RTSJ (Real-Time Specification for Java) extends and adapts the Java technology in order to allow the development of real time systems. In RTSJ the requirements of distributed systems were not considered. The serialization in Java is an example of a basic operation that needs to be reviewed to make distributed Java fully predictable and suitable for hard-real time systems. However, the most recent works in the application of Java in distributed real-time systems do not specify how a serialization process must be used in order to obtain a deterministic behavior. This paper describes a new serialization process focused on hard real-time systems which provide full time and space predictability.