Hiberante学习08---基于Annotation配置的一对一单向外键关联

注意，要在外键字段上加

@OneToOne(cascade=CascadeType.ALL)

@JoinColumn(name=”pid”,unique=”true”)

保存时先保存外键对象，再保存主对象

前提是加入相应的jar包，主要是多了一个3.8版本的junit.jar..
步聚如下：
1、pojo类，Students.java

package com.demo.pojo.dxwj;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;

@Entity
public class Students {
private int sid;
private String sname;
private IdCard cardId;

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
public int getSid() {
return sid;
}
public void setSid(int sid) {
this.sid = sid;
}
public String getSname() {
return sname;
}
public void setSname(String sname) {
this.sname = sname;
}

@OneToOne(cascade=CascadeType.ALL)
@JoinColumn(name="pid",unique=true)
public IdCard getCardId() {
return cardId;
}
public void setCardId(IdCard cardId) {
this.cardId = cardId;
}

}

Idcard.java类

package com.demo.pojo.dxwj;

import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
public class IdCard {

private String pid;
private String province;

@Id
public String getPid() {
return pid;
}
public void setPid(String pid) {
this.pid = pid;
}
public String getProvince() {
return province;
}
public void setProvince(String province) {
this.province = province;
}

}

2、Hibernate配置文件，这里注意的是有用到getCurrentSession和SchemaExport,所以需要在配置文件中加入相应的配置，保存时先保存外键对象，再保存主对象

<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
<session-factory name="mysql">

<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="connection.url">jdbc:mysql://localhost:3306/test</property>
<property name="connection.username">root</property>
<property name="connection.password"></property>

<property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>

<!-- sessionFactory.getCurrentSession用到的配置文件 -->
<property name="hibernate.current_session_context_class">thread</property>
<!-- 有四个值create,create-drop,update,validate -->
<property name="hbm2ddl.auto">update</property>

<property name="show_sql">true</property>

<mapping class="com.demo.pojo.dxwj.Students"/>
<mapping class="com.demo.pojo.dxwj.IdCard"/>
</session-factory>
</hibernate-configuration>

3、测试类，先执行testSchemaExport测试方法，以生成数据库中的表，然后在执行testSave测试方法，以插入数据库

package com.demo.pojo.dxwj;

import junit.framework.TestCase;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.tool.hbm2ddl.SchemaExport;

public class TestStudent extends TestCase{

private SessionFactory sf;

public void testSave()
{
sf = new AnnotationConfiguration().configure().buildSessionFactory();
Session s = sf.getCurrentSession();
Transaction tx = s.beginTransaction();
tx.begin();
IdCard idCard = new IdCard();
idCard.setPid("11111111");
idCard.setProvince("fujian");
Students student = new Students();
//因为是主键类型是Auto的，所以不用setId..
student.setSname("zhangsan");
student.setCardId(idCard);
//先保存外键所在的对象
s.save(idCard);
//再保存主键所在的对象
s.save(student);

tx.commit();
}

public void testSchemaExport()
{
SchemaExport se = new SchemaExport(new AnnotationConfiguration().configure());
se.create(true, true);
}

protected void setUp() throws Exception {
System.out.println("setUp()....");
}

protected void tearDown() throws Exception {
System.out.println("tearDown()....");
}

}