java - Hibernate 打开/关闭 session ，DAO 的正确方法

Question

我已经编写了这个 Hibernate 对象 DAO，但是使用这种方法时，它使用每次更新方法的 session (我认为这是不正确的)。

我认为它不对的原因是我的 User 类遇到了问题，该类包含延迟获取的集合。因为从 DAO 中检索每个用户时， session 已关闭。因此我无法获得我的 Collection 。

有时，它还会对表进行大量不必要的更新，因为对象已分离。

那么有什么方法可以修复我的 DAO，比如使用 getCurrentSession()？

import java.util.List;

import org.hibernate.HibernateException;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;

import org.test.util.DataAccessLayerException;
import org.test.util.HibernateUtil;

public abstract class AbstractDao {
    protected Session session;
    protected Transaction tx;
    public AbstractDao() {
        HibernateUtil.buildIfNeeded();
    }
    protected void saveOrUpdate(Object obj) {
        try {
            startOperation();
            session.saveOrUpdate(obj);
            tx.commit();
        } catch (HibernateException e) {
            handleException(e);
        } finally {
            HibernateUtil.close(session);
        }
    }
    protected void delete(Object obj) {
        try {
            startOperation();
            session.delete(obj);
            tx.commit();
        } catch (HibernateException e) {
            handleException(e);
        } finally {
            HibernateUtil.close(session);
        }
    }
    protected Object find(Class clazz, Long id) {
        Object obj = null;
        try {
            startOperation();
            obj = session.load(clazz, id);
            tx.commit();
        } catch (HibernateException e) {
            handleException(e);
        } finally {
            HibernateUtil.close(session);
        }
        return obj;
    }
    protected List findAll(Class clazz) {
        List objects = null;
        try {
            startOperation();
            Query query = session.createQuery("from " + clazz.getName());
            objects = query.list();
            tx.commit();
        } catch (HibernateException e) {
            handleException(e);
        } finally {
            HibernateUtil.close(session);
        }
        return objects;
    }
    protected void handleException(HibernateException e) throws DataAccessLayerException {
        HibernateUtil.rollback(tx);
        throw new DataAccessLayerException(e);
    }
    protected void startOperation() throws HibernateException {
        session = HibernateUtil.openSession();
        tx = session.beginTransaction();
    }
}

hibernate 工具

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {

    private static Log log = LogFactory.getLog(HibernateUtil.class);
    private static SessionFactory sessionFactory;

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

    public static SessionFactory buildIfNeeded()
            throws DataAccessLayerException {
        if (sessionFactory != null) {
            return sessionFactory;
        }
        try {
            return configureSessionFactory();
        } catch (HibernateException e) {
            throw new DataAccessLayerException(e);
        }
    }

    public static SessionFactory buildSessionFactory()
            throws HibernateException {
        if (sessionFactory != null) {
            closeFactory();
        }
        return configureSessionFactory();
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }

    public static Session openSession() throws HibernateException {
        buildIfNeeded();
        return sessionFactory.openSession();
    }

    public static void closeFactory() {
        if (sessionFactory != null) {
            try {
                sessionFactory.close();
            } catch (HibernateException ignored) {
                log.error("Couldn't close SessionFactory", ignored);
            }
        }
    }

    public static void close(Session session) {
        if (session != null) {
            try {
                session.close();
            } catch (HibernateException ignored) {
                log.error("Couldn't close Session", ignored);
            }
        }
    }

    public static void rollback(Transaction tx) {
        try {
            if (tx != null) {
                tx.rollback();
            }
        } catch (HibernateException ignored) {
            log.error("Couldn't rollback Transaction", ignored);
        }
    }
}

Answer 1

好的方法是将 close 方法添加到您的 DAO(AbstractDao) 并将其称为“工作单元”的结尾。

而且，请不要对 session 进行静态引用， session 不是线程安全的

---

这里有一个很好的示例解释:Link