问题是你试图调用实例方法createStudent()
从静态上下文中main()
。如果你改变你的createStudent()
方法是静态的,你应该可以开始:
public static Student createStudent(String student_id, Date dob, String gender, String nationality, Type_Name name) {
// ... And so on
}
EDIT:OP指出,仅此更改就给他在访问变量时带来了另一个错误em
and emf
。要解决这个问题,您需要创建这些变量static
, too:
static EntityManager em;
static EntityManagerFactory emf;
那时,班级中的所有内容都是静态的。假设这是一个简单的一次性或示例——我很乐意假设,因为该类被称为Main
——让一切都静态就可以了。总而言之,代码如下所示:
package grade_db;
import bean.Student;
import bean.Type_Name;
import bean.University;
import java.util.Date;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
/**
*
* @author Sam
*/
public class Main {
static EntityManager em;
static EntityManagerFactory emf;
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
EntityManagerFactory emf = Persistence.createEntityManagerFactory("db/grades.odb");
EntityManager em;
em = emf.createEntityManager();
createStudent("stu00001", new Date(631152000000)), "m", "WB", new Type_Name("Bob", "", "Smith"));
em.close();
emf.close();
}
public static Student createStudent(String student_id, Date dob, String gender, String nationality, Type_Name name){
Student stu = new Student();
stu.setDob(dob);
stu.setGender(gender);
stu.setName(name);
stu.setNationality(nationality);
stu.setCampus_id("cam00001");
stu.setCourse_id(null);
stu.setStudent_id(student_id);
em.persist(stu);
return stu;
}
}