/**
     * 获取数据库连接
     * @return 数据库连接
     */
    public static Connection createConn() {
        Connection conn = null;
        try {
            Class.forName(DBData.DRIVER);
            conn = DriverManager.getConnection(DBData.getURLForMySQL(), DBData.USER, DBData.PASSWORD);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
            //JOptionPane.showMessageDialog(Source.getMainWindow(), "创建数据库连接失败,请检查服务器运行状态.");
            //return createConn();
        }
        
        return conn;
    }
    
    /**
     * 获取数据库Statement
     * @param conn 数据库连接
     * @return 数据库stmt
     */
    public static Statement createStmt(Connection conn) {
        Statement stmt = null;
        try {
            stmt = conn.createStatement();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return stmt;
    }
    
    /**
     * 获取数据库PreparedStatement
     * @param conn 连接
     * @param sql sql语句
     * @return PreparedStatement
     */
    public static PreparedStatement prepare(Connection conn, String sql) {
        PreparedStatement ps = null;
        try {
            ps = conn.prepareStatement(sql);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return ps;
    }
    
    /**
     * 关闭Connection
     * @param conn 数据库连接
     */
    public static void close(Connection conn) {
        try {
            conn.close();
            conn = null;
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    
    /**
     * 关闭Statement
     * @param stmt Statement
     */
    public static void close(Statement stmt) {
        try {
            stmt.close();
            stmt.cancel();
            stmt = null;
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    
    /**
     * 关闭PreparedStatement
     * @param pstmt PreparedStatement
     */
    public static void close(PreparedStatement pstmt) {
        try {
            pstmt.close();
            pstmt.cancel();
            pstmt = null;
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    
    /**
     * 关闭结果集
     * @param rs 查询结果集
     */
    public static void close(ResultSet rs) {
        try {
            rs.close();
            rs = null;
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    Connection connection = DB.createConn();
        PreparedStatement pstmt = DB.prepare(connection, sql);//获取stmt
        ResultSet rs = null;
        try {
            pstmt.setString(1, XXXX);
            rs = pstmt.executeQuery();
            
            while(rs.next()){
                XXXXXX
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally{
            DB.close(rs);
            DB.close(pstmt);
            DB.close(connection);
        }