java.io.NotSerializableException with serializable data class in Kotlin (kotlinx.serialization)

Question

I'm facing java.io.NotSerializableException when trying to writeObject and object of a data class into an ObjectOutputStream. Following is the main activity function of my project :

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        debug()
    }
    fun debug() {
        val oos = ObjectOutputStream(ByteArrayOutputStream())
        val obj = BaseElement("HELLO WORLD")
        try{
            oos.writeObject(obj)
        }
        catch(e : Exception) {
            Log.d("mydebug", e.stackTraceToString())
        }
    }
}

The BaseElement class can be found here :

import kotlinx.serialization.Serializable

@Serializable
data class BaseElement(var sentence : String)

The stacktracke is as following :

java.io.NotSerializableException: com.example.myproject.model.BaseElement
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1240)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:354)
        at com.example.myproject.MainActivity.debug(MainActivity.kt:29)
        at com.example.myproject.MainActivity.onCreate(MainActivity.kt:17)
        at android.app.Activity.performCreate(Activity.java:8130)
        at android.app.Activity.performCreate(Activity.java:8110)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1343)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3781)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3977)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:109)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2374)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loopOnce(Looper.java:233)
        at android.os.Looper.loop(Looper.java:344)
        at android.app.ActivityThread.main(ActivityThread.java:8248)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:589)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1071)

Someone please help me understand the solution to this issue.

Surajkaran Meghwanshi · Accepted Answer · 2023-01-12 10:06:15Z

1

Implement the serializable interface

import kotlinx.serialization.Serializable


data class BaseElement(var sentence : String) : Serializable

answered Jan 12, 2023 at 10:06

Surajkaran Meghwanshi

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2 Comments

Vishal Mahavar Over a year ago

Thank you for pointing this out, but this is not completely correct. We won't need to import kotlinx serialization and the Serializable interface will be used from java.io Please update you answer to import java.io.*

Surajkaran Meghwanshi Over a year ago

yeah , both imports will work @VishalMahavar

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