private static volatile DBManager instance = null;private DBManager(){}public static DBManager getInstance(){if(instance == null){synchronized(DBManager.class){if(instance == null){instance = new DBManager();}}}return instance;}

static {try{ResourceBundle rb = ResourceBundle.getBundle("database");driver = rb.getString("driver").trim();url = rb.getString("url").trim();user = rb.getString("user").trim();password = rb.getString("password").trim();}catch(Exception e){try {throw new DBException("配置文件未找到", e);} catch (Exception ex) {ex.printStackTrace();}}}

    private  Connection getConnection() throws DBException{Connection conn = null;try {Class.forName(driver);} catch (ClassNotFoundException e) {throw new DBException("数据库驱动未找到",e);}try{conn = DriverManager.getConnection(url, user, password);                }catch(SQLException e){throw new DBException("数据库连接出错，请检查URL,用户名，密码是否正确",e);}return conn;}

/*** * @auther lishan* @description 查询* @param sql 查询语句* @param paras 查询参数 对应sql语句中的?* @return 查询结果(ArrayList)方便使用* @throws DBException* @date 2013年12月16日上午9:27:20*/@SuppressWarnings("rawtypes")public ArrayList execQuery(String sql,Object ...paras) throws DBException{//初始化要使用的变量　　　　　　  Connection conn = null;PreparedStatement ps = null;ResultSet rs = null;ResultSetMetaData rsmd = null;ArrayList<HashMap<String,Object>> result = new ArrayList<HashMap<String,Object>>();try{conn = getConnection();  //获取连接ps = conn.prepareStatement(sql); //使用prepareStatment能够增加性能和防止SQL注入for(int i = 0;i < paras.length;i++){ //将参数赋值给?ps.setObject(i+1, paras[i]); //注意这里是i+1不是i,prepareStatment的索引从1开始}rs = ps.executeQuery(); //执行查询rsmd = rs.getMetaData(); //获取元数据用来获得列名int columnCount = rsmd.getColumnCount();//获得列的总数while(rs.next()){   //遍历结果集HashMap<String,Object> row = new HashMap<String,Object>();for(int i = 1; i < columnCount;i++){row.put(rsmd.getColumnName(i), rs.getObject(i));}result.add(row);}}catch(SQLException e){throw new DBException("数据查询出错", e);}finally{ //关闭资源和连接try {if(rsmd != null){rsmd = null;}if(rs != null){rs.close();}if(ps != null){ps.close();}if(conn != null){conn.close();}} catch (SQLException e) {throw new DBException("数据库关闭出错",e);}}return result;}