hibernate的复合/联合主键出错

Question

数据库用的是oracle
报错:Exception in thread "main" java.lang.NullPointerException这一般是oracle部分建表的问题还是hibernate部分配置出问题

Answer 1

package student;import java.io.Serializable;public class Studentpk implements Serializable {
private String name;
private String psw;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPsw() {
return psw;
}
public void setPsw(String psw) {
this.psw = psw;
}
}
<hr />
package student;public class Student {
private Studentpk stupk;
private Integer age;
private Integer photo;

public Studentpk getStupk() {
return stupk;
}
public void setStupk(Studentpk stupk) {
this.stupk = stupk;
} 
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public Integer getPhoto() {
return photo;
}
public void setPhoto(Integer photo) {
this.photo = photo;
}
}
<hr />
<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-mapping PUBLIC
          "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
          "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="student.Student" table="teststudent">
<composite-id name="stupk" class="student.Studentpk">
<key-property name="name" type="java.lang.String" column="name"></key-property>
<key-property name="psw" type="java.lang.String" column="psw"></key-property>
</composite-id>
<property name="age" type="java.lang.Integer" column="age"></property>
<property name="photo" type="java.lang.Integer" column="photo"></property>
</class>
</hibernate-mapping>
<hr />
package test;import org.hibernate.Session;
import student.Student;
import student.Studentpk;
import util.HibernateSessionFactory;public class Test {
public static void main(String[] args) {
Session session=HibernateSessionFactory.getSession();
Studentpk stupk=new Studentpk();
Student stu=(Student)session.get(Student.class, stupk);
System.out.println(stu.getAge());
 
HibernateSessionFactory.closeSession();
}
}
<hr />
create table teststudent(
  2   name varchar(50) primary key,
  3   psw varchar(20),
  4   age integer,
  5   photo integer);insert into teststudent values('arisu','abc',7,123);就这样了,不知道错在那里

Answer 2

Studentpk stupk=new Studentpk();stupk对象没有初始化，所以查不到东西！得到的stu是NULL，所以System.out.println(stu.getAge())里面getAge报空指针

Answer 3

public class Test {
public static void main(String[] args) {
Session session=HibernateSessionFactory.getSession();
Studentpk stupk=new Studentpk();
Student stu=(Student)session.get(Student.class, stupk);
System.out.println(stu.getAge());
 
HibernateSessionFactory.closeSession();
}
}
有初始,表里也有数据