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

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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;@Entitypublic 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@Idpublic 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;@Entitypublic class Students {private int sid;private String sname;private IdCard cardId;@Idpublic 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()....");}}