Hibernate基础之6：联合主键@EmbeddedId

一：联合主键类

联合主键就是靠多个属性一起来决定主键
所以要新建主键类，其中要实现
1.Serializable //主键需要传递
2.equals(Object o) //靠主键区分pk，所以必须

3.hashCode()//根据pk的哈希码去查找，所以必须

public class TeacherPK implements Serializable{	private int id;	private String name;//根据这两项属性联合生成主键		public boolean equals(Object o) //靠主键区分pk，所以必须	{		if(o instanceof  TeacherPK)		{			TeacherPK pk = (TeacherPK)o;//强转			if(this.id == pk.getId() && this.name.equals(pk.getName()))			{				return true;//id和name都分别相等，才是同一主键			}		}		return false;//其余所有情况都返回false	}	public int hashCode()//根据pk的哈希码去查找，所以必须	{		return this.name.hashCode();		}			//setter&getter

二：Annotation标注

1.TeacherPK上写@Embeddable
聚合的getPk()上写@Id

2.getPk()上写@EmbeddedId

3.实体上@IdClass(value=TeacherPK.class)
name和id上都要写@Id

@Entity@Table(name="t_Teacher")public class Teacher {		private TeacherPK pk;//聚合联合主键	private int age;	private Date birthday;	private String secret;	private Grade grade;	//setter&getter	@EmbeddedId //联合主键的getPK()方法上写 EmbeddedId	public TeacherPK getPk() {		return pk;	}

三：JUnit测试

		Session session = HibernateUtil.getSessionFactory().getCurrentSession();        session.beginTransaction();                        TeacherPK pk = new TeacherPK();//组装联合主键        pk.setId(250);        pk.setName("张三");		        Teacher t = new Teacher();        t.setPk(pk); //set联合主键		t.setAge(0);		t.setBirthday(new Date());		t.setGrade(Grade.A);		        session.save(t);        session.getTransaction().commit();        HibernateUtil.getSessionFactory().close();      

DEBUG SchemaUpdate:226 - create table t_Teacher (id number(10,0) not null, name varchar2(255 char) not null, age number(10,0) not null, birthday date, grade varchar2(255 char), primary key (id, name))