Question

我正在使用RMI创建客户端和服务器应用程序，以便我的服务器将自定义GUI发送到客户端应用程序。我的客户端，服务器和rmiregistry在不同的桌面上但在同一台PC上打开。我的客户端似乎无法连接到服务器，并不断给我我不理解的异常。

这是《 Head First Java Book》中的最后一个项目，我收到了一些我不理解的异常。我尝试使用Google搜索解决方案，但找不到任何帮助。我不知道客户端是否无法连接到服务器，因为客户端源代码没有正确地在rmiregistry上查找存根，或者客户端在执行RMI查找时无法访问存根类。另外，我研究了什么是“ NotBoundException”，但我得出的结论是，存根无法连接到远程服务器。

摘要：

每当我运行客户端类时，都会得到一个我不知道为什么导致它们或如何解决它们的异常。
我的服务器类和rmiregistry正常运行。
不知道客户端是否无法连接到服务器，因为客户端源代码未正确在rmiregistry上查找存根，或者客户端在执行RMI查找时无法访问存根类。

这是服务器代码：

import java.rmi.*;
import java.util.*;
import java.rmi.server.*;

public class RemoteServer extends UnicastRemoteObject implements RemoteInterface {
    HashMap servicelist;

    public RemoteServer () throws RemoteException {
       setUpServices ();
    }
//SET UP SERVICES METHOD
    private void setUpServices () { //THIS METHOD PUTS THE DIFFERENT GUI CLASS IN A HASHMAP
       servicelist = new HashMap <String, Service> ();
       servicelist.put ("Dice Rolling Service", new DiceService ());
       servicelist.put("Day of the week service", new DayOfTheWeekService ());
       servicelist.put("Visual Music Service", new MiniMusicService ());
    }
//GET SERVICE LIST METHOD
    public Object [] getServiceList () throws RemoteException { //THIS METHOD IS CALLED WHEN THE CLIENT WANTS TO DISPLAY A LIST OF GUIS IN THE BROWSER
       System.out.println ("in Remote");
       return servicelist.keySet().toArray();
    }
//GET SERVICE METHOD
    public Service getService (Object serviceKey) throws RemoteException { //THIS METHOD IS CALLED AFTER THE USER SELECTS A GUI FROM THE DISPLAYED LIST OF GUIS ON THE BROWSER
       Service theService = (Service) servicelist.get(serviceKey);
       return theService;
    }

    public static void main (String [] args) {
       try {
            Naming.rebind("RemoteServer", new RemoteServer ()); //CREATE THE REMOTE OBJECT THEN BIND IT TO THE RMIREGISTRY
       } catch (Exception ex) {
           ex.printStackTrace ();
       }
        System.out.println("Remote Service is running");
    }
}

这是客户端代码：

import java.awt.*;
import javax.swing.*;
import java.rmi.*;
import java.awt.event.*;

public class Client {

   JPanel mainPanel;
   JComboBox serviceList;
   ServiceServer server;

//BUILDGUI METHOD
   public void buildGUI () {
      JFrame frame = new JFrame ("RMI Browser"); 
      mainPanel = new JPanel ();
      frame.getContentPane().add(BorderLayout.CENTER, mainPanel);

      Object [] services = getServicesList();

      serviceList = new JComboBox (services); //ADD THE GUIS TO THE JCOMBOBOX (WHICH IS THE DISPLAYABLE LIST)

      frame.getContentPane().add(BorderLayout.NORTH, serviceList);

      serviceList.addActionListener (new MyListListener ());

      frame.setSize (500, 500);
      frame.setVisible (true);
   }

//LOADSERVICE METHOD
   void loadService (Object serviceSelection) { //THIS METHOD ADDS THE SELECTED GUI TO THE BROWSER
       try {
          Service svc = server.getService(serviceSelection);

          mainPanel.removeAll();
          mainPanel.add(svc.getGuiPanel ());
          mainPanel.validate ();
          mainPanel.repaint ();
       } catch (Exception ex) {
          ex.printStackTrace ();
       }
   }

//GETSERVICESLIST METHOD
    Object [] getServicesList () { //THIS METHOD DOES THE RMI LOOKUP, GETS THE STUB AND CALLS THE GETSERVICELIST ()
       Object obj = null;
       Object [] services = null;

       try {
          obj = Naming.lookup("rmi://127.0.0.1/RemoteInterface"); //DOES THE RMI LOOKUP AND GETS THE STUB
       }
       catch (Exception ex) {
        ex.printStackTrace();
       }
       server = (RemoteInterface) obj; //CAST THE STUB TO THE REMOTE INTERFACE SO THAT WE CAN CALL GETSERVICELIST ()

       try {
         service = server.getServiceList(); //THIS GIVES US THE ARRAY OF OBJECTS (WHICH ARE THE GUIS) THAT WILL BE DISPLAYED IN THE JCOMBOBOX FOR THE USER TO SELECT FROM
       } catch (Exception ex) {
          ex.printStackTrace();
       }
       return service;
    }

//MYLISTLISTENER INNER CLASS
    class MyListListener implements ActionListener {
       public void actionPerformed (ActionEvent ev) {
           Object selection = serviceList.getSelectedItem();
           loadService(selection); //AFTER THE USER HAS MADE A SELECTION FROM THE JCOMBOBOX, TAKE THE SELECTION THEY MADE & LOAD THE APPROPIATE GUI
       }
    }

//MAIN METHOD  
    public static void main (String [] args) {
       new Client().buildGUI();
    }
}

这是RemoteInterface界面：

import java.rmi.*;

public interface RemoteInterface extends Remote { //THIS INTERFACE DEFINES TWO METHODS THAT THE REMOTE SERVER WILL IMPLEMENT
    Object [] getServiceList () throws RemoteException;
    Service getService (Object serviceKey) throws RemoteException;
}

这些是我运行客户端类时遇到的异常：

java.rmi.NotBoundException: serviceServer
        at sun.rmi.registry.RegistryImpl.lookup(RegistryImpl.java:227)
        at sun.rmi.registry.RegistryImpl_Skel.dispatch(RegistryImpl_Skel.java:115)
        at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:468)
        at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:300)
        at sun.rmi.transport.Transport$1.run(Transport.java:200)
        at sun.rmi.transport.Transport$1.run(Transport.java:197)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
        at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:573)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:834)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(TCPTransport.java:688)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:687)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
        at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Unknown Source)
        at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source)
        at sun.rmi.server.UnicastRef.invoke(Unknown Source)
        at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
        at java.rmi.Naming.lookup(Unknown Source)
        at ServiceBrowser.getServicesList(ServiceBrowser.java:46)
        at ServiceBrowser.buildGUI(ServiceBrowser.java:16)
        at ServiceBrowser.main(ServiceBrowser.java:69)
java.lang.NullPointerException
        at ServiceBrowser.getServicesList(ServiceBrowser.java:54)
        at ServiceBrowser.buildGUI(ServiceBrowser.java:16)
        at ServiceBrowser.main(ServiceBrowser.java:69)
Exception in thread "main" java.lang.NullPointerException
        at javax.swing.DefaultComboBoxModel.<init>(Unknown Source)
        at javax.swing.JComboBox.<init>(Unknown Source)
        at ServiceBrowser.buildGUI(ServiceBrowser.java:18)
        at ServiceBrowser.main(ServiceBrowser.java:69)

在此问题上待了几天，我真的很乐意提供任何帮助。感谢您抽出宝贵的时间阅读本文。

运行客户端类时如何解决这些异常？（RMI）

0 个答案:

运行客户端类时如何解决这些异常？ （RMI）

0 个答案:

运行客户端类时如何解决这些异常？（RMI）