Can java serializable objects pass between different classloaders?

Question

Recently I learn the java program language.I am curious about the java serializable and have a little doubts about it.

Can java serializable objects pass between different classloaders? What's the theory?

Answer 1

A "serializable object" can't, but you can serialize the object, and save the data anywhere. At some future point, on the same machine or a different one, in the same VM or a different one, in the same classloader or a different one, you can deserialize the saved data back into an object.

Answer 2

Just by implementing the Serializable interface won't allow you to "pass between different classloaders" . You need to write code to persist the serialized object to disk, and then on the other classloader (process) deserialize it. here's an example, taken from http://www.javapractices.com/topic/TopicAction.do?Id=57 :

    Car car = new Car();
    ....

    //serialize an object called it car to a file called car.ser.
    try (
      OutputStream file = new FileOutputStream("car.ser");
      OutputStream buffer = new BufferedOutputStream(file);
      ObjectOutput output = new ObjectOutputStream(buffer);
    ){
      output.writeObject(car); // this call writes file to disk
    }  
    catch(IOException ex){
      logger.log(Level.SEVERE, "Cannot perform output.", ex);
    }

To deserialize the object on the other end/classloader/jvm process you can do this:

 try(
      InputStream file = new FileInputStream("car.ser");
      InputStream buffer = new BufferedInputStream(file);
      ObjectInput input = new ObjectInputStream (buffer);
    ){
      //deserialize the List
      Car car = (Car)input.readObject();
      //display its data
      System.out.println("Recovered Car: " + car);

    }
    catch(ClassNotFoundException ex){
      logger.log(Level.SEVERE, "Cannot perform input. Class not found.", ex);
    }
    catch(IOException ex){
      logger.log(Level.SEVERE, "Cannot perform input.", ex);
    }

EDIT: In order to pickup serialized files and deserialize them, you can use a WatchService