26     }
27 
28     public void setUsername(String username) {
29         this.username = username;
30     }
31 
32     public String getUserpass() {
33         return userpass;
34     }
35 
36     public void setUserpass(String userpass) {
37         this.userpass = userpass;
38     }
39 
40     public Resume1 getResume1() {
41         return resume1;
42     }
43 
44     public void setResume1(Resume1 resume1) {
45         this.resume1 = resume1;
46     }
47 }

Users1.hbm.xml中:

 1 <?xml version="1.0"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC
 3         "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 4         "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
 5 <!--根节点-->
 6 <!-- package:要映射的对象所在的包（可选，如果不指定，此文件下所有的类都要指定全路径）
 7     auto-import 默认为true，在写HQL的时候自动导入包名
 8             如果指定为false，在写HQL的时候必须要写上类的全名-->
 9 <hibernate-mapping package="cn.xsy.entity.day_onetoone">
10     <class name="Users1" table="USERS1">
11         <id name="userid" column="USERID" >
12             <generator class="native"></generator>
13         </id>
14         <property name="username" column="USERNAME" type="string"></property>
15         <property name="userpass" column="USERPASS" type="string"></property>
16         <one-to-one name="resume1" class="Resume1" property-ref="users1"></one-to-one>
17     </class>
18 </hibernate-mapping>

Resume1中：

 1 package cn.xsy.entity.day_onetoone;
 2 
 3 /**
 4  * Created by Administrator on 2017/12/30.
 5  */
 6 public class Resume1 {
 7 
 8     private Integer resid;
 9 
10     private String resname;
11 
12     private String rescardno;
13 
14     private Users1 users1;
15 
16     public Integer getResid() {
17         return resid;
18     }
19 
20     public void setResid(Integer resid) {
21         this.resid = resid;
22     }
23 
24     public String getResname() {
25         return resname;
26     }
27 
28     public void setResname(String resname) {
29         this.resname = resname;
30     }
31 
32     public String getRescardno() {
33         return rescardno;
34     }
35 
36     public void setRescardno(String rescardno) {
37         this.rescardno = rescardno;
38     }
39 
40     public Users1 getUsers1() {
41         return users1;
42     }
43 
44     public void setUsers1(Users1 users1) {
45         this.users1 = users1;
46     }
47 }

Resume1.hbm.xml中：

 1 <?xml version="1.0"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC
 3         "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 4         "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
 5 <!--根节点-->
 6 <!-- package:要映射的对象所在的包（可选，如果不指定，此文件下所有的类都要指定全路径）
 7     auto-import 默认为true，在写HQL的时候自动导入包名
 8             如果指定为false，在写HQL的时候必须要写上类的全名-->
 9 <hibernate-mapping package="cn.xsy.entity.day_onetoone">
10     <class name="Resume1" table="RESUME1">
11         <id name="resid" column="RESID" >
12             <generator class="native"></generator>
13         </id>
14         <property name="resname" column="RESNAME" type="string"></property>
15         <property name="rescardno" column="RESCARDNO" type="string"></property>
16         <many-to-one name="users1" class="Users1" cascade="all" column="RESUSERID" unique="true"></many-to-one>
17     </class>
18 </hibernate-mapping>

hibernate.cfgonetoone.xml中：

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE hibernate-configuration PUBLIC
 3         "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
 4         "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
 5 
 6 <hibernate-configuration>
 7    <!--创建Session的基础配置-->
 8     <session-factory>
 9         <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
10         <property name="connection.url">jdbc:oracle:thin:@localhost:1521:orcl</property>
11         <property name="connection.username">waxsy</property>
12         <property name="connection.password">bsfm</property>
13 
14         <!-- JDBC 连接池(use the built-in) -->
15    <!--     <property name="connection.pool_size">1</property>-->
16 
17         <!-- SQL dialect （方言）-->
18         <property name="dialect">org.hibernate.dialect.Oracle10gDialect</property>
19 
20         <!-- Enable Hibernate's automatic session context management
21           session工厂创建的session和当前线程绑定bind
22          -->
23         <property name="current_session_context_class">thread</property>
24 
25         <!-- Disable the second-level cache  启用/关闭二级缓存-->
26        <!-- <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>-->
27 
28         <!-- Echo   all executed SQL to stdout 在控制台打印sql -->
29         <property name="show_sql">true</property>
30         <!--格式化SQL-->
31         <property name="format_sql">true</property>
32         <!-- Drop and re-create （重新创建）the database schema（架构） on startup （启动）
33          是否根据hbm.xml自动建表 建表的策略 update create
34          hbm配置文件》》》》》》》ddl  数据表
35          create: 过程：先drop 再Create
36          update:检查现有表的架构是否存在，真实开发中，在上线后，一定update
37         -->
38         <property name="hbm2ddl.auto">update</property>
39          <!--关联小配置 -->
40 
41 
42         <mapping resource="cn/xsy/entity/day_onetoone/Users1.hbm.xml"/>
43         <mapping resource="cn/xsy/entity/day_onetoone/Resume.hbm.xml"/>
44     </session-factory>
45 
46 </hibernate-configuration
47 >

Test20171230_onetoone中：

 1 package day01;
 2 
 3 
 4 import cn.xsy.entity.day_manytomanydouble.Employee;
 5 import cn.xsy.entity.day_manytomanydouble.Project;
 6 import cn.xsy.entity.day_onetomanydouble.Dept;
 7 import cn.xsy.entity.day_onetomanydouble.Emp;
 8 import cn.xsy.entity.day_onetoone.Resume1;
 9 import cn.xsy.entity.day_onetoone.Users1;
10 import cn.xsy.util.HibernateUtil;
11 import org.hibernate.Query;
12 import org.hibernate.Session;
13 import org.hibernate.Transaction;
14 import org.junit.Test;
15 
16 import java.util.List;
17 import java.util.Set;
18 
19 /**
20  * Created by Happy on 2017-12-24.
21  */
22 public class Test20171230_onetoone {
23 
24     //一对一关联
25    @Test
26    public void onetoone(){
27 
28        Session session = HibernateUtil.getSession();
29        Transaction tx=session.beginTransaction();
30        //创建一个用户对象
31        Users1 u1=new Users1();
32        u1.setUserid(1);
33        u1.setUsername("小涩瑶");
34        //创建一个档案对象
35        Resume1 r1=new Resume1();
36        r1.setResid(1);
37        r1.setResname("余浪北笙");
38        u1.setResume1(r1);
39        r1.setUsers1(u1);
40        //保存r1自动保存u1
41        session.save(r1);
42        tx.commit();
43        System.out.println("add ok!");
44 
45    }
46 
47     
48 }

二丶按照主键映射