Android Kotlin - 将 Gson 铸造的 API 数据存储到房间数据库中

Question

I am using okhttp to fetch Json data from an API, casting it into Gson for some other purposes, and at the same time, storing of the API data into a Room Database . (It can be storing of the API json data itself, or the casted Gson version) However, I am unsuccessful in this, and hope you could point me to the direction where I am going wrong.

I think i'm missing a typeConverter to convert the data retrieved from API and casted into GSON , to be stored in the Room database . But i'm not sure if i'm correct in this, or if my approach is correct in the first place.

Or could it be an issue with the fact that I have an Entities data class , but gsonData is casted into SampleData data class ?

DataGetter

...
...
...
// this suspend function is run within a coroutine.
private suspend fun APICall(url: String, pageNumber: Int, context: Context){
    val urlRequest = Request.Builder().url(url).build()  // Building of the URL to fetch data
    httpClient.newCall(urlRequest).enqueue(object : Callback {
        // onFailure -> cutting this out to shorten code
        // onResponse is where I am fetching the data and calling put to DB
        override fun onResponse(call: Call, response: Response) {
            val dataString = response.body!!.string()
            val gsonData = gsonResult.fromJson(dataString, SampleData::class.java)
            // Do some other stuffs with gsonData separately. This doesn't return anything to gsonData. 
            putToRoomDb(gsonData, context)  // This will eventually be done via another coroutine.
        }
    }
}

private suspend fun putToRoomDb(sampleData: SampleData, context: Context) {        
    val db = MyOnlyDatabase.getInstance(context)
    db.MyOnlyDao().updateOrInsert(sampleData)
}

Entity

@Entity(tableName = "sample_data_code_names")
data class SampleDataEntities(
    @PrimaryKey
    var Code: Int,
    val Name: String,
    val Description: String,
    val Item1: String,
    val Item2: String
) 

Dao

@Dao
interface SampleDataDao {
    @Insert(onConflict = OnConflictStrategy.REPLACE)
    suspend fun updateOrInsert(sampleDataEntities: SampleDataEntities)
}

Database

@Database(entities = [SampleDataEntities::class], version = 1, exportSchema = false)
abstract class MyOnlyDatabase: RoomDatabase() {
    abstract fun sampleDataDao(): SampleDataDao 

    companion object {  
        @Volatile
        private var instance: MyOnlyDatabase? = null    
        fun getInstance(context: Context): MyOnlyDatabase{
            return instance ?: synchronized(this) {                   
                instance ?: buildDatabase(context).also { instance = it }
            }
        }

        private fun buildDatabase(context: Context): MyOnlyDatabase{
            return Room.databaseBuilder(context, MyOnlyDatabase::class.java, "MyOnlyDatabase.db")
                .fallbackToDestructiveMigration()                   
                .build()                                                     
        }
    }
}

Note : Below is the data class for which gsonData is casted into.

data class SampleData(val value: List<SampleDataInfoItems>)
data class SampleDataInfoItems(
    val Code: String,
    val Name: String,
    val Description: String,
    val Item1: BigDecimal,
    val Item2: BigDecimal
)

Answer 1

You are not annotating your fields according to the JSON response that is coming from the server.

data class SampleDataInfoItems(
    @SerializedName("name_this_field_on_json")
    val Code: String,
    @SerializedName("and_so_on_for_all_fields")
    val Name: String,
    val Description: String,
    val Item1: BigDecimal,
    val Item2: BigDecimal
)

Also I think you need the GsonConververFactory for Retrofit.