MissingKotlinParameterException: due to missing (therefore NULL) value for creator parameter … which is a non-nullable type

We ran into the following issue when we tried to deserialize a JSON string coming from our Spring rest controller.

 FATAL EXCEPTION: main
    Process: com.example.driver, PID: 28305
    java.lang.IllegalStateException: Failed to load DataModel: com.fasterxml.jackson.module.kotlin.MissingKotlinParameterException: Instantiation of [simple type, class com.example.model.StorageDevice] value failed for JSON property storageDeviceId due to missing (therefore NULL) value for creator parameter storageDeviceId which is a non-nullable type
        at [Source: (okhttp3.ResponseBody$BomAwareReader); line: 1, column: 1764] (through reference chain: com.example.model.DataModel["storageDevices"]->java.util.ArrayList[0]->com.example.model.cargospace.StorageDevice["storageDeviceId"])
        at com.example.model.RestTourRepository$updateDataModel$1.onFailure(RestTourRepository.kt:38)
        at retrofit2.ExecutorCallAdapterFactory$ExecutorCallbackCall$1$2.run(ExecutorCallAdapterFactory.java:79)
        at android.os.Handler.handleCallback(Handler.java:751)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:154)
        at android.app.ActivityThread.main(ActivityThread.java:6121)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:889)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:779)

The object we try to construct looks like this:

@JsonIdentityInfo(
        generator = ObjectIdGenerators.PropertyGenerator::class,
        property = "storageDeviceId"
)
data class StorageDevice (
    val storageDeviceId: String,
    val configuration: AbstractStorageDeviceConfiguration,
    val storageDeviceLocation: StorageDeviceLocation
)

And the JSON string we receive is the following:

{
    "storageDeviceId": "71ba49f3-d8c8-425f-b7e4-29b8c49f417d",
    "id": 166,
    "configuration": {
        "storageDeviceConfigurationId": "c2c926b3-de70-491a-9f8d-514830d56a4b",
         …
    },
    "storageDeviceLocation": "1f64613b-6e96-4825-a489-faa00608516e",
    "new": false
}, …

We solved the issue by changing the val storageDeviceId: String to val storageDeviceId: String?. The value was then properly set after deserialization.

The question arises why we had to set it to nullable in the first place?

Versions: jackson-module-kotlin:2.9.0 jackson-annotations:2.9.0

[cowtowncoder]

@asarkar Please do note that this is a fully volunteer-based open source project. We all have our lives, and participation here has to compete with many other things which generally are more important (family for example). So although I trust you did not mean your comment to sound like it, it came across bit strong as if there was some entitlement to quick service, solely based on the fact that you would like to see it fixed. There is no service expectation, and asking for status updates is typically not very helpful in getting things to move.

[asarkar]

Of course there are no service guarantees, let alone entitlements. However, what is lacking here is the acknowledgement that the reported issue is a bug, and will be addressed in a future release. “this is open source” argument is too much of a cliche, isn’t it? I work with and contribute to open sources myself, and one thing I often see is a strong resistance and/or obliviousness to problem reports, and putting the onus squarely on the reporter as if it’s their fault having found an issue with the code.