删除文件中与登出人员匹配的行

Question

我有一个问题，我在这里从一个回答的问题中发现了一段代码。

这是我的代码:

public class LogoutServlet extends HttpServlet
{
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
             throws ServletException, IOException 
             {
                boolean logout = false;
                RequestDispatcher rd = null;
                Cookie[] c = req.getCookies();
                String name;
                for(Cookie cookie: c)
                {
                    if(cookie.getName().equals("cUsername"))
                    {
                        name = cookie.getValue();
                    }
                }

            if(req.getParameter("logout") != null)
            {
                logout = true;
                rd = req.getRequestDispatcher("loginpagina.jsp");
                rd.forward(req, resp);
            }
            if(logout)
            {               
                File inputFile = new File("C://Users/Jacco_000/Desktop/LoggedUser.txt");
                File tempFile = new File("C://Users/Jacco_000/Desktop/tempfile.txt");
                BufferedReader reader = new BufferedReader(new FileReader(inputFile));
                BufferedWriter writer = new BufferedWriter(new FileWriter(tempFile));
                String lineToRemove = "cUsername";
                String currentLine;
                while((currentLine = reader.readLine()) != null)
                {
                    String trimmedLine = currentLine.trim();
                    if(trimmedLine.equals(lineToRemove))
                    {
                    writer.write(currentLine + System.getProperty("line.seperator"));
                    }
                }
                writer.close();
                reader.close();
                tempFile.renameTo(inputFile);

            }
        }   
 }

它的作用是注销一个登录到网站的用户。登录用户保存在一个名为""LoggedUsers.txt""的文件中。我想要的是，当我登出时，正在登出的名称将从文件中删除，而其他已登录的名称也将被删除，因为这就是现在发生的事情。

谢谢!

Answer 1

根据您的条件，您正在重写要注销的用户名，其余部分将被跳过。你只需要改变你的状况:

if(!trimmedLine.equals(lineToRemove))// use !
{
    writer.write(currentLine);
}

编辑:

我希望这是你正在寻找的:

 String name = null;
// to do rest
if(!trimmedLine.equals(name))// use !
{
    writer.write(trimmedLine);
    writer.newLine();// add, if required
}

在你的LoginServlet.java中你没有掉饼干:

if(loginSucces)
{
    Cookie c1 = new Cookie("cUsername", name);
    Cookie c2 = new Cookie("cPassword", pass);
    resp.addCookie(c1);//you are missing this line
    rd = req.getRequestDispatcher("Welkom.jsp");
}

现在唯一的问题是，当我重新登录到用户的用户名在loggedusers文件

中出现双重

问题似乎是在LoginServlet.java中，您有userLijst列表跟踪登录的用户，因为您从未从列表中删除登录的用户，它被写入文件，因为您多次重新登录。如果列表中包含登录的用户，如

，您可以跳过使用列表，或者您可以添加一个检查项

if(name != null && !name.isEmpty() && !userLijst.contains(name) && pass != null && !pass.isEmpty()) {
  // 
 }

注:将密码存储在cookie中是一个坏主意

Answer 2

这是在登录时将用户名写入loggedusers.txt的代码:

公共类LoginServlet扩展HttpServlet｛userLijst = new ArrayList();

protected void doGet(HttpServletRequest req, HttpServletResponse resp)
         throws ServletException, IOException 
        {
            boolean loginSucces = false;
            String name = req.getParameter("username");
            String pass = req.getParameter("password");
            FileWriter fw = new FileWriter(new File("C://Users/Jacco_000/Desktop/LoggedUser.txt"));
            BufferedWriter out = new BufferedWriter(fw);
            if(!name.isEmpty() && name != null &&  !pass.isEmpty() && pass != null)
            {
                File f = new File("C://Users/Jacco_000/Desktop/users.txt");
                if(f.exists() && f.isFile())
                {
                    Scanner sc = new Scanner(f);
                    sc.useDelimiter(",");
                    while(sc.hasNextLine())
                    {
                        String s = sc.nextLine();
                        Scanner sc2 = new Scanner(s);
                        sc2.useDelimiter(",");
                        String nm = sc2.next();
                        String ps = sc2.next();
                        String rnm = sc2.next();
                        String em = sc2.next();
                        String ad = sc2.next();
                        String ld = sc2.next();

                        if(name.contains(nm) && pass.contains(ps))
                        {
                            loginSucces = true;
                            String loggedUsers = nm;
                            userLijst.add(loggedUsers);
                            for(int i = 0; i < userLijst.size(); i++)
                            {
                                out.write(userLijst.get(i));
                                out.newLine();
                            }
                            out.close();
                            fw.close();
                        }
                    }
                }
            }
            else
            {
                loginSucces = false;
            }   
            RequestDispatcher rd = null;
            if(!loginSucces)
            {
                req.setAttribute("msgs", "Gebruikersnaam en/of Wachtwoord is incorrect");
                rd = req.getRequestDispatcher("loginpagina.jsp");
            }

            if(req.getParameter("register") != null)
            {
                rd = req.getRequestDispatcher("registerpagina.jsp");
            }
            if(loginSucces)
            {
                Cookie c1 = new Cookie("cUsername", name);
                Cookie c2 = new Cookie("cPassword", pass);
                rd = req.getRequestDispatcher("Welkom.jsp");
            }
            rd.forward(req, resp);