Unresolved compilation problems

Question

这是测试类
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;import com.hibernate.model.Student;
public class StudentTest { public static void main(String[] args) {
Student s = new Student();
s.setId(1);
s.setAge(1);
s.setName("s1");

Configuration cfg = new Configuration();//16行
SessionFactory sf = cfg.configure().buildSessionFactory();
Session session = sf.openSession();
session.beginTransaction();
session.save(s);
session.getTransaction().commit();
session.close();
sf.close(); }}
这是报错
Exception in thread "main" java.lang.Error: Unresolved compilation problems: 
Configuration cannot be resolved to a type
Configuration cannot be resolved to a type
SessionFactory cannot be resolved to a type
Session cannot be resolved to a type at StudentTest.main(StudentTest.java:16)