Retrofit Error: How would I go about deserializing any kind of response from the server?

Question

I am using retrofit for android has been working great but I was wondering if there is a better solution to my problem.

Background

So I have a backend server which may respond with a server related error message in JSON form (not network) like "could not find ID X" etc.

It looks like this

{
      "data": {
        "errors": {
          "base": [
            "You could do the following because of blah blah"
          ]
        }
      }
    }

So the problem is the JSON error object which contains the array "base" might NOT be called "base" it could be called something else completely different. My backend has many kind of error response message name which cannot be changed so easily.

My question, it is possible to deserializise this JSON array without having to know its name in advance.

So far I have been doing this which is becoming a pain.

public class MyRetrofitError
{

    @SerializedName(JsonConstants.ERROR_KEY)
    private Errors errors;


    public Errors getErrors() {
        return errors;
    }

    public void setErrors(Errors errors) {
        this.errors = errors;
    }

    public static class Errors
    {
        private String errorMessage;
        private ErrorCodes errorCodes;

        public enum ErrorCodes{
            BOOKED_OVER_20,PROMO_CODE_FAILED;
        }

        @SerializedName("booked_over")
        private ArrayList<String> bookedOver= new ArrayList<String>();

        @SerializedName("promo_fail")
        private ArrayList<String> promoFailed= new ArrayList<String>();

        public String getErrorMessage() {
            if(promoFailed!= null && promoFailed.size() > 0) {setErrorMessage(promoFailed().get(0)); errorCodes = ErrorCodes.PROMO_CODE_FAILED;}
            if(bookedOver!= null && bookedOver.size() > 0){setErrorMessage(bookedOver().get(0)); errorCodes = ErrorCodes.BOOKED_OVER_20; }

            return errorMessage;
        }

        private void setErrorMessage(String errorMessage) {
            this.errorMessage = errorMessage;
        }

        public ErrorCodes getErrorCodes() {
            return errorCodes;
        }
    }


}

Please note: the root "data" object is not present in this, its handled else where via generics so I omitted it for this question

And then I would use the retrofit Error class getBodyAs method to map the incoming error to this model.

Is their a better way? Please note the backend is beyond my control.

score 1 · Accepted Answer · edited May 23 '17 at 12:08

Assuming you are using Gson with Retrofit (it is default). You can write a Custom Gson Deserializer for your errors class and save however you would like.

Here is a quick example to give you the idea (not tested)

// Possible error class
public static class Errors {
  Map<String, List<String>> errors;
  public void addErrors(String key, List<String> issues) {
     errors.put(key, issues);
  }
}

class ErrorDeserialzer implements JsonDeserializer<Errors> {

  @Override
  public Errors deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
  throws JsonParseException {
    Set<Map.Entry<String, JsonElement>> entries = jsonElement.getAsJsonObject().entrySet();
    for (Map.Entry<String, JsonElement> issues : entries) {
        List<String> values = new ArrayList<>();
        for (JsonElement value : issues.getValue().getAsJsonArray()) {
            values.add(value.getAsString());   
        }
        errors.add(issues.getKey(), values);
    }
    return errors;
  }
}

EDIT I also just found this link which may be of help

Retrofit Error: How would I go about deserializing any kind of response from the server?

1 Answers1