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1.映射一对一关联关系
1）域模型
2）关系数据模型:
2.基于外键映射的 1-1
1)对于基于外键的1-1关联，其外键可以存放在任意一边，在需要存放外键一端，增加many-to-one元素。为many-to-one元素增加unique=“true” 属性来表示为1-1关联
1 <!-- 使用 many-to-one 的方式来映射 1-1 关联关系 --> 2 <many-to-one name="mgr" class="Manager"> 3 <column name="MGR_ID" unique="true"></column> 4 </many-to-one>
2)另一端需要使用one-to-one元素，该元素使用 property-ref 属性指定使用被关联实体主键以外的字段作为关联字段
1 <!-- 映射 1-1 的关联关系：在对应的数据表中已经有外键了，当前持久化类使用 one-to-one 进行映射 2 需要使用one-to-one元素，该元素使用 property-ref 属性指定使用被关联实体主键以外的字段作为关联字段 3 --> 4 <one-to-one name="dept" class="Department" property-ref="mgr"></one-to-one>
Manager
1 package com.jason.hibernate.entities.foreign.one2one;
2
3 public class Manager {
4
5 private Integer mgrId;
6 private String mgrName;
7 private Department dept;
8
9 public Integer getMgrId() {
10 return mgrId;
11 }
12
13 public void setMgrId(Integer mgrId) {
14 this.mgrId = mgrId;
15 }
16
17 public String getMgrName() {
18 return mgrName;
19 }
20
21 public void setMgrName(String mgrName) {
22 this.mgrName = mgrName;
23 }
24
25 public Department getDept() {
26 return dept;
27 }
28
29 public void setDept(Department dept) {
30 this.dept = dept;
31 }
32
33 }
Department
1 package com.jason.hibernate.entities.foreign.one2one;
2
3 public class Department {
4 private Integer deptId;
5 private String deptName;
6
7 private Manager mgr;
8
9 public Integer getDeptId() {
10 return deptId;
11 }
12
13 public void setDeptId(Integer deptId) {
14 this.deptId = deptId;
15 }
16
17 public String getDeptName() {
18 return deptName;
19 }
20
21 public void setDeptName(String deptName) {
22 this.deptName = deptName;
23 }
24
25 public Manager getMgr() {
26 return mgr;
27 }
28
29 public void setMgr(Manager mgr) {
30 this.mgr = mgr;
31 }
32
33 }
Department.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 2016-10-5 22:31:35 by Hibernate Tools 3.4.0.CR1 --> 5 <hibernate-mapping package="com.jason.hibernate.entities.foreign.one2one"> 6 <class name="Department" table="DEPARTMENT"> 7 8 <id name="deptId" type="java.lang.Integer"> 9 <column name="DEPT_ID" /> 10 <generator class="native" /> 11 </id> 12 13 <property name="deptName" type="java.lang.String"> 14 <column name="DEPT_NAME" /> 15 </property> 16 17 <!-- 使用 many-to-one 的方式来映射 1-1 关联关系 --> 18 <many-to-one name="mgr" class="Manager"> 19 <column name="MGR_ID" unique="true"></column> 20 </many-to-one> 21 22 </class> 23 24 </hibernate-mapping>
Manager.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 2016-10-5 22:31:35 by Hibernate Tools 3.4.0.CR1 --> 5 <hibernate-mapping package="com.jason.hibernate.entities.foreign.one2one"> 6 <class name="Manager" table="MANAGER"> 7 8 <id name="mgrId" type="java.lang.Integer"> 9 <column name="MGR_ID" /> 10 <generator class="native" /> 11 </id> 12 13 <property name="mgrName" type="java.lang.String"> 14 <column name="MGR_NAME" /> 15 </property> 16 17 18 <!-- 映射 1-1 的关联关系：在对应的数据表中已经有外键了，当前持久化类使用 one-to-one 进行映射 19 需要使用one-to-one元素，该元素使用 property-ref 属性指定使用被关联实体主键以外的字段作为关联字段 20 --> 21 <one-to-one name="dept" class="Department" property-ref="mgr"></one-to-one> 22 </class> 23 24 </hibernate-mapping>
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://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> 5 <hibernate-configuration> 6 <session-factory> 7 <!-- hibernate 连接数据库的基本信息 --> 8 <property name="connection.username">root</property> 9 <property name="connection.password">zhangzhen</property> 10 <property name="connection.driver_class">com.mysql.jdbc.Driver</property> 11 <property name="connection.url">jdbc:mysql:///hibernate</property> 12 13 14 <!-- 配置hibernate 的节本信息 --> 15 <!-- hibernate 所使用的数据库方言 --> 16 <!--<property name="dialect">org.hibernate.dialect.MySQLInnoDBDialect</property>--> 17 <property name="dialect">org.hibernate.dialect.MySQLDialect</property> 18 <!-- 执行操作时是否在控制台打印SQL --> 19 <property name="show_sql">true</property> 20 21 <!-- 是否都SQL 进行格式化 --> 22 <property name="format_sql">true</property> 23 24 25 <!-- 指定自动生成数据表的策略 --> 26 <property name="hbm2ddl.auto">update</property> 27 28 <!-- 设置hibernate 的事务隔离级别 --> 29 <property name="connection.isolation">2</property> 30 31 32 <!-- 配置c3p0 --> 33 <property name="hibernate.c3p0.max_size">10</property> 34 <property name="hibernate.c3p0.min_size">5</property> 35 <property name="c3p0.acquire_increment">2</property> 36 <property name="c3p0.idle_test_period">2000</property> 37 <property name="c3p0.timeout">2000</property> 38 <property name="c3p0.max_statements">10</property> 39 <!-- 1-1 映射 --> 40 41 <mapping resource="com/jason/hibernate/entities/foreign/one2one/Manager.hbm.xml"/> 42 <mapping resource="com/jason/hibernate/entities/foreign/one2one/Department.hbm.xml"/> 43 44 45 </session-factory> 46 47 </hibernate-configuration>
HibernateTest
1 package com.jason.hibernate.entities.foreign.one2one;
2
3 import hibernate.helloworld.News;
4
5 import java.util.Date;
6
7 import org.hibernate.Hibernate;
8 import org.hibernate.Session;
9 import org.hibernate.SessionFactory;
10 import org.hibernate.Transaction;
11 import org.hibernate.cfg.Configuration;
12 import org.hibernate.service.ServiceRegistry;
13 import org.hibernate.service.ServiceRegistryBuilder;
14 import org.junit.After;
15 import org.junit.Before;
16 import org.junit.Test;
17
18 public class HibernateTest {
19
20 private SessionFactory sessionFactory;
21 private Session session;
22 private Transaction transaction;
23 @Test
24 public void test() {
25
26 // 1. 创建一个SessionFatory 对象
27 SessionFactory sessionFactory = null;
28
29 // 1) 创建Configuration 对象：对应hibernate 的基本配置信息 和 对象关系映射信息
30 Configuration configuration = new Configuration().configure();
31
32 // 2) 创建一个ServiceRegistry 对象：hibernate 4.x 新天添加的对象。
33 // hibernate 的任何配置 和 服务都需要在该对象中注册后才有效
34 ServiceRegistry serviceRegistry = new ServiceRegistryBuilder()
35 .applySettings(configuration.getProperties())
36 .buildServiceRegistry();
37
38 // sessionFactory = configuration.buildSessionFactory();
39 sessionFactory = configuration.buildSessionFactory(serviceRegistry);
40
41 // 2. 创建一个session 对象
42 Session session = sessionFactory.openSession();
43
44 // 3. 开启事物
45 Transaction transaction = session.beginTransaction();
46
47 // 4.执行保存操作
48 News news = new News("java", "jason", new Date(
49 new java.util.Date().getTime()));
50 session.save(news);
51
52 // 5.提交事物
53 transaction.commit();
54 // 6.关闭session
55 session.close();
56 // 7.关闭SessionFactory 对象
57 sessionFactory.close();
58 }
59
60 // 创建上述三个对象
61 @Before
62 public void init() {
63 Configuration configuration = new Configuration().configure();
64 ServiceRegistry serviceRegistry = new ServiceRegistryBuilder()
65 .applySettings(configuration.getProperties())
66 .buildServiceRegistry();
67
68 sessionFactory = configuration.buildSessionFactory(serviceRegistry);
69
70 session = sessionFactory.openSession();
71
72 transaction = session.beginTransaction();
73 }
74
75 // 关闭上述三个对象
76 @After
77 public void destroy() {
78 transaction.commit();
79 session.close();
80 sessionFactory.close();
81 }
82
83
84 @Test
85 public void testSave(){
86
87 Department department = new Department();
88 department.setDeptName("DEPT-AA");
89
90 Manager manager = new Manager();
91 manager.setMgrName("MGR-AA");
92
93
94 //设定关联关系
95 department.setMgr(manager);
96 manager.setDept(department);
97
98 //保存
99 //建议先保存没有外键列的那个对象，这样会减少update 语句
100 session.save(manager);
101 session.save(department);
102
103
104 }
105
106 @Test
107 public void testGet(){
108
109 //1.默认情况下对关联属性使用懒加载
110 Department dept = (Department) session.get(Department.class, 1);
111 System.out.println(dept.getDeptName());
112
113
114 //2.查询Manager 对象的连接条件应该是dept.manager_id = mgr.manager_id
115 //而不因该是 manager0_.MGR_ID=department1_.DEPT_ID
116 Manager mgr = dept.getMgr();
117 System.out.println(mgr);
118 }
119
120
121 @Test
122 public void testGet2(){
123
124 //在查询没有外键的实体对象，使用的是左外连接查询，一并查询出其关联的对象，并已经进行初始化
125 Manager manager = (Manager) session.get(Manager.class, 1);
126 System.out.println(manager);
127
128 System.out.println(manager.getDept().getDeptName());
129
130 }
131
132
133
134
135 }
时间： 2024-10-12 19:18:49