Serialization in Android – A Detailed Explanation

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📘 What is Serialization?

Serialization is the process of converting an object into a format that can be stored or transmitted — like a file, bundle, or over the network. The opposite process, deserialization, is converting that format back into an object.

Think of serialization like converting a real-life object into a string or byte stream so it can be saved, transferred, or shared.

📱 Why is Serialization Used in Android?

In Android, serialization is used for several reasons:

🔍 Key Characteristics of Serialization:

• Converts an in-memory object into a format like:
• The format must be restorable, meaning the object can be reconstructed exactly as it was.

📦 How Serialization Works (Conceptually)

Let’s say you have this data class:

data class User(val name: String, val age: Int)        

When you serialize this:

• It might become a byte stream or a JSON string like:

{"name": "John", "age": 25}        

🛠️ Types of Serialization in Android (Overview)

🧪 Detailed Explanation of Each Type

1. 🧱 Java Serialization (Serializable)

• Uses java.io.Serializable
• Very simple to implement
• Not efficient for Android (slow, uses reflection)

import java.io.Serializable

data class User(val name: String, val age: Int): Serializable        

Used in:

intent.putExtra("user", user)
val user = intent.getSerializableExtra("user") as? User        

🟥 Downside: Not optimized for Android (poor performance on large objects or lists).

2. ⚡ Android Parcelable

• Optimized for Android
• Uses Parcel for marshalling/unmarshalling
• Required for sending complex objects via Intent, Bundle

import android.os.Parcelable
import kotlinx.parcelize.Parcelize

@Parcelize
data class User(val name: String, val age: Int): Parcelable        

Used in:

intent.putExtra("user", user)
val user = intent.getParcelableExtra<User>("user")        

✅ Recommended for Android UI component communication

3. 🌐 JSON Serialization (Gson, Moshi, kotlinx.serialization)

• Converts objects to JSON strings
• Easy to read, good for APIs and storage

Using Gson:

val gson = Gson()
val json = gson.toJson(User("Tom", 28)) // Serialization
val user = gson.fromJson(json, User::class.java) // Deserialization        

Using kotlinx.serialization:

@Serializable
data class User(val name: String, val age: Int)

val json = Json.encodeToString(User("Tom", 28))
val user = Json.decodeFromString<User>(json)        

✅ Great for:

• Network APIs
• Saving to files
• Syncing with backend

🔄 Serialization vs Deserialization

📚 Real-World Example

Let’s say you're working on a chat app. You receive this JSON:

{"sender": "Alice", "message": "Hello!", "timestamp": 1615207200}        

You can:

1. Deserialize it into a Message class
2. Use it in your UI
3. Serialize the object when sending back a message

✅ Summary

• Serialization allows objects to be converted into a savable or transferrable format.
• In Android, it's crucial for communication between components and interacting with remote APIs.
• Use Parcelable for UI navigation, and JSON serialization (Gson, Moshi, kotlinx) for network and storage.