Question

(I know this can be done in RMI, but I need to do this using sockets since I found there could be some setup process if RMI methods used)

Please have a look at the simple Client-Server code at http://www.coderanch.com/t/205325/sockets/java/send-any-java-Object-through

In this program, the order two objects sent by SimpleServer are known by SimpleClient.

i.e: Server

oos.writeObject(new testobject(1,"object from client"));
oos.writeObject(new String("another object from the client"));

Client does the casting according to the order the object is received.But I want to avoid this nature and make client send any object at any time so the server should also be able to handle each object sent accordingly and return a result.

testobject to = (testobject)ois.readObject(); 
System.out.println(to.id);}  
System.out.println((String)ois.readObject());

Is there a way to “label” the objects being sent so that the action can be determined by a simple “if” statement in Server?

OR

is there a better way to use a ResultSet returned by the Server instead of my object serializing approach?

thanks in advance.

Thanks

Answer 1

readObject will return an object in its proper class. if you need to have some branching logic based on that you can use instanceof:

Object newObj = stream.readObject();
if (newObj instanceof testobject) {
     doSomething((testobject) newObj);
} else if (newObj instanceof String) {
     doSomethingWithString((String) newObj);
} // etc.

As a rule, this is not recommended for all objects read from a stream. If you’re going to use ObjectStreams to establish a protocol, you should document it and stick to it. That way, if one side sends incorrect data, you’ll catch it more quickly on the other side.

However, in a scenario where at a given point in the protocol flow, it’s expected that the client might be sending one of several different types of objects, then it might make sense.