Andorid - Getting error response body with retrofit and moshi using kotlin

Date : 15 / 11 / 2018

Hi,

Recently I was assigned to get a response error object using retrofit. Although there were some artciles and SO questions regard to this, I hardly find a usage  of  Kotlin, Retrofit and Moshi combination. Therefore I am writing this blog how to use this combination.
(I'm showing my actual working code here and the code should be self-explanatory. I am putting notes under every code snippet where necessary and explain a bit more)

So this is the response which I get when something goes wrong.

Here is the error response class which is reusable.

 @JsonClass(generateAdapter = true)  
 data class BaseResponse<T>(  
     @Json(name = "statusCode") val statusCode: Int,  
     @Json(name = "result") val result: T? = null,  
     @Json(name = "errorCode") val errorCode: String? = null  
 )  

Here is the JsonParser class which is responsible for json converting.

 class JsonParser {  
   fun moshi() = Moshi.Builder().build()  
   inline fun <reified T> toBaseResponseError(json: BufferedSource): BaseResponse<T>? {  
     return BaseResponseJsonAdapter<T>(moshi(), arrayOf(T::class.java)).fromJson(json)  
   }  
  // other json converters  
 }  

Here is how to use that error response converter object.

 Service(this, Utils().getAccessToken(this)).getUser(  
       object : retrofit2.Callback<BaseResponse<HealthPersonInfo>> {  
         override fun onFailure(call: Call<BaseResponse<HealthPersonInfo>>, t: Throwable) {  
           hideProgress()  
         }  
         override fun onResponse(  
           call: Call<BaseResponse<HealthPersonInfo>>,  
           response: Response<BaseResponse<HealthPersonInfo>>  
         ) {  
           hideProgress()  
           if (response.isSuccessful) {  
             response.body()?.let {  
                // do what you need when the call is success  
             }  
           } else {  
             response.errorBody()?.let {  
               val errorResponse = JsonParser().toBaseResponseError<HealthPersonInfo>(it.source())  
               // now you have an error object(errorResponse ) and you can use it's properties as follows  
               val code = errorResponse?.errorCode  
             }  
           }  
         }  
       })  

Note : The "Service" class is responsible for creating retrofit builder. It has methods like "getUser" which constructs get user url and callback. "HealthPersonInfo" is a class which is used when we have a successful return.


Hope you can get something helpful. Happy coding!!!