Question

以下客户端代码从服务器接受“来宾”对象：

protected static void sendLoginRequest(String email, String password) {
    try(
        Socket socket = new Socket("127.0.0.1", 44444);
        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        BufferedWriter out = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
    ){
        out.write("LGNR");
        out.flush();
        out.newLine();
        out.flush();

        out.write(email);
        out.flush();
        out.newLine();
        out.flush();            

        out.write(password);
        out.flush();
        out.newLine();
        out.flush();

        in.ready();
        switch(in.readLine()) {
        case "SU":
            Guest g = null;
            try(ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());){
                g = (Guest) ois.readObject();
            }catch(ClassNotFoundException | IOException e) {
                System.out.println(e.getMessage());
                e.printStackTrace();
            }
            GuestProfileMenu.generateMenu(g);
            break;
        case "WP":
            System.out.println("Invalid Password.");
            break;
        case "IE":
            System.out.println("Email not found.");
            break;
        }

    }catch(IOException e) {
        System.out.println("No response from Server.");
        System.out.println(e.getMessage());
    }
}

在服务器端，它看起来像这样：

private void userLogin(Socket socket, BufferedReader in, BufferedWriter out) {
    System.out.println(socket.getInetAddress().getHostName() + ":" + socket.getLocalPort() + " - has sent a login request.\r\n");

    FileManager.openGuestFile();
    ArrayList<Guest> gList = FileManager.getGuestList();

    try{
        in.ready();
        String email = in.readLine();
        System.out.println(socket.getInetAddress().getHostName() + ":" + socket.getLocalPort() + " - Email received as: " + email);

        in.ready();
        String password = in.readLine();
        System.out.println(socket.getInetAddress().getHostName() + ":" + socket.getLocalPort() + " - Password received as: " + password);

        boolean exists = false;

        for(int i = 0; i < gList.size(); i++) {
            if (email.equals(gList.get(i).getEmail())) {
                exists = true;
                if (password.equals(gList.get(i).getPassword())) {                      
                    out.write("SU");
                    out.flush();
                    out.newLine();
                    out.flush();
                    try(ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());){            
                        oos.writeObject(gList.get(i));
                        oos.flush();
                    }catch(IOException e) {
                        System.out.println(e.getMessage());
                    }
                }else{
                    out.write("WP");
                    out.flush();
                    out.newLine();
                    out.flush();
                }
            }
        }
        if(!exists) {
            out.write("IE");
            out.flush();
            out.newLine();
            out.flush();
        }
        socket.close();
    }catch(IOException e) {
        System.out.println(e.getMessage());
    }

}

从客户端，它在“ g =（Guest）ois.readObject（）;”行返回ClassNotFoundException：

java.lang.ClassNotFoundException: server.Guest
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at java.io.ObjectInputStream.resolveClass(Unknown Source)
at java.io.ObjectInputStream.readNonProxyDesc(Unknown Source)
at java.io.ObjectInputStream.readClassDesc(Unknown Source)
at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source)
at java.io.ObjectInputStream.readObject0(Unknown Source)
at java.io.ObjectInputStream.readObject(Unknown Source)

错误消息显示“ server.Guest”（即（类包）。（对象））的事实，我可以假定服务器的Guest类的实例与客户端的Guest的实例不同类？那么如何正确地通过套接字发送接收对象呢？

谢谢

Answer 1

错误消息显示“ server.Guest”的事实，即（类包）（对象），我可以假设服务器的Guest实例类与客户端的Guest类的实例不同吗？

是的，异常告诉您，涉及到两个单独的类。

那我如何通过套接字正确发送接收对象？

将自己限制在客户端和服务器都知道的类上。有多种方法可以实现此目的，但是几乎所有方法都涉及在连接的两侧部署相同或等效的.class文件。这里的“等效”是指大约“从同一来源使用相同版本的编译器进行编译”。

为什么我使用ObjectInputStream.readObject（）收到ClassNotFoundException？

1 个答案: