Question

topics和subs是由远程字符串填充的两个私有ArrayList和ISubs（接口）

private synchronized void notify(MyMessage msg){
    for(int i=0; i<topics.size(); i++){
        if(topics.get(i).equalsIgnoreCase(msg.getTopic())){
            try {
                subs.get(i).getListener().onMessage(msg);
            } catch (RemoteException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
}

{p} notify()由publish(MyMessage msg)方法调用，它获取一个远程MyMessage对象

 public boolean publish(MyMessage msg) throws RemoteException {

    if(!total.tryAcquire()){
        System.out.println("Publish respinta");
        return false;
    }

    try {
        concurrent.acquire();

        mutex.acquire();
        FileWriter file = new FileWriter("messaggi.txt",true);
        BufferedWriter bw = new BufferedWriter(file);
        bw.write(msg.getTopic()+": "+msg.getContenuto());
        bw.newLine();
        bw.flush();
        bw.close();
        mutex.release();

        notify(msg);

    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } finally{
        concurrent.release();
        total.release();
    }
    return true;
}

每次调用publish()时，我都会遇到以下异常：

java.lang.NullPointerException at server.MessageServer.notify（MessageServer.java:87）at server.MessageServer.publish（MessageServer.java:61）at sun.reflect.NativeMethodAccessorImpl.invoke0（Native Method）at sun.reflect.NativeMethodAccessorImpl.invoke（未知来源）at sun.reflect.DelegatingMethodAccessorImpl.invoke（未知来源）at java.lang.reflect.Method.invoke（未知来源）at sun.rmi.server.UnicastServerRef.dispatch（未知来源）at sun.rmi.transport.Transport $ 1.run（未知来源）at sun.rmi.transport.Transport $ 1.run（未知来源）at java.security.AccessController.doPrivileged（Native Method）at sun.rmi.transport.Transport.serviceCall（未知来源）at sun.rmi.transport.tcp.TCPTransport.handleMessages（未知来源）at sun.rmi.transport.tcp.TCPTransport $ ConnectionHandler.run0（未知来源）at sun.rmi.transport.tcp.TCPTransport $ ConnectionHandler.lambda $运行$ 0（未知来自java.security.AccessController.doPrivileged（Native Method） at sun.rmi.transport.tcp.TCPTransport $ ConnectionHandler.run（未知来自）java.util.concurrent.ThreadPoolExecutor.runWorker（未知来自java.util.concurrent.ThreadPoolExecutor $ Worker.run（未知来自）java.lang.Thread.run（未知来源）at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer（未知来源）在sun.rmi.transport.StreamRemoteCall.executeCall（未知来源）在sun.rmi.server.UnicastRef.invoke（未知来源）at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod（未知来源）at java.rmi.server.RemoteObjectInvocationHandler.invoke（未知来源）在com.sun.proxy。$ Proxy0.publish（未知来源）at publisher.PublisherThread.run（PublisherThread.java:22）

显然topics和subs在调用publish()之前填充。

编辑：好的，我发现了这个问题，请不要杀了我，我忘了在Subscriber构造函数中初始化MsgListener。

远程回调方法引发Java NullPointerException - Java RMI

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