一对一关联有两种实现方式：一种是共享的主键关联，另一种是一对一的外键关联
1、共享的主键关联：让两个对象具有共同的主键值，以表明他们之间的一一对应关系。
Person.java类
1 public class Person implements java.io.Serializable {
2
3 // Fields
4
5 private Integer id;
6 private String name;
7 private Idcard idcard;
8
9 // Constructors
10
11 /** default constructor */
12 public Person() {
13 }
14
15 /** full constructor */
16 public Person(String name) {
17 this.name = name;
18 }
19
20 // Property accessors
21
22 public Integer getId() {
23 return this.id;
24 }
25
26 public void setId(Integer id) {
27 this.id = id;
28 }
29
30 public String getName() {
31 return this.name;
32 }
33
34 public void setName(String name) {
35 this.name = name;
36 }
37 public Idcard getIdcard() {
38 return idcard;
39 }
40
41 public void setIdcard(Idcard idcard) {
42 this.idcard = idcard;
43 }
44 }
Idcard.java类
1 public class Idcard implements java.io.Serializable {
2
3 // Fields
4
5 private Integer id;
6 private String idcardno;
7 private Person person;
8
9 // Constructors
10
11 /** default constructor */
12 public Idcard() {
13 }
14
15 /** full constructor */
16 public Idcard(String idcardno) {
17 this.idcardno = idcardno;
18 }
19
20 // Property accessors
21
22 public Integer getId() {
23 return this.id;
24 }
25
26 public void setId(Integer id) {
27 this.id = id;
28 }
29
30 public String getIdcardno() {
31 return this.idcardno;
32 }
33
34 public void setIdcardno(String idcardno) {
35 this.idcardno = idcardno;
36 }
37
38 public Person getPerson() {
39 return person;
40 }
41
42 public void setPerson(Person person) {
43 this.person = person;
44 }
45
46 }
Person.hbm.xml
1 <?xml version="1.0" encoding="utf-8"?> 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" 3 "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> 4 <!-- 5 Mapping file autogenerated by MyEclipse Persistence Tools 6 --> 7 <hibernate-mapping> 8 <class name="com.db.entity.Person" table="person" catalog="mydb"> 9 <id name="id" type="java.lang.Integer"> 10 <column name="id" /> 11 <generator class="native" /> 12 </id> 13 <property name="name" type="java.lang.String"> 14 <column name="name" length="30" /> 15 </property> 16 <one-to-one name="idcard" class="com.db.entity.Idcard" cascade="all" /> 17 </class> 18 </hibernate-mapping>
Idcard.hbm.xml
1 <hibernate-mapping> 2 <class name="com.db.entity.Idcard" table="idcard" catalog="mydb"> 3 <id name="id" type="java.lang.Integer"> 4 <column name="id" /> 5 <generator class="foreign"> 6 <param name="property">person</param> 7 </generator> 8 </id> 9 <one-to-one name="person" constrained="true" class="com.db.entity.Person"></one-to-one> 10 <property name="idcardno" type="java.lang.String"> 11 <column name="idcardno" length="20" /> 12 </property> 13 </class> 14 </hibernate-mapping>
bibernate.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 <!-- Generated by MyEclipse Hibernate Tools. --> 6 <hibernate-configuration> 7 8 <session-factory> 9 <property name="dialect"> 10 org.hibernate.dialect.MySQLDialect 11 </property> 12 <property name="connection.url"> 13 jdbc:mysql://localhost:3306/mydb 14 </property> 15 <property name="connection.username">root</property> 16 <property name="connection.password">123456</property> 17 <property name="connection.driver_class"> 18 com.mysql.jdbc.Driver 19 </property> 20 <property name="myeclipse.connection.profile"> 21 MyDBAccount 22 </property> 23 <mapping resource="com/db/entity/Idcard.hbm.xml" /> 24 <mapping resource="com/db/entity/Person.hbm.xml" /> 25 </session-factory> 26 27 </hibernate-configuration>
测试代码：
1 public class TestOneOne {
2
3 public static void main(String[] args) {
4 // TODO Auto-generated method stub
5
6 Session session=null;
7 session=HibernateSessionFactory.getSession();
8 session.beginTransaction();
9 Idcard idcard=new Idcard();
10 idcard.setIdcardno("2345678901");
11 Person person=new Person();
12 person.setName("Lily");
13 person.setIdcard(idcard);
14 idcard.setPerson(person);
15 session.save(person);
16 session.save(idcard);
17 session.getTransaction().commit();
18
19 }
20
21 }
2、一对一的外键关联：外键关联，本来是用于多对一的配置，但是加上唯一的限制之后（采用<many-to-one>标签来映射，指定多的一端unique为true，这样就限制了多的一端的多重性为一），也可以用来表示一对一关联关系，其实它就是多对一的特殊情况。
首先在表idcard中新添加一列pid用于共享数据
Person.java类
1 public class Person implements java.io.Serializable {
2
3 // Fields
4
5 private Integer pid;
6 private String name;
7 private Idcard idcard;
8
9 // Constructors
10
11 /** default constructor */
12 public Person() {
13 }
14
15 /** full constructor */
16 public Person(String name) {
17 this.name = name;
18 }
19
20 // Property accessors
21
22 public Integer getPid() {
23 return this.pid;
24 }
25
26 public void setPid(Integer pid) {
27 this.pid = pid;
28 }
29
30 public String getName() {
31 return this.name;
32 }
33
34 public void setName(String name) {
35 this.name = name;
36 }
37 public Idcard getIdcard() {
38 return idcard;
39 }
40
41 public void setIdcard(Idcard idcard) {
42 this.idcard = idcard;
43 }
44 }
idcard.java类
1 public class Idcard implements java.io.Serializable {
2
3 // Fields
4
5 private Integer iid;
6 private String idcardno;
7 private Person person;
8
9 // Constructors
10
11 /** default constructor */
12 public Idcard() {
13 }
14
15 /** full constructor */
16 public Idcard(String idcardno) {
17 this.idcardno = idcardno;
18 }
19
20 // Property accessors
21
22 public Integer getIid() {
23 return this.iid;
24 }
25
26 public void setIid(Integer iid) {
27 this.iid = iid;
28 }
29
30 public String getIdcardno() {
31 return this.idcardno;
32 }
33
34 public void setIdcardno(String idcardno) {
35 this.idcardno = idcardno;
36 }
37
38 public Person getPerson() {
39 return person;
40 }
41
42 public void setPerson(Person person) {
43 this.person = person;
44 }
45
46 }
Person.hbm.xml
1 <hibernate-mapping> 2 <class name="com.db.entity.Person" table="person" catalog="mydb"> 3 <id name="pid" type="java.lang.Integer"> 4 <column name="pid" /> 5 <generator class="native" /> 6 </id> 7 <property name="name" type="java.lang.String"> 8 <column name="name" length="30" /> 9 </property> 10 <one-to-one name="idcard" class="com.db.entity.Idcard" property-ref="person"></one-to-one> 11 </class> 12 </hibernate-mapping>
Idcard.hbm.xml
1 <hibernate-mapping> 2 <class name="com.db.entity.Idcard" table="idcard" catalog="mydb"> 3 <id name="iid" type="java.lang.Integer"> 4 <generator class="native"> 5 </generator> 6 </id> 7 <many-to-one name="person" column="pid" class="com.db.entity.Person" 8 cascade="save-update" unique="true"></many-to-one> 9 <property name="idcardno" type="java.lang.String"> 10 <column name="idcardno" length="20" /> 11 </property> 12 </class> 13 </hibernate-mapping>
bibernate.cfg.xml文件和测试代码同上。
如果使用注解映射外键，则注解如下：
Idcard.java类
1 public class Idcard implements java.io.Serializable {
2
3 // Fields
4 private Person person;
5
6 @OneToOne
7 @JoinColumn(name="pid")
8 public Person getPerson() {
9 return person;
10 }
11
12 public void setPerson(Person person) {
13 this.person = person;
14 }
15
16 }
Person.java类
1 public class Person implements java.io.Serializable {
2
3 // Fields
4 private Idcard idcard;
5
6 @OneToOne(mappedBy="person")
7 public Idcard getIdcard() {
8 return idcard;
9 }
10
11 public void setIdcard(Idcard idcard) {
12 this.idcard = idcard;
13 }
14 }
时间： 2024-10-05 19:15:49