Java Hibernate打开/关闭会话，DAO的正确方法

我已经编写了这个Hibernate对象DAO，但是通过这种方法，它使用了每次更新会话的方法（我认为这是不对的）

我认为这是不对的，因为我的用户类遇到了问题，其中包含了延迟获取的集合。因为当从DAO检索每个用户时，会话是关闭的。因此，我无法获得我的收藏

由于对象已分离，因此它还不时对表进行大量不必要的更新

有没有办法修复我的DAO，比如使用getCurrentSession（）

HibernateUtil

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);
        }
    }
}

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您可以在HibernateUtil中保存静态会话成员。懒惰初始化。

---

可以随时关闭会话，但在会话未关闭之前，您将继续使用它。

好的方法是将close方法添加到DAO（AbstractDao）中，并将其称为“工作单元”的结束

请不要对会话进行静态引用，会话不是线程安全的

---

---

下面是一个精彩的示例解释：

但这样我将只使用一个会话。这是需要的吗？当您使用startOperation（）获取新会话时，您可以使用closeOperation（）关闭会话，并随时使用。如果将会话设置为静态，则此交互模式不是线程安全的。

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);
        }
    }
}