class not found exception when sending objects through socket in java

Question

SimpleClient.java

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

class testobject implements Serializable {

    int value;
    String id;

    public testobject(int v, String s) {
        this.value = v;
        this.id = s;
    }
}

public class SimpleClient {

    public static void main(String args[]) {
        try {
            Socket s = new Socket("localhost", 2002);
            OutputStream os = s.getOutputStream();
            ObjectOutputStream oos = new ObjectOutputStream(os);
            testobject to = new testobject(1, "object from client");
            oos.writeObject(to);
            oos.writeObject(new String("another object from the client"));
            oos.close();
            os.close();
            s.close();
        } catch (Exception e) {
            System.out.println(e);
        }
    }
}

SimpleServer.java

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

class testobject implements Serializable {

    int value;
    String id;

    public testobject(int v, String s) {
        this.value = v;
        this.id = s;
    }
}

public class SimpleServer {

    public static void main(String args[]) {
        int port = 2002;
        try {
            ServerSocket ss = new ServerSocket(port);
            Socket s = ss.accept();
            InputStream is = s.getInputStream();
            ObjectInputStream ois = new ObjectInputStream(is);
            testobject to = (testobject) ois.readObject();
            if (to != null) {
                System.out.println(to.id);
            }
            System.out.println((String) ois.readObject());
            is.close();
            s.close();
            ss.close();
        } catch (Exception e) {
            System.out.println(e);
        }
    }
}

Are both classes in exactly the same package? Given that you have not declared a serialVersionUID, do both classes exactly the same content? More to the point; why not compile TestObject as a separate unit and use it in both the other projects? Finally classes in Java are always in PascalCase, no excuses. — Boris the Spider
– Boris the Spider, Commented Jul 30, 2016 at 12:41
You should make a JAR file for your "core" objects and use that as a library between your two projects. Don't make two separate Java classes that "look" the same — OneCricketeer
– OneCricketeer, Commented Jul 30, 2016 at 12:47

user207421 · Accepted Answer · 2016-07-31 02:05:14Z

2

From the fact that you've repeated the testobject class in your post, it is evident that you think you can use two copies of it. You can't. You have to use the same one at both ends, in the same package. Preferably the same binary.

NB readObject() only returns null if you sent a null.

edited Jul 31, 2016 at 2:05

answered Jul 30, 2016 at 12:49

user207421

312k45 gold badges324 silver badges493 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Eugene · Accepted Answer · 2016-07-30 13:29:20Z

0

As @EJP mentioned, the client and server should use same testobject class file.

To verify it, add System.out.println("From client: " + to) and System.out.println("From server: " + to) to print full path name of object combined both package name and Class name.

Also, you can use keyword instance of to make sure the class type of object is what you want before using it.

answered Jul 30, 2016 at 13:29

Eugene

11.2k7 gold badges57 silver badges72 bronze badges

Collectives™ on Stack Overflow

class not found exception when sending objects through socket in java

2 Answers 2

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related