Question

我正在JSP中开发电影租赁应用程序。在复选框的帮助下选择电影后，当我使用它进行迭代时，它会给我空指针异常。这是Statement.jsp文件的代码，它为租借的电影创建语句...

<%@page language="java" %>
<%@page import="java.sql.*, java.util.*, mrs.*" %>
<html>
<head>
    <title>Movie Rental Application</title>
</head>
<body>
    <%@include file="Connection.jsp" %>

    <% if (session.getAttribute("Name") != null) {
            String[] checkboxes = null;
            String[] days = null;

            checkboxes = request.getParameterValues("c1");
            days = request.getParameterValues("t1");
            int i = 0;
            for (String title : checkboxes) {
                String Name = session.getAttribute("Name").toString();
                int code = 0;
                ResultSet rs = stmt.executeQuery("select Type from Movies where Title = '" + title + "'");
                String Type = rs.toString();
                if (Type.equalsIgnoreCase("REGULAR")) {
                    code = 0;
                }
                if (Type.equalsIgnoreCase("NEW RELEASE")) {
                    code = 1;
                }
                if (Type.equalsIgnoreCase("CHILDREN")) {
                    code = 2;
                }
                mrs.Movie m = new mrs.Movie(title, code);
                int day = Integer.parseInt(days[i]);
                i++;
                mrs.Rental r = new mrs.Rental(m, day);
                mrs.Customer c = new mrs.Customer(Name);
                c.addRental(r);
                stmt.executeQuery("insert into rents values('" + day + "','" + Name + "','" + title + "')");
                String result = c.statement();
                out.println(result);
            }
            stmt.close();
            con.close();
    %>
    <% }%>
</body>
</html>

这是例外......

Answer 1

您没有检查是否选中了复选框。

public Dictionary<string, List<DummyClass>> FilterAndGroupBy(string type, string date, List<string> names)
{
    // Get the collection
    var collection = GetDummyCollection();

    var filter = new BsonDocument
    {
        {"Date", date},
        {"Type", type}
    };

    // Create the filter
    filter.Add("Name", new BsonDocument
    {
        {"$in", new BsonArray(indexNames)}
    });

    // Create the group, this does not work.
    var group = new BsonDocument
    {
        {"_id",
            new BsonDocument {
                {"Name", "$Name"},
                {"Result", new BsonDocument("$push", new BsonArray()) }
            }
        }
    };

    // Query the group with the filter
    var resultslambda = collection.Aggregate().Match(filter).Group(group).ToList();

    return new Dictionary<string, List<DummyClass>>();
}

您可以参考link以查看复选框根据上述条件返回的值。

每个循环的空指针异常

1 个答案: