通过java中的套接字发送对象

问题描述

我有2个java netbeans项目，一个是Server，另一个是Client。我有一个我创建的Message类，我希望将其传递给服务器，并在服务器上完成修改后返回到客户端。我在两个项目中都包含了Message类。我使用 ObjectOutputStream 和 ObjectInputStream 来传递对象。服务器和客户端之间的连接是正常的，当我从 ObjectInputStream 使用 readObject（）读取对象时，对象通过但在服务器上方法我输入将其转换为消息类。但是服务器会抛出 ClassNotFoundException 。它找不到Message类。我该如何解决这个问题？

客户代码：

  public void startClient（）{
 try {
 //创建套接字
套接字clientSocket = new Socket（HOST，PORT）; 
 //创建输入&输出流到服务器
 ObjectOutputStream outToServer = new ObjectOutputStream（clientSocket.getOutputStream（））; 
 ObjectInputStream inFromServer = new ObjectInputStream（clientSocket.getInputStream（））; 
 
 //读取修改
 // TODO这里
 
 / *创建发送消息对象* / 
 LinkedList<消息> msgList = new LinkedList<>（）; 
消息msg = new Message（）; 
 msg.setMessage（Kasun）; 
 msg.setIndex（1）; 
 msg.setAverage（5.5f）; 
 msgList.push（msg）; 
 
 / *将消息对象发送到服务器* / 
 outToServer.writeObject（msgList）; 
 
 / *从服务器* / 
中回复消息对象LinkedList<消息> inFromServerList = new LinkedList<>（）; 
消息msgFrmServer = null; 
 inFromServerList =（LinkedList< Message>）inFromServer.readObject（）; 
 msgFrmServer = inFromServerList.pop（）; 
 
 / *打印出已收到的Message * / 
 System.out.println（Message：+ msgFrmServer.getMessage（））; 
 System.out.println（Index：+ msgFrmServer.getIndex（））; 
 System.out.println（Average：+ msgFrmServer.getAverage（））; 
 
 
 clientSocket.close（）; 
 
} catch（例外e）{
 System.err.println（Client Error：+ e.getMessage（））; 
 System.err.println（Localized：+ e.getLocalizedMessage（））; 
 System.err.println（Stack Trace：+ e.getStackTrace（））; 
} 
} 
  

服务器代码

  public void startServer（）{
 
 try {
 ServerSocket welcomeSocket = new ServerSocket（PORT）; 
 
 while（true）{
 //创建客户端套接字
套接字clientSocket = welcomeSocket.accept（）; 
 System.out.println（Socket Extablished ...）; 
 //为客户端创建输入和输出流
 ObjectOutputStream outToClient = new ObjectOutputStream（clientSocket.getOutputStream（））; 
 ObjectInputStream inFromClient = new ObjectInputStream（clientSocket.getInputStream（））; 
 
 //读取修改
 // TODO这里
 
 / *创建消息对象和反向信息* / 
 LinkedList<消息> inList = new LinkedList<>（）; 
消息inMsg = null; 
 inList =（LinkedList< Message>）inFromClient.readObject（）; 
 inMsg = inList.pop（）; 
 
 / *修改消息对象* / 
 inMsg.setMessage（inMsg.getMessage（）。toUpperCase（））; 
 inMsg.setIndex（5）; 
 inMsg.setAverage（10.5f）; 
 
 / *将修改后的Message对象发回* / 
 outToClient.writeObject（inMsg）; 
 
} 
 
} catch（例外e）{
 System.err.println（服务器错误：+ e.getMessage（））; 
 System.err.println（Localized：+ e.getLocalizedMessage（））; 
 System.err.println（Stack Trace：+ e.getStackTrace（））; 
 System.err.println（To String：+ e.toString（））; 
} 
} 
  

服务器抛出的异常

  java.lang.ClassNotFoundException：rusl.online.examination.system.client.utility.Message 
  

我是否必须使用java RMI？有没有使用RMI的解决方案？

解决方案

确保服务器端的消息是 rusl .online.examination.system.client.utility.Message 。似乎并非如此。

I have 2 java netbeans projects, one is the Server other is the Client. I have a Message class that I have created which I want to pass to the server and back the other way to the client after modification done at the server. I have included the class Message in both projects. I use ObjectOutputStream and ObjectInputStream to pass the object. The connection between the server and the client is ok and the object passes through but at the server when I read the object from the ObjectInputStream using readObject() method I type cast it to the Message class. But an ClassNotFoundException is thrown at the server. It cant find the Message class. How can I resolve this?

Code for the client:

public void startClient() {
    try {
        // Create the socket
        Socket clientSocket = new Socket(HOST, PORT);
        // Create the input & output streams to the server
        ObjectOutputStream outToServer = new ObjectOutputStream(clientSocket.getOutputStream());
        ObjectInputStream inFromServer = new ObjectInputStream(clientSocket.getInputStream());

        // Read modify
        // TODO here

        /* Create The Message Object to send */
        LinkedList<Message> msgList = new LinkedList<>();
        Message msg = new Message();
        msg.setMessage("Kasun");
        msg.setIndex(1);
        msg.setAverage(5.5f);
        msgList.push(msg);

        /* Send the Message Object to the server */
        outToServer.writeObject(msgList);

        /* Retrive the Message Object from server */
        LinkedList<Message> inFromServerList = new LinkedList<>();
        Message msgFrmServer = null;
        inFromServerList = (LinkedList<Message>)inFromServer.readObject();
        msgFrmServer = inFromServerList.pop();

        /* Print out the recived Message */
        System.out.println("Message: " + msgFrmServer.getMessage());
        System.out.println("Index: " + msgFrmServer.getIndex());
        System.out.println("Average: " + msgFrmServer.getAverage());


        clientSocket.close();

    } catch (Exception e) {
        System.err.println("Client Error: " + e.getMessage());
        System.err.println("Localized: " + e.getLocalizedMessage());
        System.err.println("Stack Trace: " + e.getStackTrace());
    }
}

Code for the Server

public void startServer() {

    try {
        ServerSocket welcomeSocket = new ServerSocket(PORT);

        while (true) {
            // Create the Client Socket
            Socket clientSocket = welcomeSocket.accept();
            System.out.println("Socket Extablished...");
            // Create input and output streams to client
            ObjectOutputStream outToClient = new ObjectOutputStream(clientSocket.getOutputStream());
            ObjectInputStream inFromClient = new ObjectInputStream(clientSocket.getInputStream());

            // Read modify
            // TODO here

            /* Create Message object and retrive information */
            LinkedList<Message> inList = new LinkedList<>();
            Message inMsg = null;
            inList = (LinkedList<Message>)inFromClient.readObject();
            inMsg = inList.pop();

            /* Modify the message object */
            inMsg.setMessage(inMsg.getMessage().toUpperCase());
            inMsg.setIndex(5);
            inMsg.setAverage(10.5f);

            /* Send the modified Message object back */
            outToClient.writeObject(inMsg);

        }

    } catch (Exception e) {
        System.err.println("Server Error: " + e.getMessage());
        System.err.println("Localized: " + e.getLocalizedMessage());
        System.err.println("Stack Trace: " + e.getStackTrace());
        System.err.println("To String: " + e.toString());
    }
}

The exception thrown at the "server"

java.lang.ClassNotFoundException: rusl.online.examination.system.client.utility.Message

Would I have to use java RMI? Is there a solution for this without using RMI?

解决方案

Make sure that Message on server side is rusl.online.examination.system.client.utility.Message. It seems not to be the case.

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