public User get_user_by_id(int id){
		PreparedStatement st = null;
		String sql = "select * from user where uid = " + id;
		try{
			log.debug(sql);
			st = getPreparedStatement(sql);
			ResultSet res = st.executeQuery();
			if(res.next()){
				return new User(res.getInt("uid"), res.getString("username"), 
						res.getString("password"), res.getInt("motion"),
						res.getInt("motoinLevel"), res.getString("signature"),
						res.getInt("sex"), res.getInt("lat"), res.getInt("lon"),
						res.getInt("state"));
			}
		} catch (SQLException e) {
			e.printStackTrace();
			log.error("Exception : get user by id error!!");
			return null;
		}
		
		return null;
	}