比如一对夫妻，丈夫有id,name；妻子有id，name。增加一对一单向外键关联一般有以下几种方法：
1.在husband中增加一个外键，foreign key
2.在husband中增加字段wife_id,wife_id参照wife的id。以wife为主导，必须wife里有id才能参照
3.在wife中增加一个外键，foreign key
4.在wife中增加字段husband_id,husband_id参照husband的id。以hunsband为主导，必须hunsband里有id才能参照
5.增加中间表——关联表
数据库设计一般两种：主键关联，单向外键关联
示例代码：
husband类
package com.zzk.hibernate.model;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;
@Entity
public class Husband {
private int id;
private String name;
private Wife wife;//对象引用，建立关联
@Id
@GeneratedValue
public int getId() {
return id;
}
public String getName() {
return name;
}
@OneToOne
public Wife getWife() {
return wife;
}
public void setId(int id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}
public void setWife(Wife wife) {
this.wife = wife;
}
}
wife类
package com.zzk.hibernate.model;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
@Entity
public class Wife {
private int id;
private String name;
@Id
@GeneratedValue
public int getId() {
return id;
}
public String getName() {
return name;
}
public void setId(int id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}
}
JUNIT测试生成建表语句的方法：
@Test
public void testSchemaExport() {
new SchemaExport(new AnnotationConfiguration().configure()).create(false, true);
}
LOG4J输出：
11:07:55,366 INFO org.hibernate.tool.hbm2ddl.SchemaExport:226 - Running hbm2ddl schema export
11:07:55,369 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:242 - import file not found: /import.sql
11:07:55,369 INFO org.hibernate.tool.hbm2ddl.SchemaExport:251 - exporting generated schema to database
11:07:55,559 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
alter table Husband
drop
foreign key FKAEEA401B4AFE23AB
11:07:55,626 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:362 - Unsuccessful: alter table Husband drop foreign key FKAEEA401B4AFE23AB
11:07:55,626 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:363 - Table 'hibernate.husband' doesn't exist
11:07:55,627 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
drop table if exists Husband
11:07:55,648 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
drop table if exists Wife
11:07:55,652 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
create table Husband (
id integer not null auto_increment,
name varchar(255),
wife_id integer,
primary key (id)
)
11:07:55,743 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
create table Wife (
id integer not null auto_increment,
name varchar(255),
primary key (id)
)
11:07:55,818 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
alter table Husband
add index FKAEEA401B4AFE23AB (wife_id),
add constraint FKAEEA401B4AFE23AB
foreign key (wife_id)
references Wife (id)
11:07:56,040 INFO org.hibernate.tool.hbm2ddl.SchemaExport:268 - schema export complete
然后为了将wife_id改为wifeId，可以对husband类作如下处理：
package com.zzk.hibernate.model;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;
@Entity
public class Husband {
private int id;
private String name;
private Wife wife;//对象引用，建立关联
@Id
@GeneratedValue
public int getId() {
return id;
}
public String getName() {
return name;
}
@OneToOne
@JoinColumn (name="wifeId")
public Wife getWife() {
return wife;
}
public void setId(int id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}
public void setWife(Wife wife) {
this.wife = wife;
}
}
运行JUNIT测试方法，LOG4J打印的建表语句即变为：
11:27:11,113 INFO org.hibernate.tool.hbm2ddl.SchemaExport:226 - Running hbm2ddl schema export
11:27:11,116 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:242 - import file not found: /import.sql
11:27:11,116 INFO org.hibernate.tool.hbm2ddl.SchemaExport:251 - exporting generated schema to database
11:27:11,303 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
alter table Husband
drop
foreign key FKAEEA401BCC07428E
11:27:11,393 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:362 - Unsuccessful: alter table Husband drop foreign key FKAEEA401BCC07428E
11:27:11,394 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:363 - Error on rename of '.\hibernate\husband' to '.\hibernate\#sql2-8f0-f' (errno: 152)
11:27:11,395 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
drop table if exists Husband
11:27:11,418 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
drop table if exists Wife
11:27:11,445 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
create table Husband (
id integer not null auto_increment,
name varchar(255),
wifeId integer,
primary key (id)
)
11:27:11,505 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
create table Wife (
id integer not null auto_increment,
name varchar(255),
primary key (id)
)
11:27:11,579 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
alter table Husband
add index FKAEEA401BCC07428E (wifeId),
add constraint FKAEEA401BCC07428E
foreign key (wifeId)
references Wife (id)
11:27:11,715 INFO org.hibernate.tool.hbm2ddl.SchemaExport:268 - schema export complete
另外一种方法配置：
student类
package com.zzk.hibernate.model;
public class Student {
private int id;
private String name;
private int age;
private String sex;
private boolean good;
public boolean isGood() {
return good;
}
public void setGood(boolean good) {
this.good = good;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
}
StuIdCard类
package com.zzk.hibernate.model;
public class StuIdCard {
private int id;
private String num;
private Student student;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getNum() {
return num;
}
public void setNum(String num) {
this.num = num;
}
public Student getStudent() {
return student;
}
public void setStudent(Student student) {
this.student = student;
}
}
StuIdCard.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.zzk.hibernate.model.StuIdCard">
<id name="id">
<generator class="native"></generator>
</id>
<property name="num"/>
<many-to-one name="student" column="studentId" unique="true"></many-to-one>
</class>
</hibernate-mapping>
Student.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.zzk.hibernate.model.StuIdCard">
<id name="id">
<generator class="native"></generator>
</id>
<property name="num"/>
<many-to-one name="student" column="studentId" unique="true"></many-to-one>
</class>
</hibernate-mapping>
hibernate.cfg.xml增加如下：
<mapping resource="com/zzk/hibernate/model/Student.hbm.xml"/>
<mapping resource="com/zzk/hibernate/model/StuIdCard.hbm.xml"/>
JUNIT单元测试：
@Test
public void testSchemaExport() {
new SchemaExport(new AnnotationConfiguration().configure()).create(false, true);
}
输出LOG4J的一些建表语句如下：
15:03:29,397 INFO org.hibernate.tool.hbm2ddl.SchemaExport:226 - Running hbm2ddl schema export
15:03:29,401 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:242 - import file not found: /import.sql
15:03:29,401 INFO org.hibernate.tool.hbm2ddl.SchemaExport:251 - exporting generated schema to database
15:03:31,082 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
alter table Husband
drop
foreign key FKAEEA401BCC07428E
15:03:31,880 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
alter table StuIdCard
drop
foreign key FKD3A449FF7E0CA1A0
15:03:31,934 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:362 - Unsuccessful: alter table StuIdCard drop foreign key FKD3A449FF7E0CA1A0
15:03:31,934 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:363 - Table 'hibernate.stuidcard' doesn't exist
15:03:31,934 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
drop table if exists Husband
15:03:31,960 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
drop table if exists StuIdCard
15:03:31,970 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
drop table if exists Student
15:03:32,045 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
drop table if exists Wife
15:03:32,132 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
create table Husband (
id integer not null auto_increment,
name varchar(255),
wifeId integer,
primary key (id)
)
15:03:32,214 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
create table StuIdCard (
id integer not null auto_increment,
num varchar(255),
studentId integer unique,
primary key (id)
)
15:03:32,306 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
create table Student (
id integer not null auto_increment,
name varchar(255),
age integer,
sex varchar(255),
good char(1),
primary key (id)
)
15:03:32,382 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
create table Wife (
id integer not null auto_increment,
name varchar(255),
primary key (id)
)
15:03:32,446 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
alter table Husband
add index FKAEEA401BCC07428E (wifeId),
add constraint FKAEEA401BCC07428E
foreign key (wifeId)
references Wife (id)
15:03:32,722 DEBUG org.hibernate.tool.hbm2ddl.SchemaExport:377 -
alter table StuIdCard
add index FKD3A449FF7E0CA1A0 (studentId),
add constraint FKD3A449FF7E0CA1A0
foreign key (studentId)
references Student (id)
15:03:32,916 INFO org.hibernate.tool.hbm2ddl.SchemaExport:268 - schema export complete
时间： 2024-10-22 20:33:41