Hibernate（八）：基于外键映射的1-1关联关系

• 背景：

一个部门只有一个一把手，这在程序开发中就会设计数据映射应该设置为一对一关联。

在hibernate代码开发中，实现这个业务有两种方案：

1）基于外键映射的1-1关联；

2）基于主键映射的1-1关联。

本篇文章主要是用来学习如何使用外键实现1-1关联关系。

• 新建项目hibernate05

新建java project,引入依赖包，在src下添加hibernate.cfg.xml

 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 <hibernate-configuration>
 6     <session-factory>
 7         <property name="hibernate.connection.username">root</property>
 8         <property name="hibernate.connection.password">123456</property>
 9         <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
10         <property name="hibernate.connection.url">jdbc:mysql://localhost/hibernate_01</property>
11
12         <!-- <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
13             <property name="hibernate.dialect">org.hibernate.dialect.MySQLInnoDBDialect</property> -->
14         <property name="hibernate.dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>
15
16         <property name="hibernate.show_sql">true</property>
17
18         <property name="hibernate.format_sql">true</property>
19
20         <property name="hibernate.hbm2ddl.auto">update</property>
21
22         <property name="hibernate.current_session_context_class">thread</property>
23
24         <property name="hibernate.c3p0.max_size">500</property>
25         <property name="hibernate.c3p0.min_size">20</property>
26         <property name="hibernate.c3p0.max_statements">10</property>
27         <property name="hibernate.c3p0.timeout">2000</property>
28         <property name="hibernate.c3p0.idle_test_period">2000</property>
29         <property name="hibernate.c3p0.acquire_increment">10</property>
30
31         <mapping resource="com/dx/hibernate005/onetoonebyforigenkey/Deparment.hbm.xml" />
32         <mapping class="com.dx.hibernate005.onetoonebyforigenkey.Deparment" />
33         <mapping resource="com/dx/hibernate005/onetoonebyforigenkey/Manager.hbm.xml" />
34         <mapping class="com.dx.hibernate005.onetoonebyforigenkey.Manager" />
35     </session-factory>
36 </hibernate-configuration>

在src下新建包com.dx.hibernate005.onetoonebyforigenkey

在com.dx.hibernate005.onetoonebyforigenkey包下创建

Deparment.java

 1 package com.dx.hibernate005.onetoonebyforigenkey;
 2
 3 public class Deparment {
 4     private Integer departId;
 5     private String departName;
 6     private Manager manager;
 7
 8     public Deparment() {
 9         super();
10     }
11
12     public Deparment(Integer departId, String departName) {
13         super();
14         this.departId = departId;
15         this.departName = departName;
16     }
17
18     public Integer getDepartId() {
19         return departId;
20     }
21
22     public void setDepartId(Integer departId) {
23         this.departId = departId;
24     }
25
26     public String getDepartName() {
27         return departName;
28     }
29
30     public void setDepartName(String departName) {
31         this.departName = departName;
32     }
33
34     public Manager getManager() {
35         return manager;
36     }
37
38     public void setManager(Manager manager) {
39         this.manager = manager;
40     }
41
42 }

Deparment.hbm.xml

 1 <?xml version="1.0"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 3 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
 4 <!-- Generated 2017-6-2 10:54:26 by Hibernate Tools 3.5.0.Final -->
 5 <hibernate-mapping>
 6     <class name="com.dx.hibernate005.onetoonebyforigenkey.Deparment" table="DEPARMENTS">
 7         <id name="departId" type="java.lang.Integer">
 8             <column name="DEPART_ID" />
 9             <generator class="native" />
10         </id>
11         <property name="departName" type="java.lang.String">
12             <column name="DEPART_NAME" />
13         </property>
14
15         <!-- 在Deparment中定义一个Many-to-one就可以实现在Deparments表中多一个外键列 -->
16         <many-to-one name="manager" class="com.dx.hibernate005.onetoonebyforigenkey.Manager" column="MANAGER_ID" unique="true"></many-to-one>
17     </class>
18 </hibernate-mapping>

Manager.java

 1 package com.dx.hibernate005.onetoonebyforigenkey;
 2
 3 public class Manager {
 4     private Integer managerId;
 5     private String managerName;
 6     private Deparment deparment;
 7
 8     public Manager() {
 9         super();
10     }
11
12     public Manager(Integer managerId, String managerName) {
13         super();
14         this.managerId = managerId;
15         this.managerName = managerName;
16     }
17
18     public Integer getManagerId() {
19         return managerId;
20     }
21
22     public void setManagerId(Integer managerId) {
23         this.managerId = managerId;
24     }
25
26     public String getManagerName() {
27         return managerName;
28     }
29
30     public void setManagerName(String managerName) {
31         this.managerName = managerName;
32     }
33
34     public Deparment getDeparment() {
35         return deparment;
36     }
37
38     public void setDeparment(Deparment deparment) {
39         this.deparment = deparment;
40     }
41
42 }

Deparment.hbm.xml

 1 <?xml version="1.0"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 3 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
 4 <!-- Generated 2017-6-2 10:54:26 by Hibernate Tools 3.5.0.Final -->
 5 <hibernate-mapping>
 6     <class name="com.dx.hibernate005.onetoonebyforigenkey.Manager" table="MANAGERS">
 7         <id name="managerId" type="java.lang.Integer">
 8             <column name="MANAGER_ID" />
 9             <generator class="native" />
10         </id>
11         <property name="managerName" type="java.lang.String">
12             <column name="MANAGER_NAME" />
13         </property>
14
15         <!-- 在对应的数据表中已经有了外键，当前持久化类使用one-to-one进行映射 -->
16         <one-to-one name="deparment" class="com.dx.hibernate005.onetoonebyforigenkey.Deparment" property-ref="manager"></one-to-one>
17     </class>
18 </hibernate-mapping>

TestMain.java测试类,并引入JUnit4所需的依赖包。

package com.dx.hibernate005.onetoonebyforigenkey;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.boot.Metadata;
import org.hibernate.boot.MetadataSources;
import org.hibernate.boot.model.naming.ImplicitNamingStrategyComponentPathImpl;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

public class TestMain {
    private SessionFactory sessionFactory = null;
    private Session session = null;
    private Transaction transaction = null;

    @Before
    public void init() {
        StandardServiceRegistry standardRegistry = new StandardServiceRegistryBuilder().configure().build();
        Metadata metadata = new MetadataSources(standardRegistry).getMetadataBuilder().applyImplicitNamingStrategy(ImplicitNamingStrategyComponentPathImpl.INSTANCE).build();

        sessionFactory = metadata.getSessionFactoryBuilder().build();
        session = sessionFactory.getCurrentSession();
        transaction = session.beginTransaction();
    }

    @After
    public void destory() {
        transaction.commit();
        session.close();
        sessionFactory.close();
    }
}

运行空测试类，初始化sql:

 1 Hibernate:
 2
 3     create table DEPARMENTS (
 4        DEPART_ID integer not null auto_increment,
 5         DEPART_NAME varchar(255),
 6         MANAGER_ID integer,
 7         primary key (DEPART_ID)
 8     ) engine=InnoDB
 9 Hibernate:
10
11     create table MANAGERS (
12        MANAGER_ID integer not null auto_increment,
13         MANAGER_NAME varchar(255),
14         primary key (MANAGER_ID)
15     ) engine=InnoDB
16 Hibernate:
17
18     alter table DEPARMENTS
19        drop index UK_j9bdvgylyeboig73ntlfcuyf6
20 Hibernate:
21
22     alter table DEPARMENTS
23        add constraint UK_j9bdvgylyeboig73ntlfcuyf6 unique (MANAGER_ID)
24 Hibernate:
25
26     alter table DEPARMENTS
27        add constraint FKnlmf88ii3maigw7hgc182cqi4
28        foreign key (MANAGER_ID)
29        references MANAGERS (MANAGER_ID)

• 测试：

1)测试insert:

 1     @Test
 2     public void testInsert(){
 3         Deparment deparment=new Deparment();
 4         deparment.setDepartName("Depart1");
 5
 6         Manager manager=new Manager();
 7         manager.setManagerName("manager1");
 8
 9         deparment.setManager(manager);
10         manager.setDeparment(deparment);
11
12         session.save(manager);
13         session.save(deparment);
14     }
15     

测试通过，测试打印sql

 1 Hibernate:
 2     insert
 3     into
 4         MANAGERS
 5         (MANAGER_NAME)
 6     values
 7         (?)
 8 Hibernate:
 9     insert
10     into
11         DEPARMENTS
12         (DEPART_NAME, MANAGER_ID)
13     values
14         (?, ?)

2)测试select

 1     @Test
 2     public void testSelect() {
 3         // 1.查询时，采用懒加载。
 4         Deparment deparment = (Deparment) session.get(Deparment.class, 1);
 5         System.out.println(deparment.getDepartName());
 6
 7         // // 2.会出现懒加载异常问题
 8         // session.close();
 9         // Manager manager = deparment.getManager();
10         // System.out.println(manager.getClass());
11         // System.out.println(manager.getManagerName());
12     }

3)测试Select Manager

 1     @Test
 2     public void testSelectManager() {
 3         // 1.查询时，没采用懒加载。
 4         Manager manager = session.get(Manager.class, 1);
 5         System.out.println(manager.getManagerName());
 6
 7         // 2.不会出现懒加载异常问题
 8         session.close();
 9         System.out.println(manager.getDeparment().getDepartName());
10     }

4)测试修改

 1     @Test
 2     public void testUpdate() {
 3         // // 1) session关闭时，修改执行
 4         // Manager manager = session.get(Manager.class, 1);
 5         // manager.setManagerName("Mgr11111");
 6         // // session.save(manager);
 7         //
 8         // Deparment deparment = session.get(Deparment.class, 1);
 9         // deparment.setDepartName("Depart111111");
10         // // session.save(deparment);
11
12         // // 2)通过manager 关联修改deparment
13         // Manager manager = session.get(Manager.class, 1);
14         // manager.setManagerName("Mgr222");
15         // manager.getDeparment().setDepartName("DEPT22");
16
17         // 3)通过department关联修改manager
18         Deparment deparment = session.get(Deparment.class, 1);
19         deparment.setDepartName("DPT333");
20         deparment.getManager().setManagerName("Mgr333");
21     }

5）测试删除

 1     @Test
 2     public void testDelete() {
 3         // 1）在department表中有记录与之关联时，删除失败
 4         // Manager manager = session.get(Manager.class, 1);
 5         // session.delete(manager);
 6
 7         // 2)删除成功，只删除了deparment表中的记录，manger表中的记录并没有删除，之后再删除manager就不会出现错误。
 8         Deparment deparment = session.get(Deparment.class, 1);
 9         session.delete(deparment);
10     }