hibernatemessagemanager.java

该留言板使用JSP/servlet+hibernate+MySQL制作而成！详细内容内容请看JAVADOC说明文档．

/*
 * HibernateMessageManager.java
 *
 * Created on 2007年5月28日, 下午7:59
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */

/**
 *
 * @author abc
 */
package message_board;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;
import java.util.Properties;

import net.sf.hibernate.HibernateException;
import net.sf.hibernate.MappingException;
import net.sf.hibernate.Query;
import net.sf.hibernate.Session;
import net.sf.hibernate.SessionFactory;
import net.sf.hibernate.Transaction;
import net.sf.hibernate.cfg.Configuration;

public class HibernateMessageManager implements BoardManager
{

    private Connection          _connection;
    private SessionFactory      _sessionFactory;
    private Session             _currentSession;

    public HibernateMessageManager(Connection connection)
    {
        _connection = connection;

        Configuration configuration = new Configuration();
        try
        {
           
            configuration.addClass(Message.class);
       
        }
        catch (MappingException mappingFailure)
        {
            throw new IllegalArgumentException(
                    "Cannot find required object classes, check CLASSPATH : " + mappingFailure);
        }
        Properties props = new Properties();
        props.put("hibernate.dialect", "net.sf.hibernate.dialect.MySQLDialect");
        props.put("hibernate.statement_cache.size", "0");
        configuration.setProperties(props);

        try
        {
            _sessionFactory = configuration.buildSessionFactory();
        }
        catch (HibernateException sessionFailure)
        {
            throw new IllegalArgumentException(
                    "Cannot build session factory, check configuration : " + sessionFailure);
        }
    }

    /*-- getting objects --*/

    public List getMessages() throws DataException
    {
        return getAllItems("from Message as message order by message.id asc");
    }

    private List getAllItems(String query) throws DataException
    {
        initSession();
        List list = null;
        try
        {
            Query allTeams = _currentSession.createQuery(query);
            list = allTeams.list();
        }
        catch (HibernateException unexpected)
        {
            throw new DataException(unexpected.getMessage());
        }
        finally
        {
            flushSession();
        }
        return list;
    }


    /*-- adding and modifying objects --*/

    public boolean addNewMessage(Message message) throws DataException
    {
        return addOrModifyObject(message, "ADD");
    }
    public boolean modifyMessage(Message message) throws DataException
    {
        return addOrModifyObject(message, "MODIFY");
    }


    private boolean addOrModifyObject(Message message, String action) throws DataException
    {
        initSession();
        Transaction tx = null;
        try
        {
            tx = _currentSession.beginTransaction();
            _currentSession.saveOrUpdate(message);
            tx.commit();
        }
        catch (HibernateException cannotSaveOrUpdate)
        {
            try
            {
                tx.rollback();
            }
            catch (HibernateException cannotRollback)
            {
                // log this error
            }
            throw new DataException("Unable to " + action + " : " + cannotSaveOrUpdate.getMessage());
        }
        finally
        {
            flushSession();
        }

        return false;
    }
  /*-- delete objects --*/

    public boolean deleteMessage(int id) throws DataException
    {
        initSession();
        Transaction tx = null;
        try
        {
            tx = _currentSession.beginTransaction();
            Message deleted = (Message)loadObjectById(Message.class,id);
           _currentSession.delete(deleted);
            tx.commit();
        }
        catch (HibernateException cannotDelete)
        {
            try
            {
                tx.rollback();
            }
            catch (HibernateException cannotRollback)
            {
                // log this error
            }
            throw new DataException("Unable to delete  : " + cannotDelete.getMessage());
        }
        finally
        {
            flushSession();
        }
        return false;
    }
    
    /*-- utility methods --*/
    private Object loadObjectById(Class clazz, int id) throws DataException
    {
        initSession();
        Object rv = null;
        try
        {
            rv = _currentSession.load(clazz, new Integer(id));
        }
        catch (HibernateException unexpected)
        {
            throw new DataException(unexpected.getMessage());
        }
        finally
        {
            flushSession();
        }
        return rv;
    }
    private void initSession()
    {
        if (_currentSession == null)
        {
            _currentSession = _sessionFactory.openSession(_connection);
        }
    }

    private void flushSession()
    {
        try
        {
            if (_currentSession != null)
            {
                _currentSession.flush();
            }
        }
        catch (HibernateException sessionFlushFailure)
        {
            // log this error
        }
    }

    public void releaseResources()
    {
        if (_connection != null)
        {
            try
            {
                if (_currentSession != null)
                {
                    _currentSession.connection().close();
                    _currentSession.close();
                    _currentSession = null;
                }
                _connection.close();

            }
            catch (HibernateException sessionCloseFailure)
            {
                // log this error
            }
            catch (SQLException connectionCloseFailure)
            {
                // log this error
            }
        }
    }


}