Hiberante学习10---基于Annotation配置的一对一双向外键关联

在单向外键关联中，我们是在student类中保存idcard的引用，这里在双向外键关联中是互相包含对方的引用，但这样子会造成对象不能保存，

所以要设置如下属性：

@OneToOne(mappedBy=”stu”)//设置将控制权交给哪一方？
双向关联，必须设置mappedBy属性，因为双向关联只能交给一方去控制，不可能在双方都设置外键保存关联关系，否则双方都无法保存。

步骤:
1、pojo类，这里我们将控制权交给Idcard类

package com.demo.pojo.sxwj;

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

@Entity
public class IdCard {

private String pid;
private String province;
private Students stu;

@OneToOne(cascade=CascadeType.ALL)
@JoinColumn(name="sid")
public Students getStu() {
return stu;
}
public void setStu(Students stu) {
this.stu = stu;
}
//不指定主键生成策略时，默认为GeneratedValue.AUTO
@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;
}

}

package com.demo.pojo.sxwj;

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

@Entity
public class Students {
private int sid;
private String sname;
private IdCard cardId;
@Id
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(mappedBy="stu")
public IdCard getCardId() {
return cardId;
}
public void setCardId(IdCard cardId) {
this.cardId = cardId;
}

}

2、配置文件没有变
3、测试类

package com.demo.pojo.sxwj;

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 TestStudentByAnno extends TestCase{

private SessionFactory sf;

public void testSave()
{
sf = new AnnotationConfiguration().configure().buildSessionFactory();
Session s = sf.getCurrentSession();
Transaction tx = s.beginTransaction();
tx.begin();

Students student = new Students();
student.setSname("zhangsan");

IdCard idCard = new IdCard();
idCard.setPid("11111111");
idCard.setProvince("fujian");
idCard.setStu(student);

s.save(student);
s.save(idCard);

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()....");
}

}