executeQuery（）返回空的ResultSet

Question

I'm creating a simple app which uses JDBC to get data from MySQL. I use a dao to get data from the database. All but one are working fine (code is the same for all DAOs). Also I'm committing INSERT and UPDATE methods manually.

Workbench returns valid result even if I set isolation level read committed manually.

JDBCSessionDao create method:

public void create(Session session) throws SQLException{
        try(PreparedStatement ps = conn.prepareStatement(INSERT_SESSION)){
            conn.setAutoCommit(false);

            LocalTime start = session.getStartTime();
            LocalTime end = session.getEndTime();

            System.out.println(start + ", " + end);
            System.out.println(Time.valueOf(start) + ", " + Time.valueOf(end));

            ps.setTime(1, Time.valueOf(start));
            ps.setTime(2, Time.valueOf(end));
            ps.setDate(3, Date.valueOf(session.getDate()));
            ps.setLong(4, session.getMovieId());

            ps.executeUpdate();

            conn.commit();
            conn.setAutoCommit(true);
        }
        catch (SQLException e){
            logger.error(e.getMessage());
            conn.rollback();
        }
    }

JDBCSessionDao findByDate method

public List<Session> findByDate(LocalDate date) {
    List<Session> sessions = new ArrayList<>();
    SessionMapper mapper = new SessionMapper();

    try(PreparedStatement ps = conn.prepareStatement(SELECT_BY_DATE_ORDER_BY_TIME_ASC)){
        ps.setDate(1, Date.valueOf(date));

        ResultSet rs = ps.executeQuery();

        System.out.println(rs.getFetchSize());

        while(rs.next()){
            Session s = mapper.extractFromResultSet(rs);
            sessions.add(s);
        }
    }
    catch (SQLException e){
        logger.error(e.getMessage());
    }

    return sessions;
}

Query:

String SELECT_BY_DATE_ORDER_BY_TIME_ASC = "SELECT * FROM sessions WHERE session_date=? ORDER by start_time ASC";

JDBCDaoFactory getConnection() method:

private Connection getConnection(){
    String url = "jdbc:mysql://localhost:3306/cinemajee?useLegacyDatetimeCode=false&serverTimezone=Europe/Kiev";
    String user = "root";
    String password = "root";

    try{
        Class.forName("com.mysql.cj.jdbc.Driver");
        return DriverManager.getConnection(url, user, password);
    }
    catch (SQLException | ClassNotFoundException e){
        e.printStackTrace();
        throw new RuntimeException();
    }
}

Query result in workbench: query result

Answer 1

Try modifying the query in your code. Perhaps the session_date parameter isn't working. So change from this:

"SELECT * FROM sessions WHERE session_date=? ORDER by start_time ASC"'

to this:

"SELECT * FROM sessions ORDER by start_time ASC LIMIT 5"'

Answer 2

我忘记了在SessionMapper中更改列名，它们是以驼峰式（例如sessionId）编写的，但是我的数据库列是在蛇形（例如session_id）中编写的。