Question

我有一个客户端将一个类对象发送到服务器。服务器应该调用该类的方法并返回结果。我运行程序时遇到以下异常java.lang.ClassNotFoundException：newclient.TestObject。

server.java：

package newserve;

import java.net.*;
import java.io.*;
import java.lang.reflect.*;

public class SERVER {
    public static void main(String[] args) {
    int port = 9876;
        try {
          ServerSocket ss = new ServerSocket(port);
      Socket s = ss.accept();

          InputStream is = s.getInputStream();
      ObjectInputStream ois = new ObjectInputStream(is);

      //read the first object from the socket
      Object o1 = /*(Object)*/ois.readObject();

          //Handling the first received object
      if (o1 != null){
        System.out.println("\nFROM SERVER - receiving class: " +
                                      o1.getClass().getName());
    System.out.println("\nWith these methods: \n" );

    //get all the methods into an array
    Method[] methods = o1.getClass().getDeclaredMethods();

    //print the methods
    for(int i = 0; i < methods.length; i++)
      System.out.println(methods[i]);

    //invoking the first method with default constructor
    Object a = methods[0].invoke(o1.getClass().newInstance(),
                                          new Object[] {3, 5});

    System.out.println("\nOutput of the first method: " + a);
  }

  //read the second object from the socket
  Object o2 = ois.readObject();
  System.out.println("\n\nFROM SERVER - receiving class: " +
                                      o2.getClass().getName());
  System.out.println("\nWith these: " + o2);

  //close everything and shut down
  is.close(); //close input stream
  s.close();  //close the socket
  ss.close(); //close the server's socket

}catch(Exception e){System.out.println(e);}
}

}

client.java：

package newclient;

import java.net.*;
import java.io.*;

public class CLIENT {
    public static void main(String[] args) {
        int port = 9876;
    try{
      Socket s = new Socket("localhost", port);
      OutputStream os = s.getOutputStream();
      ObjectOutputStream oos = new ObjectOutputStream(os);

      Object to = new TestObject(); //create a new object

      oos.writeObject(to); //send the object to the server

      //    create a new String object and send
      oos.writeObject(new String("A String object from client"));

      //close the connection
      oos.close();
      os.close();
      s.close();
    }catch(Exception e){System.out.println(e);}
  }
}

TestObject.java：

package newclient;

import java.io.*;

/**
* A test object to send via socket
*/
class TestObject implements Serializable {
  static final long serialVersionUID = 0;
  //constructor
  public TestObject(){};//default constructor

  //method
  public int add(int a, int b){return a+b;}
  public int sub(int a, int b){ return a-b;}
}

谢谢！

Answer 1

您的服务器在其类路径中需要newclient.TestObject.class。

您的目录结构应该是这样的：

(CWD)
├── newclient
│   ├── CLIENT.class
│   └── TestObject.class
└── newserver
    └── SERVER.class

其中CWD是当前工作目录。你应该站在那个顶级目录并运行

java -classpath . newserver.SERVER

Answer 2

我假设客户端和服务器程序在不同的机器上运行。然后，因为nos说你需要添加到服务器的类路径。

您的客户应该看起来像这样

    (CWD)
├── newclient
│   ├── CLIENT.class
│   └── TestObject.class

你应该像这样开始

java -classpath . newclient.CLIENT.class

您的服务器应该如下所示（注意它需要TestObject.class）

(CWD)
├── newclient
│   └── TestObject.class
└── newserver
    └── SERVER.class

你应该像这样开始

java -classpath。 newserver.CLIENT.class

java服务器没有从客户端接收对象

2 个答案: