Question

我开始使用Hibernate并遵循javabrains的教程。但buildsessionfactory似乎已被弃用。我搜索并找到了solution。

但是，当我尝试从数据库中获取对象时，我在最后一行的sysout处得到NullPointerException，并且甚至没有条目保存到数据库中。但是，如果我注释掉对象检索部分，它可以正常工作并保存到数据库中。

我做错了什么？

    public class HibernateTest {
        private static SessionFactory sessionFactory;
        private static ServiceRegistry serviceRegistry;

        private static SessionFactory configureSessionFactory() throws HibernateException {
        Configuration configuration = new Configuration();
        configuration.configure();
        serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry();        
        sessionFactory = configuration.buildSessionFactory(serviceRegistry);
        return sessionFactory;
        }

        public static void main(String[] args) {
        UserDetails user = new UserDetails();
        user.setUserId(1);
        user.setUserName("User's name");
        user.setAddress("Chingeltei");
        user.setJoinedDate(new Date());
        user.setDescription("Description of the user");

        Session session = configureSessionFactory().openSession();
        session.beginTransaction();
        session.save(user);
        session.getTransaction().commit();
        session.close();

  //    user = null;
  //    session = configureSessionFactory().openSession();
  //    session.beginTransaction();
  //    user = (UserDetails) session.get(UserDetails.class, 1);

  //    System.out.println("User name retreived is: "+user.getUserName());

        }

    }

UserDetails.java

import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.persistence.Transient;

@Entity 
@Table (name="user_details")
public class UserDetails {

    @Id
    @Column (name="userid")
    private int userId;
    @Column (name="username")
    private String userName;
    @Temporal (TemporalType.DATE)
    private Date joinedDate;
    private String address;
    @Transient
    private String description;

    public int getUserId() {
        return userId;
    }
    public String getUserName() {
        return userName;
    }
    public Date getJoinedDate() {
        return joinedDate;
    }
    public String getAddress() {
        return address;
    }
    public String getDescription() {
    return description;
    }
    public void setUserId(int aUserId) {
        userId = aUserId;
    }
    public void setUserName(String aUserName) {
        userName = aUserName;
    }
    public void setJoinedDate(Date aJoinedDate) {
        joinedDate = aJoinedDate;
    }
    public void setAddress(String aAddress) {
        address = aAddress;
    }
    public void setDescription(String aDescription) {
        description = aDescription;
    }
}

Answer 1

正如教程所述，您应该为每个应用程序创建一次sessionFactory。因此，您应该使用已存在的configureSessionFactory()引用，而不是第二次调用sessionFactory。

从休眠中检索对象

1 个答案: