java - SQL 查询没有结果如何在我的程序中告诉用户

Question

我正在构建一个检查用户角色的程序。当一个按钮被按下时，它使用用户 ID 来查询我们数据库的角色/组表。如果一个人不在角色/组表中，那么他们就是请求者。我有以下代码，想知道为什么最后一个 else if 语句不起作用。

当我们将某人设置为请求者时，他们实际上会从角色/组表中删除。所以 resultset 应该是空的。对吧？

ResultSet rs = stmt.executeQuery(getRolesQuery2.toString());
                try
                {
                    boolean empty = true;
                    while (rs.next())
                    {
                        empty = false;
                        userRole = rs.getInt(1);
                        userGroup = rs.getInt(2);
                        System.out.println("The Users Current Role/Group is: " +userRole+ "/" +userGroup);
                        if(userRole == 4 && userGroup == 1)
                        {
                            userRoleLbl.setText("The User Role/Group is: " +userRole+ "/" +userGroup+ " NDS Administrator");
                        }
                        else if(userRole == 1 && userGroup == 3)
                        {
                            userRoleLbl.setText("The User Role/Group is: " +userRole+ "/" +userGroup+ " Privacy Administrator");
                        }
                        else if(userRole == 1 && userGroup == 5)
                        {
                            userRoleLbl.setText("The User Role/Group is: " +userRole+ "/" +userGroup+ " Security Administrator");
                        }
                        else if(userRole == 1 && userGroup == 7)
                        {
                            userRoleLbl.setText("The User Role/Group is: " +userRole+ "/" +userGroup+ " ORD Administrator");
                        }
                        else if(userRole == 1 && userGroup == 9)
                        {
                            userRoleLbl.setText("The User Role/Group is: " +userRole+ "/" +userGroup+ " OEF-OIF Administrator");
                        }
                        else if(userRole == 1 && userGroup == 11)
                        {
                            userRoleLbl.setText("The User Role/Group is: " +userRole+ "/" +userGroup+ " Surgery Administrator");
                        }
                        else if(userRole == 1 && userGroup == 13)
                        {
                            userRoleLbl.setText("The User Role/Group is: " +userRole+ "/" +userGroup+ " Capri Administrator");
                        }
                        else if(userRole == 3 && userGroup == 15)
                        {
                            userRoleLbl.setText("The User Role/Group is: " +userRole+ "/" +userGroup+ " DART Super User");
                        }
                        //TODO: Add some handling for if the role/group is not present which means they are a requester
                        else if(empty)
                        {
                            userRoleLbl.setText("The User is a Requester");
                        }

                    }

Answer 1

因为你有

empty = false;

在你的时间里

你应该在 while 之外检查这个值，这样如果你的结果集是空的，它就是 true

         try
            {
                boolean empty = true;
                while (rs.next())
                {  
                  //your if else
                }

           if(empty)
              {
                userRoleLbl.setText("The User is a Requester");
              }
           }