20.1. What is Serialization?

Serialization is the process of converting the state of an object into a byte stream so that the byte stream can be reverted back into a copy of the original object.

Serialization takes an object, which is a data structure in memory, and transforms it into a format that can be easily stored or transported. This format is typically a sequence of bytes (the byte stream). When needed, the byte stream can be converted back into the original object. Essentially, it is about changing an object's memory representation into a form suitable for saving or sending over networks.

Think of serialization like packing items into a box for shipping. The items (the object) are safely packed into the box (the byte stream), and when the recipient receives the box, they can unpack it to retrieve the items in their original state.

• Save the state of an object to a storage medium.
• Send an object over a network using sockets or RMI.
• Cache objects.
• Clone or deep copy objects.

Serialization serves multiple purposes in programming. First, it allows the state of an object to be saved, meaning you can store the current information of that object somewhere persistent, like a file or a database. Second, it helps in sending objects between different parts of an application or even over networks, which is essential for remote communication. It can also be used to cache objects temporarily to improve access times, and it can provide a way to create exact duplicates of objects through cloning.

Imagine you want to save a progress in a game. Serialization is like saving your current game state to a file. This lets you come back later and load that state (deserialization) so you can continue playing from where you left off, just like the game remembers your score and position.

• Java RMI (Remote Method Invocation).
• Hibernate / JPA (object persistence frameworks).
• Android bundle data passing.
• Distributed systems and microservices.

Serialization is widely used in various technology frameworks and applications. For instance, in Java Remote Method Invocation (RMI), objects are serialized to be sent over a network so that methods can be invoked remotely. In object persistence frameworks like Hibernate or JPA, serialization helps in saving the state of objects to a database. In Android development, it’s utilized to pass data between activities or fragments through bundles. Furthermore, in distributed systems and microservices architectures, where applications are broken into smaller services that communicate over a network, serialization facilitates transferring data between these services.

Consider a delivery service that needs to send packages (objects) to different destinations (use cases). Just like how the service uses different vehicles (RMI, Hibernate, Android bundles, etc.) to ensure that all packages arrive safely and correctly at their destinations, serialization helps prepare these packages for transport over various communication channels.

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