Hibernate中的事务管理与DAO设计模式

时间:2014-11-27 11:51:35

标签: java hibernate design-patterns transactions dao

我有很多表,对于每个表,我们都有DAO接口和DAOImplementation类。

示例DAO接口

public interface CancelPolicyDAO {

public CancelPolicy insertCancelPolicy(CancelPolicy cpdao)throws ChannelDispatcherException;

public CancelPolicy updateCancelPolicy(CancelPolicy cpdao)throws ChannelDispatcherException;

public void deleteCancelPolicy(CancelPolicy cpdao)throws ChannelDispatcherException;

public CancelPolicy findByCancelPolicyData(Integer id, Integer offSetUM, Integer nights, Float pOrAm, Byte isPercent)throws ChannelDispatcherException;

public CancelPolicy findByCancelPolicyId(Integer id)throws ChannelDispatcherException;
}

示例DAOImplementation类

public class CancelPolicyDAOImpl implements CancelPolicyDAO {

@Override
public CancelPolicy insertCancelPolicy(CancelPolicy bean) throws ChannelDispatcherException {

    Session ses = null;
    try {

        ses = HibernateConnector.getInstance().getSession();
        ses.save(bean);
        ses.flush();
        return bean;
    } catch (Exception e) {
        e.printStackTrace();
        throw new ChannelDispatcherException(DbUtil.getStackTraceMessage(e));
    } finally {
        if (ses != null) {
            try {
                ses.close();
            } catch (Exception er) {
                er.printStackTrace();
            }
        }
    }

}

@Override
public CancelPolicy updateCancelPolicy(CancelPolicy bean) throws ChannelDispatcherException {
    Session sess = null;

    try {

        sess = HibernateConnector.getInstance().getSession();
        sess.update(bean);
        sess.flush();
        return bean;
    } catch (Exception e) {
      e.printStackTrace();
        throw new ChannelDispatcherException(DbUtil.getStackTraceMessage(e));
    }

}

@Override
public void deleteCancelPolicy(CancelPolicy bean) throws ChannelDispatcherException {
    Session sess = null;

    try {

        sess = HibernateConnector.getInstance().getSession();
        sess.delete(bean);
        sess.flush();
    } catch (Exception e) {
     e.printStackTrace();
        throw new ChannelDispatcherException(DbUtil.getStackTraceMessage(e));
    }

}

@Override
public CancelPolicy findByCancelPolicyData(Integer id, Integer offSetUM, Integer nights, Float pOrAm, Byte isPercent) throws ChannelDispatcherException {

    Session ses = null;
    try {
        ses = HibernateConnector.getInstance().getSession();
        Query query = ses.createQuery("from CancelPolicy a where "
                + " a.cancelPolicyTypeId =:cancelPolicyTypeId  "
                + " and   a.offsetUnitMultiplier =:offsetUnitMultiplier  "
                + " and   a.nights =:nights  "
                + " and   a.percentOramount =:percentOramount "
                + " and   a.isPercent =:isPercent");

        query.setParameter("cancelPolicyTypeId", id);
        query.setParameter("offsetUnitMultiplier", (offSetUM));
        query.setParameter("nights", (nights));
        query.setParameter("percentOramount", pOrAm);
        query.setParameter("isPercent", isPercent);

        List queryList = query.list();
        if (queryList != null && queryList.isEmpty()) {
            return null;
        } else {
            return (CancelPolicy) queryList.get(0);
        }
    } catch (Exception e) {
       e.printStackTrace();
        throw new ChannelDispatcherException(DbUtil.getStackTraceMessage(e));
    } finally {
        if (ses != null) {
            try {
                ses.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

}

public CancelPolicy findByCancelPolicyId(Integer id) throws ChannelDispatcherException {

    Session ses = null;
    try {
        ses = HibernateConnector.getInstance().getSession();
        Query query = ses.createQuery("from CancelPolicy a where "
                + " a.id =:id  ");

        query.setParameter("id", id);

        List queryList = query.list();
        if (queryList != null && queryList.isEmpty()) {
            return null;
        } else {
            return (CancelPolicy) queryList.get(0);
        }
    } catch ( Exception e) {
       e.printStackTrace();
        throw new ChannelDispatcherException(DbUtil.getStackTraceMessage(e));
    } finally {
        if (ses != null) {
            try {
                ses.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

}  

主要方法示例

 public static void main(String[] args)  {

       // How to handel Transaction in Hibernate ?
     CancelPolicyDAO cancelPolicyDAO = HibernateDAOFactory.getInstance().getCancelPolicyDAO();


     CancelPolicy insertCancelPolicy = cancelPolicyDAO.findByCancelPolicyData(2, 76, 25, 25.36f, 3);
    if(insertCancelPolicy==null){
        CancelPolicy cancelPolicy = new CancelPolicy();
    cancelPolicy.setCancelPolicyTypeId(1);
    cancelPolicy.setNights(2);
     insertCancelPolicy = cancelPolicyDAO.insertCancelPolicy(cancelPolicy);
    }
    Integer autoIncrementId = insertCancelPolicy.getId();

    AvailabilityDAO availabilityDAO =  HibernateDAOFactory.getInstance().getAvailabilityDAO();
    Availability availability = new Availability();
//        using  CancelPolicy autoIncrementId 
    availability.setId(autoIncrementId);
    availability.setCount(2);
    availability.setMaxLos(5);
    availabilityDAO.insertAvailability(availability);
    .
    .
    .
    .
    .


 }

现在我的问题是如何处理DAOImpl中的Transaction?  我应该将Session Object作为每个DAOImpl的参数传递,还是有更好的方法

4 个答案:

答案 0 :(得分:10)

我强烈建议不要重新发明轮子;使用现有的,健壮的和经过测试的代码。

评论已经提到了AOP和Spring框架。这是不可能的。 Spring框架甚至有一个名为Spring Data的子项目,它允许您以声明方式定义查找器方法(如findByCancelPolicyData)。

这将为您节省大量的工作。

如果由于任何原因你不想/不可能使用Spring,你仍然可以阅读基本框架和提到的Spring Data的非常好的文档,以获得关于交易的许多优秀想法(通过AOP ),代码重用(通过通用DAO)或API设计。不要错过这个读物。

答案 1 :(得分:8)

虽然使用Spring可能是添加事务管理的最佳方式,但即使不重新考虑所有代码库,您仍然可以解决它。

您需要做的是设置以下配置:

hibernate.current_session_context_class=thread

您应该通过以下方式访问会话:

[SessionFactory.getCurrentSession()][1];

您仍需要在服务层声明交易边界:

Session sess = factory.openSession();
Transaction tx = null;
try {
    tx = sess.beginTransaction();

    dao1.find();
    dao2.save(entity);

    tx.commit();
}
catch (RuntimeException e) {
    if (tx != null) tx.rollback();
    throw e;
}
finally {
    sess.close();
}

DAO1和DAO2都将使用相同的Hibernate Session和相同的Transaction。

为了避免这种冗长的事务管理代码处理,您可以编写一个简单的TransactionManager实用程序,例如:

public static abstract class TransactionCallable<T> {
    public abstract T execute();
}

public class TransactionManager {   
    public static <T> T doInTransaction(TransactionCallable<T> callable) {
        T result = null;
        Session session = null;
        Transaction txn = null;
        try {
            session = sf.openSession();
            txn = session.beginTransaction();

            result = callable.execute();
            txn.commit();
        } catch (RuntimeException e) {
            if ( txn != null && txn.isActive() ) txn.rollback();
            throw e;
        } finally {
            if (session != null) {
                session.close();
            }
        }
        return result;
    }
}

这就是服务的样子:

TransactionManager.doInTransaction(new TransactionCallable<Void>() {
    @Override
    public Void execute() {
        dao1.find();
        dao2.save(entity);
    }
});

答案 2 :(得分:2)

如果您有 Web应用程序并且您没有在项目中使用spring进行会话管理,我建议使用拦截器来分隔DAO之外的会话处理逻辑。您可以参考下面提到的相同文章。请注意,这种方法存在某些CON,但我们发现它是我们案例中最方便的方法。

Open Session in View Pattern

下面是我们如何在View模式中使用Generics的Open Session的示例,我们可以为您提供类,

   public class CancelPolicyDAOImpl extends GenericDAOImpl<CancelPolicy, Long> implements CancelPolicyDAO {

   @Override
public CancelPolicy insertCancelPolicy(CancelPolicy bean) throws ChannelDispatcherException {


        try {
          // save method is implemented in GenericDAOImpl described below.
           return save(bean);
        } catch (Exception e) {
            e.printStackTrace();
        } 

        }
//remaining methods
}

在上面的代码中使用了在GenericHibernateDAOImpl中实现的save方法,如下所示。您可以使用Google for GenericHibernateDAOImpl类并抓取它,其中包含许多其他基本操作方法。

public abstract class GenericDAOImpl<T, ID extends Serializable>  {

    private Session session;

 public T save(final T entity) {
        Transaction trans = null;
        try {
            trans = session.beginTransaction();
            session.saveOrUpdate(entity);
            session.flush();
            trans.commit();
        } catch (Exception ex) {
            rollBackTransaction(trans);
// you might require to throw error again here
        }
        return entity;
    }

//in case any complex operations required you can get core session object from this method
    protected Session getSession() {
        return sessionFactory.getCurrentSession();
    }
}

现在回到你关于在哪里获得会话的问题,如上所示GenericHibernateDAOImpl会话是通过getCurrentSession方法从singleton sessionFactory中检索的。请注意,您需要在获取当前会话之前运行活动事务,您可以在拦截器中使用该链接(本文开头提供的链接)。

请告诉我。

答案 3 :(得分:0)

不需要使用框架,CancelPolicy对象是主要对象,它应该具有休眠功能(级联)检查链接(Cascading life cycle

所以你用所有必需的关系填充CancelPolicy对象,并说保存,它将保存相关对象的所有图形。