JAVA：RMI回调->对象已导出 [英] JAVA: RMI Callback -> object already exported

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问题描述

这是我的第一个问题，对不起，如果我把它设为我的英语不对。

this is my first question, so sorry if i'll make it incorrect and for my english.

我必须用Java做一个分布式-子手项目，有客人，球员和大师（更多比赛）。当用户（已经注册）登录自己或主服务器打开比赛时，服务器必须将所有事件通知给所有访客（仅访客）。
在客户端中，我必须创建2个存根，其中1个用于服务器，另一个用于图形界面（swing）。

I have to do a distributed-hangman project in java, there are guests, players and masters (more matches). When a user(already registered) log himself or when a master open a match, the server must notifies to all guests (only guests) the event. In the client i had to create 2 stub, 1 for the server, the other one for the graphic interface (swing).

线程池用于管理比赛，现在不使用。
这是客户端代码：

The threadpool is for manage the matches, not used now. This is the client code:

package User;

public class Utente extends RemoteServer implements UserInterface, GraphicInterface,Serializable {

private static final long serialVersionUID = 2L;
private String name;
private String password;
private String host = "localhost";
private Socket soc;
private int port = 1800;
private UserInterface stub = null;
private RegistryInterface server_interface = null;
private Registry server_registry;


public Utente(){
    super();
    this.name = "user";
    this.password = "passwd";
    //per connettersi al server
    try {
        server_registry = LocateRegistry.getRegistry(host);
        server_interface = (RegistryInterface)server_registry.lookup("HANGMAN-SERVER");
    } catch (RemoteException | NotBoundException e) {
        System.out.println("errore connessione lato client");
        e.printStackTrace();
    }
    //per l' rmi con la gui

}


public synchronized boolean login(String n, String p) throws RemoteException {
    boolean esito = false;
    export();
    esito = server_interface.login(n,p,stub);
    return esito;
}

public synchronized boolean logout() throws RemoteException {
    boolean esito = false;
    esito = server_interface.logout(name,stub);
    return esito;
}

public synchronized void notifyMatch(ArrayList<Partita> lista_partite) throws RemoteException {
    if(lista_partite!=null){
        if(lista_partite.size()==0){
            System.out.println("Ancora nessuna partita aperta.");
        }
        else{
            for(int i = 0;i<lista_partite.size();i++){
            System.out.println(lista_partite.get(i).getNameMatch());
            }
        }
    }
}

public void connect(){
    try {
        soc = new Socket(host, port);
    } catch (UnknownHostException e1) {
        e1.printStackTrace();
    } catch (IOException e1) {
        e1.printStackTrace();
    }

}


public static void main(String[] args) {
    Utente user = new Utente();
    Registry c;
    GraphicInterface stubExport = null;
    try{
        stubExport = (GraphicInterface)UnicastRemoteObject.exportObject(user,3900);
        LocateRegistry.createRegistry(5000);
        c=LocateRegistry.getRegistry();
        c.rebind("GraphicUI", stubExport);
    }
    catch (RemoteException e) {
        System.out.println("errore nel client: " + e.toString());
    }
    MainPanel startPanel = new MainPanel();
    startPanel.setVisible(true);    
}



}

错误列表：

UI export problems
java.rmi.server.ExportException: object already exported
    at sun.rmi.transport.ObjectTable.putTarget(Unknown Source)
    at sun.rmi.transport.Transport.exportObject(Unknown Source)
    at sun.rmi.transport.tcp.TCPTransport.exportObject(Unknown Source)
    at sun.rmi.transport.tcp.TCPEndpoint.exportObject(Unknown Source)
    at sun.rmi.transport.LiveRef.exportObject(Unknown Source)
    at sun.rmi.server.UnicastServerRef.exportObject(Unknown Source)
    at java.rmi.server.UnicastRemoteObject.exportObject(Unknown Source)
    at java.rmi.server.UnicastRemoteObject.exportObject(Unknown Source)
    at User.Utente.export(Utente.java:59)
    at User.Utente.login(Utente.java:100)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at sun.rmi.server.UnicastServerRef.dispatch(Unknown Source)
    at sun.rmi.transport.Transport$1.run(Unknown Source)
    at sun.rmi.transport.Transport$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.Transport.serviceCall(Unknown Source)
    at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(Unknown Source)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$254(Unknown Source)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$$Lambda$1/1989325584.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at registry.Server.callbackClient(Server.java:189)
    at registry.Server.login(Server.java:201)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at sun.rmi.server.UnicastServerRef.dispatch(Unknown Source)
    at sun.rmi.transport.Transport$1.run(Unknown Source)
    at sun.rmi.transport.Transport$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.Transport.serviceCall(Unknown Source)
    at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(Unknown Source)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$254(Unknown Source)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$$Lambda$1/1786588690.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
    at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Unknown Source)
    at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source)
    at sun.rmi.server.UnicastRef.invoke(Unknown Source)
    at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(Unknown Source)
    at java.rmi.server.RemoteObjectInvocationHandler.invoke(Unknown Source)
    at com.sun.proxy.$Proxy0.login(Unknown Source)
    at User.Utente.login(Utente.java:101)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at sun.rmi.server.UnicastServerRef.dispatch(Unknown Source)
    at sun.rmi.transport.Transport$1.run(Unknown Source)
    at sun.rmi.transport.Transport$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.Transport.serviceCall(Unknown Source)
    at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(Unknown Source)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$254(Unknown Source)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$$Lambda$1/1989325584.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
    at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Unknown Source)
    at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source)
    at sun.rmi.server.UnicastRef.invoke(Unknown Source)
    at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(Unknown Source)
    at java.rmi.server.RemoteObjectInvocationHandler.invoke(Unknown Source)
    at com.sun.proxy.$Proxy1.login(Unknown Source)
    at gui.MainPanel$2.actionPerformed(MainPanel.java:110)
    at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
    at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
    at java.awt.Component.processMouseEvent(Unknown Source)
    at javax.swing.JComponent.processMouseEvent(Unknown Source)
    at java.awt.Component.processEvent(Unknown Source)
    at java.awt.Container.processEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Window.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$500(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

感谢您的耐心等待，我希望这个问题能够顺利解决。我知道代码很丑陋，时间不多，我也做了很多更改。

Thank you for your patience, i hope the question is well formed. The code is ugly i know, not much time and i changed it a lot.

推荐答案

可能，我想我已经找到了您的 Utente 类中发生错误。您已在代码中的2个位置导出了对象，这导致 java.rmi.server.ExportException：对象已导出。

Probably, I guess I have found the error in your Utente class. You have exported your object at 2 places in your code, which results in java.rmi.server.ExportException:object already exported.

在Utente的main（）方法中，您有

In your Utente's main() method, you have 

stubExport = (GraphicInterface)UnicastRemoteObject.exportObject(user,3900);

其中 用户 是Utente类的对象。

where user is an object of class Utente.

此外，在同一类的login（）方法中，您正在调用export（）方法，该方法包含：-

Also, in the same class' login() method, you are calling export() method, which contains :-

stub = (UserInterface) UnicastRemoteObject.exportObject(this,0);

这里，这与Utente当前有关调用对象，在这种情况下，将是 user 用户，该对象早已导出。

Here, this would pertain to Utente's currently calling object, which would be user in that case, which has already been exported earlier.

因此，似乎您将对象导出两次，导致抛出异常。

Hence, it seems you're exporting the object twice, resulting in the thrown exception.

请回答是否有帮助。祝你好运！

Please reply whether this helped or not. Good Luck!

这篇关于JAVA：RMI回调->对象已导出的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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