hibernate联合主键的三种注解做法

1.给组件类加上@Embeddable注解，给实体类的主键属性加上@Id

如组件类如下写：

package vo;

import java.io.Serializable;

import javax.persistence.Embeddable;

@Embeddable

public class StudentPK implements Serializable{

private int sid;

private String sname;

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;

}

@Override

public int hashCode() {

final int prime = 31;

int result = 1;

result = prime * result + sid;

result = prime * result + ((sname == null) ? 0 : sname.hashCode());

return result;

}

@Override

public boolean equals(Object obj) {

if (this == obj)

return true;

if (obj == null)

return false;

if (getClass() != obj.getClass())

return false;

StudentPK other = (StudentPK) obj;

if (sid != other.sid)

return false;

if (sname == null) {

if (other.sname != null)

return false;

} else if (!sname.equals(other.sname))

return false;

return true;

}





}

而实体类如下写

package vo;

import javax.persistence.Embedded;

import javax.persistence.EmbeddedId;

import javax.persistence.Entity;

@Entity

public class Student {

private StudentPK pk;

private int age;





public int getAge() {

return age;

}

public void setAge(int age) {

this.age = age;

}

@Id

public StudentPK getPk() {

return pk;

}

public void setPk(StudentPK pk) {

this.pk = pk;

}



}

2.第二种注解写法：直接在实体类的主键属性上加@EmbededId即可

3.第三种写法：实体类还需要加上主键属性sid,sname，只不过在这两个属性上都加上@Id，在实体类上边加上@IdClass（value=StudentPK.class）