• 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 
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        6     
       
         7         
        
         root
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         123456
         9         
        
         com.mysql.jdbc.Driver
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         jdbc:mysql://localhost/hibernate_01
        11 12         
        14         
        
         org.hibernate.dialect.MySQL5InnoDBDialect
        15 16         
        
         true
        17 18         
        
         true
        19 20         
        
         update
        21 22         
        
         thread
        23 24         
        
         500
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         20
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         10
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         2000
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         2000
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         10
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       36 
      

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

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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

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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=InnoDB16 Hibernate: 17     18     alter table DEPARMENTS 19        drop index UK_j9bdvgylyeboig73ntlfcuyf620 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     into11         DEPARMENTS12         (DEPART_NAME, MANAGER_ID) 13     values14         (?, ?)

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deparment13         // 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manager18         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     }