通过java中的套接字发送对象 [英] Sending an object through a socket in java
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问题描述
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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