Question

我正在尝试调用存储为会话范围变量的变量。如果我运行第一个if语句，则作用域变量调用有效。当我运行else语句并且只输入名称而没有地址（但是先前输入的名称带有存储的地址）时，不会返回与此名称匹配的地址。任何帮助将不胜感激，因为我有点迷失了。谢谢

@WebServlet("/Test2") // tells server under which URL to offer this servlet 
public class UserRegistration extends HttpServlet {

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

        // set content-type header before accessing the Writer 
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        // then write the response 
        out.println("<html>" + "<head><title>Online Shopping Directory</title></head>");
        //Get the identifier of the book to display 

        out.println("<body bgcolor=\"#ffffff\">"
                + "<h2>Please enter your name:</h2>" + "<form method=\"get\">"
                + "<input type=\"text\" name=\"username\" size=\"25\">"
                + "<p></p>"
                + "<h2>Please enter your address:</h2>" + "<form method=\"get\">"
                + "<input type=\"text\" name=\"useraddress\" size=\"25\">"
                + "<p></p>"
                + "<input type=\"submit\" value=\"Submit\">"
                + "<input type=\"reset\" value=\"Reset\">"
                + "</form>");

        String name = request.getParameter("username");
        String address = request.getParameter("useraddress");
        HttpSession session = request.getSession();
        session.setAttribute("username", address);

        if ((name != null) && (name.length() > 0) && (address != null) && (address.length() > 0)) {

            out.println("The username " + name + " has been saved for "
                    + "this session. The address of this user is "
                    + (String) session.getAttribute("username"));
        } else if ((name == "username") && (address == null)) {
            out.println("The username " + name + " is already saved. The address of this user is " + (String) session.getAttribute("username"));
        }
        out.println("</body></html>");
        out.close();
    }
}

Answer 1

我认为你应该使用equals而不是==

 if ((name.equals("username")) && (address.equals(""))) {
        out.println("The username " + name + " is already saved. The address of this user is " + (String) session.getAttribute("username"));
    }

Java中的范围变量。如何在一个范围内链接两个变量？

1 个答案: