标签：style blog color java 使用 os io strong
一对一单向外键关联
1.建Husband实体类和Wife实体类，添加Annotation注解，如下
@Entity
public class Husband {
private int id;
private String name;
private Wife wife;
@Id
@GeneratedValue
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;
}
@OneToOne //Husband和Wife是一对一的关系
public Wife getWife() {
return wife;
}
public void setWife(Wife wife) {
this.wife = wife;
}
}
@Entity
public class Wife {
private int id;
private String name;
@Id
@GeneratedValue
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;
}
}
2.在hibernate.cfg.xml中添加mapping语句
<mapping class="com.hibernate.model.Husband"/> <mapping class="com.hibernate.model.Wife"/>
3.建Junit测试类
public class ORMappingTest {
@Test
public void test() {
//生成表，输出建表语句
new SchemaExport(new Configuration().configure()).create(true, true);
}
}
程序至此结束，运行程序，在数据库中生成Husband表和Wife表，并在控制台输出建表语句。
Husband表中会自动生成属性名为“wife_id”的外键，参考表为Wife表。
如果想要使用自定义的外键属性名，可对Husband实体类的getWife方法添加Annotation注解，如下：
@OneToOne //Husband和Wife是一对一的关系
@JoinColumn(name="wifeId") // java默认生成的外键属性名为wife_id.设置此项后，可以任意设定其属性名，此处设置为wifeId.
public Wife getWife() {
return wife;
}
一对一双向外键关联
1.建Husband实体类和Wife实体类，添加Annotation注解
Husband类同上，只需在Wife类中增加一个Husband类型的变量，并添加@OneToOne注解即可，如下
@Entity
public class Wife {
private int id;
private String name;
private Husband husband; //建一个Husband类型的变量，并生成setter和getter方法
@Id
@GeneratedValue
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;
}
@OneToOne(mappedBy="wife") //"wife"指的是Husband类中的private Wife wife;
public Husband getHusband() {
return husband;
}
public void setHusband(Husband husband) {
this.husband = husband;
}
}
凡是双向关联，必设mappedBy
2.在hibernate.cfg.xml中添加mapping语句----同上
3.建Junit测试类----同上
程序至此结束，运行程序，在数据库中生成Husband表和Wife表，并在控制台输出建表语句。
联合主键
联合主键（3种方式）
将组件类注解为@Embeddable，并将组件的属性注解为@Id (不常用)
将组件的属性注解为@EmbeddedId
将实体类注解为@IdClass(组件类.class)，并将该实体类中所有属于主键的属性都注解为@Id
示例：建Wife表，属性有id，name，age。其中id和name为联合主键
1.建组件类WifePK
/*
* 建立组件类WifePK
* 需实现Serializable接口，此接口用于把当前类的接口进行序列化
* 需重写equals()和hashCode()方法，以保证对象的唯一性
*
**/
public class WifePK implements java.io.Serializable{
private int id;
private String name;
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;
}
@Override
public boolean equals(Object o){
if(o instanceof WifePK){
WifePK pk = (WifePK) o;
if(this.id == pk.getId() && this.name.equals(pk.getName())){
return true;
}
}
return false;
}
@Override
public int hashCode(){
return this.name.hashCode();
}
}
2.建实体类Wife
第二种方式注解，@EmbeddedId
@Entity
public class Wife {
private WifePK pk; //增加WifePK类型的变量，并添加getter和setter方法
private int age;
@EmbeddedId //将其注解为联合主键
public WifePK getPk() {
return pk;
}
public void setPk(WifePK pk) {
this.pk = pk;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
第三种方式注解，@IdClass
@Entity
@IdClass(WifePK.class) //将实体类注解为@IdClass
public class Wife {
private int id;
private String name;
private int age;
@Id //将该实体类中属于主键的属性注解为@Id
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@Id //将该实体类中属于主键的属性注解为@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;
}
}
3.写Junit测试类
第二种方式注解，@EmbeddedId
public class WifeTest {
private static SessionFactory sf = null;
@BeforeClass
public static void beforeClass() {
sf = new Configuration().configure().buildSessionFactory();
}
@AfterClass
public static void afterClass() {
sf.close();
}
@Test
public void test() {
WifePK pk = new WifePK();
pk.setId(1);
pk.setName("zhangsan");
Wife wife = new Wife();
wife.setPk(pk);
wife.setAge(32);
Session session = sf.getCurrentSession();
session.beginTransaction();
session.save(wife);
session.getTransaction().commit();
}
}
第三种方式注解，@IdClass，只需修改其test()方法，如下：
@Test
public void test() {
Wife wife = new Wife();
wife.setId(1);
wife.setName("zhangsan");
wife.setAge(32);
Session session = sf.getCurrentSession();
session.beginTransaction();
session.save(wife);
session.getTransaction().commit();
}
程序至此结束，运行程序，在数据库中生成Wife表，id和name为主键，并将对象wife存入Wife表。
联合主键关联
示例：
建Husband表，属性有id和name
建Wife表，属性有id，name，age。其中id和name为联合主键
设置联合主键关联，在Husband表中生成属性名为wife_id和wife_name的外键，分别参考Wife表中的id和name
1.建Husband实体类、Wife实体类和WifePK组件类，添加Annotation注解
Husband类，同上
WifePK类，同上
Wife类，同“联合主键”部分第三种方式注解的Wife实体类
2.在hibernate.cfg.xml中添加mapping语句----同上
3.建Junit测试类ORMappingTest----同上
程序至此结束，运行程序，在数据库中生成Husband表和Wife表，并在控制台输出建表语句。
Husband表中会自动生成属性名为“wife_id”和“wife_name”的外键，参考表为Wife表。
如果想要使用自定义的外键属性名，可对Husband实体类的getWife方法添加Annotation注解，如下：
@OneToOne
@JoinColumns(
{
@JoinColumn(name="wifeId",referencedColumnName="id"),
@JoinColumn(name="wifeName",referencedColumnName="name")
}
)
public Wife getWife() {
return wife;
}标签：style blog color java 使用 os io strong
原文地址：http://www.cnblogs.com/weilunhui/p/3895852.html
