dao.java

我在加拿大学习的一个比较复杂的在线银行程序.

package com.ebusiness.ebank.dao;

/**
 * <p>Title: </p>
 * <p>Description: This is an abstract super class to access data. All of the concrete
 *                  DAO classes needs to extends this super class.</p>
 * <p>Copyright: Copyright (c) 2005</p>
 * <p>Company: eBusiness Inc., All right reserved</p>
 * @author unascribed
 * @version 1.0
 */

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.Statement;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.sql.DataSource;

import org.apache.log4j.Logger;
import org.apache.log4j.MDC;

import com.ebusiness.ebank.servicedelegate.ServiceLocator;
import com.ebusiness.ebank.servicedelegate.ServiceLocatorException;
import com.ebusiness.ebank.exception.SystemException;
import com.ebusiness.ebank.exception.ErrorMessages;
import com.ebusiness.ebank.security.UserProfile;
import com.ebusiness.ebank.util.Constants;

public class DAO
{
    protected Connection con;
    protected PreparedStatement ps;
    protected ResultSet rs;
    protected UserProfile profile;

    private static DataSource ds;

    private Logger log = Logger.getLogger(this.getClass());

    //Set connection to this DAO object
    protected void setConnection() throws SystemException
    {
        try
        {
            if (ds == null)
                ds = ServiceLocator.getInstance().getDataSource(Constants.DATASOURCE_EBANK);
            con = ds.getConnection();
        }
        catch (ServiceLocatorException sle)
        {
            MDC.put(Constants.USER_ID, profile.getUserID());
            log.fatal(ErrorMessages.FAIL_TO_LOOKUP_DATASOURCE + " for " + Constants.DATASOURCE_EBANK, sle);
            throw new SystemException(sle);
        }
        catch (SQLException se)
        {
            MDC.put(Constants.USER_ID, profile.getUserID());
            log.error(ErrorMessages.FAIL_TO_CREATE_DATABASE_CONNECTION, se);
            throw new SystemException(se);
        }
    }

    //Close all of the data resources
    protected void close()
    {
        closeStatement();
        try
        {
            if (con != null)
                con.close();
        }
        catch(SQLException se)
        {
            MDC.put(Constants.USER_ID, profile.getUserID());
            log.error(ErrorMessages.FAIL_TO_CLOSE_DATABASE_CONNECTION, se);
        }
    }

    //Close Statement belonging to this object only
    protected void closeStatement()
    {
        closeStatement(this.ps);
    }

    //Close specified Statement
    protected void closeStatement(Statement s)
    {
        try
        {
            if (s != null)
                s.close();
        }
        catch(Exception se)
        {
            MDC.put(Constants.USER_ID, profile.getUserID());
            log.error(ErrorMessages.FAIL_TO_CLOSE_DATABASE_STATEMENT, se);
        }
    }

    public void setUserProfile(UserProfile profile)
    {
        this.profile = profile;
    }
}