Question

我正在从Mysql数据库中检索行并将每行存储为列表中的对象。我将列表传递给请求范围，我试图使用JSTL循环遍历列表并访问对象变量。

以下是我将行检索为对象的方法：

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{

        // get list of objects
        List<Game> gameRatingsThisWeek = getHighestRatedGameThisWeek();
        request.setAttribute("gameRatingsThisWeek", gameRatingsThisWeek);

        RequestDispatcher rd = getServletContext().getRequestDispatcher("/dashboard.jsp");
        rd.forward(request, response);

    private List<Game> getHighestRatedGameThisWeek() {
        List<Game> list = new ArrayList<Game>();
        try(Connection con = ds.getConnection()){
            String query =   "SELECT overallRating, count(*) as Total, g.name"
                            +"FROM gameSurvey gs, game g"
                            +"WHERE g.id = gs.gameID AND"
                            +"date BETWEEN (NOW() - INTERVAL 7 DAY) AND NOW()"
                            +"GROUP by overallRating"
                            +"ORDER by Total desc";
            PreparedStatement ps = con.prepareStatement(query);
            ResultSet rs = ps.executeQuery();
            while(rs.next()){
                Game game = new Game();
                game.setName(rs.getString("name"));
                game.setRating(rs.getInt("overallRating"));
                game.setTotal(rs.getInt("Total"));
                list.add(game);
            }
            ps.close();

        }catch(SQLException e){}
        return list;

    }

}

我知道SQL查询没问题，因为我之前测试过它。

这是Game类：

public class Game {
    private int rating, total;
    private String name;

    // get
    public int getRating(){
        return rating;
    }
    public int getTotal(){
        return total;
    }
    public String getName(){
        return name;
    }

    // set
    public void setRating(int rating){
        this.rating = rating;
    }
    public void setTotal(int total){
        this.total = total;
    }
    public void setName(String name){
        this.name = name;
    }
}

在dashboard.jsp文件中，我尝试遍历列表：

<c:forEach items="${gameRatingsThisWeek}" var="game">
    <c:out value="${game.name}"></c:out>
</c:forEach>

我导航到检索并转发到.jsp页面的servlet。但没有任何内容输出到网页。

Answer 1

您当前的查询在每个字符串文字中都缺少空格。这意味着您的数据库看到以下语句：

SELECT overallRating, count(*) as Total, g.nameFROM gameSurvey gs, game gWHERE g.id = gs.gameID ANDdate BETWEEN (NOW() - INTERVAL 7 DAY) AND NOW()GROUP by overallRatingORDER by Total desc

只需添加空格并再试一次。

        String query =   "SELECT overallRating, count(*) as Total, g.name "
                        +"FROM gameSurvey gs, game g "
                        +"WHERE g.id = gs.gameID AND "
                        +"date BETWEEN (NOW() - INTERVAL 7 DAY) AND NOW() "
                        +"GROUP by overallRating "
                        +"ORDER by Total desc";

无法使用JSTL打印列表对象内容

1 个答案: