package book.chat;
import java.sql.*;

public class DbManager {
	//類成員Connection
	protected static Connection conn;
    //mysql的驅動類，定義為常量
	public static final String CLASS_NAME = "com.mysql.jdbc.Driver";
    //數據庫的連接地址，定義為常量
	public static final String CONNET_STR = "jdbc:mysql://localhost/chat";
    //獲得Connetion
	public static Connection getConnection() {
		try {
			Class.forName(CLASS_NAME);//使用類反射加載該驅動類
			//獲得一個Connection
			conn = DriverManager.getConnection(CONNET_STR, "root", "");
			return conn;//返回該Connection
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
	}
	//傳入查詢數據庫的sql語句，返回ResultSet
	public static ResultSet getResultSet(String sql) {
		boolean bSuccess = true;
		Statement stmt = null;//聲明Statement stmt
		ResultSet rs = null;//聲明ResultSet rs
		Connection con = getConnection();//調用getConnetion()方法獲得一個Connetion
		if (con == null)//如果Connection 為null則返回假
			bSuccess = false;
		if (bSuccess) {
			try {		
				stmt = con.createStatement();//通過Connection創(chuàng)建一個Statemet
				rs = stmt.executeQuery(sql);//執(zhí)行查詢語句，
			} catch (SQLException e) {
				e.printStackTrace();
				bSuccess = false;
			}
		}
		if (bSuccess)//如果執(zhí)行成功，則返回rs
			return rs;
		else
			return null;
	}
	public static int getTotal( String sql) {
		ResultSet rs = getResultSet( sql );
		try {
			rs.last();
			return rs.getRow();
		} catch (SQLException e) {
			e.printStackTrace();
			return 0;
		}finally{
			releaseConnection();
		}
	}
   //傳入執(zhí)行數據更新的語句，返回更新結果，真為成功執(zhí)行
	public static boolean excute(String sql) {
		boolean bSuccess = true;
		Statement stmt = null;//聲明Statement stmt
		Connection con = getConnection();//調用getConnetion()方法獲得一個Connetion
		if (con == null)//如果Connection 為null則返回假
			bSuccess = false;
		if (bSuccess) {
			try {
				stmt = con.createStatement();//通過Connection創(chuàng)建一個Statemet
				bSuccess = stmt.execute(sql);//執(zhí)行更新數據操作
			} catch (SQLException e) {
				e.printStackTrace();
				bSuccess = false;
			}
		}
		return bSuccess;
	}
    //釋放Connection
	public static void releaseConnection() {
		try {
			if (conn != null)//  如果Connetion 不為null則關閉Connection
				conn.close();
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}

}