userloader.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.security;

/**
 * <p>Title: </p>
 * <p>Description: This class is to load a new user through ...</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.ResultSet;

import javax.sql.DataSource;

import com.ebusiness.ebank.servicedelegate.ServiceLocator;
import com.ebusiness.ebank.exception.SystemException;
import com.ebusiness.ebank.util.Constants;

public class UserLoader
{

    private DataSource ds;

    private static UserLoader loader = new UserLoader();

    private UserLoader(){}

    public static UserLoader getInstance() {return loader;}

    //Load UserProfile through data store. It may be a LDAP server
    public UserProfile load(String userID, String[] roles) throws SystemException
    {
        try
        {
            UserPreference pref = getUserPreference(userID);
            return new UserProfile(userID, pref.getLanguage(), roles);
        }
        catch (Exception e)
        {
            throw new SystemException(e);
        }
    }

    private UserPreference getUserPreference(String userID) throws SystemException
    {
        UserPreference pref = null;
        PreparedStatement ps = null;
        Connection con = null;
        try
        {
            if (ds == null )
                ds = ServiceLocator.getInstance().getDataSource(Constants.DATASOURCE_EBANK);
            con = ds.getConnection();
            ps = con.prepareStatement("Select * from Preference where User_ID = ?");
            ps.setString(1, userID);
            ResultSet rs = ps.executeQuery();
            pref = new UserPreference();
            pref.setUserID(userID);
            if (rs.next())
                pref.setLanguage(rs.getString("language"));
            else
                pref.setLanguage("en"); //default to English
        }
        catch (Exception e)
        {
            throw new SystemException(e);
        }
        finally
        {
            try
            {
                if (ps != null)
                   ps.close();
                if (con != null)
                   con.close();
            }
            catch (Exception e)
            {
                throw new SystemException(e);
            }
        }
        return pref;
    }
}