实现一个带有重复日程功能的 JavaWeb 日历

下面是一个简单的 JavaWeb 日历的实现，包含了重复日程功能：

首先需要创建一个数据库表来存储日程信息：

CREATE TABLE `calendar` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `title` varchar(255) NOT NULL,
  `description` text NOT NULL,
  `start_time` datetime NOT NULL,
  `end_time` datetime NOT NULL,
  `repeat_type` varchar(50) DEFAULT NULL,
  `repeat_end_time` datetime DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

然后可以创建一个 JavaBean 来表示一个日程：

public class Event {
    private int id;
    private String title;
    private String description;
    private Date startTime;
    private Date endTime;
    private RepeatType repeatType;
    private Date repeatEndTime;

    // getters and setters
}

public enum RepeatType {
    NONE, DAILY, WEEKLY, MONTHLY, YEARLY
}

接下来创建一个 DAO 类来操作数据库：

public class EventDAO {
    private Connection conn;

    public EventDAO(Connection conn) {
        this.conn = conn;
    }

    public List<Event> getEvents(Date startDate, Date endDate) throws SQLException {
        List<Event> events = new ArrayList<>();
        PreparedStatement stmt = conn.prepareStatement("SELECT * FROM calendar WHERE start_time >= ? AND end_time <= ?");
        stmt.setTimestamp(1, new Timestamp(startDate.getTime()));
        stmt.setTimestamp(2, new Timestamp(endDate.getTime()));
        ResultSet rs = stmt.executeQuery();
        while (rs.next()) {
            Event event = new Event();
            event.setId(rs.getInt("id"));
            event.setTitle(rs.getString("title"));
            event.setDescription(rs.getString("description"));
            event.setStartTime(rs.getTimestamp("start_time"));
            event.setEndTime(rs.getTimestamp("end_time"));
            event.setRepeatType(RepeatType.valueOf(rs.getString("repeat_type")));
            event.setRepeatEndTime(rs.getTimestamp("repeat_end_time"));
            events.add(event);
        }
        rs.close();
        stmt.close();
        return events;
    }

    public void addEvent(Event event) throws SQLException {
        PreparedStatement stmt = conn.prepareStatement("INSERT INTO calendar (title, description, start_time, end_time, repeat_type, repeat_end_time) VALUES (?, ?, ?, ?, ?, ?)");
        stmt.setString(1, event.getTitle());
        stmt.setString(2, event.getDescription());
        stmt.setTimestamp(3, new Timestamp(event.getStartTime().getTime()));
        stmt.setTimestamp(4, new Timestamp(event.getEndTime().getTime()));
        stmt.setString(5, event.getRepeatType().name());
        if (event.getRepeatEndTime() == null) {
            stmt.setNull(6, Types.TIMESTAMP);
        } else {
            stmt.setTimestamp(6, new Timestamp(event.getRepeatEndTime().getTime()));
        }
        stmt.executeUpdate();
        stmt.close();
    }

    public void updateEvent(Event event) throws SQLException {
        PreparedStatement stmt = conn.prepareStatement("UPDATE calendar SET title = ?, description = ?, start_time = ?, end_time = ?, repeat_type = ?, repeat_end_time = ? WHERE id = ?");
        stmt.setString(1, event.getTitle());
        stmt.setString(2, event.getDescription());
        stmt.setTimestamp(3, new Timestamp(event.getStartTime().getTime()));
        stmt.setTimestamp(4, new Timestamp(event.getEndTime().getTime()));
        stmt.setString(5, event.getRepeatType().name());
        if (event.getRepeatEndTime() == null) {
            stmt.setNull(6, Types.TIMESTAMP);
        } else {
            stmt.setTimestamp(6, new Timestamp(event.getRepeatEndTime().getTime()));
        }
        stmt.setInt(7, event.getId());
        stmt.executeUpdate();
        stmt.close();
    }

    public void deleteEvent(int id) throws SQLException {
        PreparedStatement stmt = conn.prepareStatement("DELETE FROM calendar WHERE id = ?");
        stmt.setInt(1, id);
        stmt.executeUpdate();
        stmt.close();
    }
}

最后创建一个 Servlet 来处理请求：

public class CalendarServlet extends HttpServlet {
    private EventDAO eventDAO;

    public void init() throws ServletException {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/calendar?useUnicode=true&characterEncoding=utf-8", "root", "123456");
            eventDAO = new EventDAO(conn);
        } catch (ClassNotFoundException | SQLException e) {
            throw new ServletException(e);
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String action = request.getParameter("action");
        if ("list".equals(action)) {
            listEvents(request, response);
        } else if ("form".equals(action)) {
            showEventForm(request, response);
        } else if ("delete".equals(action)) {
            deleteEvent(request, response);
        } else {
            response.sendError(HttpServletResponse.SC_BAD_REQUEST);
        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String action = request.getParameter("action");
        if ("add".equals(action)) {
            addEvent(request, response);
        } else if ("update".equals(action)) {
            updateEvent(request, response);
        } else {
            response.sendError(HttpServletResponse.SC_BAD_REQUEST);
        }
    }

    private void listEvents(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String startDateString = request.getParameter("start");
        String endDateString = request.getParameter("end");
        DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
        try {
            Date startDate = dateFormat.parse(startDateString);
            Date endDate = dateFormat.parse(endDateString);
            List<Event> events = eventDAO.getEvents(startDate, endDate);
            request.setAttribute("events", events);
            request.getRequestDispatcher("/WEB-INF/views/calendar.jsp").forward(request, response);
        } catch (ParseException | SQLException e) {
            throw new ServletException(e);
        }
    }

    private void showEventForm(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String idString = request.getParameter("id");
        Event event = new Event();
        if (idString != null) {
            try {
                int id = Integer.parseInt(idString);
                event = eventDAO.getEvent(id);
            } catch (NumberFormatException | SQLException e) {
                throw new ServletException(e);
            }
        }
        request.setAttribute("event", event);
        request.getRequestDispatcher("/WEB-INF/views/eventForm.jsp").forward(request, response);
    }

    private void addEvent(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Event event = getEventFromRequest(request);
        try {
            eventDAO.addEvent(event);
        } catch (SQLException e) {
            throw new ServletException(e);
        }
        response.sendRedirect(request.getContextPath() + "/calendar?action=list");
    }

    private void updateEvent(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Event event = getEventFromRequest(request);
        try {
            eventDAO.updateEvent(event);
        } catch (SQLException e) {
            throw new ServletException(e);
        }
        response.sendRedirect(request.getContextPath() + "/calendar?action=list");
    }

    private void deleteEvent(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String idString = request.getParameter("id");
        if (idString != null) {
            try {
                int id = Integer.parseInt(idString);
                eventDAO.deleteEvent(id);
            } catch (NumberFormatException | SQLException e) {
                throw new ServletException(e);
            }
        }
        response.sendRedirect(request.getContextPath() + "/calendar?action=list");
    }

    private Event getEventFromRequest(HttpServletRequest request) throws ServletException, IOException {
        String idString = request.getParameter("id");
        String title = request.getParameter("title");
        String description = request.getParameter("description");
        String startString = request.getParameter("start");
        String endString = request.getParameter("end");
        String repeatTypeString = request.getParameter("repeat_type");
        String repeatEndString = request.getParameter("repeat_end");
        DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Event event = new Event();
        if (idString != null) {
            try {
                int id = Integer.parseInt(idString);
                event.setId(id);
            } catch (NumberFormatException e) {
                throw new ServletException(e);
            }
        }
        event.setTitle(title);
        event.setDescription(description);
        try {
            Date start = dateFormat.parse(startString);
            event.setStartTime(start);
        } catch (ParseException e) {
            throw new ServletException(e);
        }
        try {
            Date end = dateFormat.parse(endString);
            event.setEndTime(end);
        } catch (ParseException e) {
            throw new ServletException(e);
        }
        if (repeatTypeString != null) {
            RepeatType repeatType = RepeatType.valueOf(repeatTypeString.toUpperCase());
            event.setRepeatType(repeatType);
        }
        if (repeatEndString != null && !repeatEndString.isEmpty()) {
            try {
                Date repeatEnd = dateFormat.parse(repeatEndString);
                event.setRepeatEndTime(repeatEnd);
            } catch (ParseException e) {
                throw new ServletException(e);
            }
        }
        return event;
    }
}

最后在 web.xml 中配置 Servlet 映射：

<servlet>
    <servlet-name>calendarServlet</servlet-name>
    <servlet-class>com.example.calendar.CalendarServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>calendarServlet</servlet-name>
    <url-pattern>/calendar</url-pattern>
</servlet-mapping>

这样就完成了一个简单的带有重复日程功能的 JavaWeb 日历。