通过套接字发送时对象丢失了数据

Question

Im trying to send an object back and forth between a client and server and when it leaves the client, all the data is there, ie z = 6.0 but when it reaches the server, all the data is reset, ie z = 0.0

I though it might of had something to do with me initializing variable in the object so I don't initialize anything, I also have added a constructor but nothing seems to work.

Object:

public class PlayerData implements Serializable{

String name;
int id;
double x,y,z;
double rotation;

PlayerData(String name, double x, double y, double z) {
    this.name = name;
    this.x = x;
    this.y = y;
    this.z = z;
    id = -1;
}
}

Client Sending:

        Thread t = new Thread(){
        public void run() {
            while(true){
                try{
                    System.out.println("Client writing player z: " + player.z);
                    streamOut.writeObject(player);
                    streamOut.flush();
                }catch(Exception ioe){
                    System.out.println("Sending Error: "+ ioe.getMessage());
                }
            }
        }
    };
    t.start();      

Server:

boolean done = false;
            while(!done) {
                //if(streamIn.available() > 0)
                try {
                    Object o = streamIn.readObject();
                    if(o instanceof PlayerData){
                        PlayerData recieved  = (PlayerData) o;
                        System.out.println("S: obj recieved z " + recieved.z);
                        for(int i = 0; i < serv.clientOut.size(); i++) {
                            serv.clientOut.get(i).writeObject(recieved);
                            serv.clientOut.get(i).flush();
                        }
                    }else 
                        System.out.println("Server: bad object");
                }
                catch(IOException e) {
                    done = true;
                }
            }

And it will say

Client writing player z: -42.05979919433594
S: obj recieved z 0.0

Answer 1

You're repeated sending the same object via serialization - and ObjectOutputStream notices that, and instead resolves this to references to the same object.

If you want to effectively send a separate object on each call, add this to your loop:

streamOut.reset();

That way, every time you write the object, it will write it out as if it's never seen it before (and you'll get a new object on each readObject call on the other side). Of course, that means the stream will be a lot bigger. Personally I'd consider using an alternative serialization technique such as Protocol Buffers, but that's a different matter...