一对一、一对多、多对多的配置

一对一

基于注解的方式：

?hibernate中一对一的关联有两种方式：一种是采用外键关联，另外一种是采用主键关联。

??一个丈夫(husband)对应一个妻子(wife)，主要目标是在存储丈夫或者妻子时，关联的对象也被存储。具体代码如下：

??husband类：?

package cn.edu.dlnu.resources.model.entity;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.PrimaryKeyJoinColumn;

@Entity
public class Husband {
?private int id;
?private String name;
?private Wife wife;
?@Id
?@GeneratedValue //主键生成器
?public int getId() {
??return id;
?}
?public String getName() {
??return name;
?}
?@OneToOne(cascade=CascadeType.ALL)
?@PrimaryKeyJoinColumn//这个注解只能写在主(生成ID)的一端
?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 cn.edu.dlnu.resources.model.entity;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import org.hibernate.annotations.GenericGenerator;
import org.hibernate.annotations.Parameter;

@Entity
public class Wife {
?private int id;
?private String name;
?private Husband husband;
?
?@Id
?@GenericGenerator(name ="pkGenerator",strategy="foreign" ,parameters={@Parameter(name="property",value="husband")})
????@GeneratedValue(generator="pkGenerator")

//wife的ID是根据husband的ID来赋值的，这里需要设置ID生成器的策略为foreign，参数中指定wife的ID是使用husband对象中的ID
?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 void setHusband(Husband husband) {
??this.husband = husband;
?}
?@OneToOne(cascade=CascadeType.ALL, mappedBy="wife")

?public Husband getHusband() {
??return husband;
?}
}
??OneToOnePKTest类：

package cn.edu.dlnu.resources.model.entity;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.tool.hbm2ddl.SchemaExport;
import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.Test;

import cn.edu.dlnu.resources.model.entity.Husband;
import cn.edu.dlnu.resources.model.entity.Wife;

public class OneToOnePKTest {
?private static SessionFactory sessionFactory;
?
?@BeforeClass
?public static void beforeClass() {
???sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
?}
?@AfterClass
?public static void afterClass() {
??sessionFactory.close();
?}
?
?@Test
?public void testSave(){
??Session s = sessionFactory.getCurrentSession();
??s.beginTransaction();
??
??Husband h = new Husband();
??Wife w = new Wife();
??w.setName("w");
??h.setName("h");

??h.setWife(w);
??w.setHusband(h);
??s.save(w);
??s.getTransaction().commit();
?}

@Test
?public void testSchemaExport() {
??new SchemaExport(new AnnotationConfiguration().configure()).create(false, true);
?}
?public static void main(String[] args) {
??beforeClass();
??new OneToOnePKTest().testSave();
??afterClass();
?}
}

hibernate生成的数据库表：create table Husband (
????????id integer not null auto_increment,
????????name varchar(255),
????????primary key (id)
????)；

create table Wife (
????????id integer not null,
????????name varchar(255),
????????primary key (id)
????)
运行testSave()，方法后数据库中husband 与 wife表中记录的主键一致。