import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * @author xl
 *
 */
public class Database
{
    /** method */
//****************************************************
    /**
     *  getConnection()
     * @return Connection
     */
    public static Connection getConnection() throws Exception
    {
        String driver="com.microsoft.jdbc.sqlserver.SQLServerDriver";
        String dbUrl="jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=ATM";
        String dbUser="sa";
        String dbPassword="37360379";
        Connection conn=null;
        try
        {
            Class.forName(driver);
            conn=DriverManager.getConnection(dbUrl,dbUser,dbPassword);
        }
        catch(Exception e)
        {
           e.printStackTrace();
        }
        return conn;
    }
//**********************************************************
    /**
     * closeConnection()
     */
    public static void closeConnection(Connection conn) throws Exception
    {
        if(conn!=null)
        {
            conn.close();
        }
    }
//************************************************************
    /**
     * executeUpdate()
     * @return int
    */
    public static int executeUpdate(String sql) throws Exception
    {
        int count=0;
        Connection conn=null;
        Statement stmt=null;
        try
        {
            conn=getConnection();
            stmt=conn.createStatement();
            count=stmt.executeUpdate(sql);
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
        finally
        {
            closeConnection(conn);
        }
        return count;
    }
//***************************************************************
    /**
     * executeQuery()
     * @return List
    */
    public static List executeQuery(String sql) throws Exception
    {
        List list=new ArrayList();
        Connection conn=null;
        Statement stmt=null;
        ResultSet rs=null;
        try
        {
            conn=getConnection();
            stmt=conn.createStatement();
            rs=stmt.executeQuery(sql);
           
            ResultSetMetaData rsmd=rs.getMetaData();
            while(rs.next())
            {
                Map map=new HashMap();
                for(int i=1;i<=rsmd.getColumnCount();i++)
                {
                    map.put(rsmd.getColumnName(i),rs.getObject(i));
                }
                list.add(map);
            }
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
        finally
        {
            if(rs!=null)
            {
                rs.close();
            }
            closeConnection(conn);
        }
        return list;
    }
   
    /**
     * 从查询结果List中取值,其中i为List中的第i条记录
     * @param list
     * @param column_name
     * @param i
     * @return
     */
    public static String getValues(List list,String column_name,int i)
    {
        try
        {
            return ((Map)list.get(i)).get(column_name).toString();
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
        return "";
    }

    /**
     * 从查询结果List中取值,此函数适合于查询结果只有一条的情况,此为i值为0的特殊情况
     * @param list
     * @param column_name
     * @return
     */
    public static String getValues(List list,String column_name)
    {
        try
        {
            return ((Map)list.get(0)).get(column_name).toString();
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
        return "";
    }

   
}

////1.对于insert, update, delete语句int count = DbWrapper.executeUpdate(sql);
////2.对于selete语句
//java.util.List list = DbWrapper.executeQuery(sql);
////方法一:按名字取值，注意大小写是严格区分的
//for ( int i = 0; i < list.size(); i++ )
//{
// java.util.Map map = (java.util.Map)list.get(i);
// out.println(map.get("column_name").toString());
//}
////方法二：遍历取值
//for ( int i = 0; i < list.size(); i++ )
//{
// java.util.Map map = (java.util.Map)list.get(i);
// for (java.util.Iterator it = map.keySet().iterator(); it.hasNext();)
// {
//     String column_name = it.next().toString());        // 取值时注意null判断
//     out.println(column_name + " = " + map.get(column_name)  == null ? "" : map.get(column_name).toString());
// }
//}