How do I handle response errors using with Retrofit and RxJava/RxAndroid?

Question

I am having trouble working out how to handle a response error with retrofit and RxAndroid. onError() gets called if there is a network error or the like but I need to be able to get the response to check if there was an authentication error. Instead what I get is a token with a null String and I can't find out why. What is the best way to go about this?

This is my RxAndroid call at the moment.

    Client.getInstance().getService()
            .getToken(usernameET.getText().toString(), passwordET.getText().toString())
            .subscribe(new Subscriber<SiteInfo>() {
                @Override
                public void onCompleted() {

                }

                @Override
                public void onError(Throwable e) {
                    e.printStackTrace();
                }

                @Override
                public void onNext(SiteInfo siteInfo) {
                    Log.d(TAG, "onNext "+ token.toString());
                }
            });

This is my retrofit service

@GET("my_url_here")
Observable<Token> getToken(
        @Query("username") String username,
        @Query("password") String password
);

This is my Current restadapter

RestAdapter restAdapter = new RestAdapter.Builder()
            .setLogLevel(RestAdapter.LogLevel.FULL)
            .setEndpoint(BASE_URL)
            .build();

service = restAdapter.create(MyService.class);

And this is my Token Class.

public class Token {
    private String token;

    public String getToken() {
        return token;
    }

    public void setToken(String token) {
        this.token = token;
    }

    @Override
    public String toString() {
        return token;
    }
}

How should I go about handlng this. Can it be done in the RxAndroid part or do I need to add something to my RestClient or maybe something else entirely?

Thanks.

Edit

07-01 06:38:04.562    1680-1793/uk.co.dyolo.thing D/Retrofit﹕ ---> HTTP GET my_website_here
07-01 06:38:04.562    1680-1793/uk.co.dyolo.thing D/Retrofit﹕ ---> END HTTP (no body)
07-01 06:38:04.610    1680-1793/uk.co.dyolo.thing D/Retrofit﹕ <--- HTTP 200 my_website_here (48ms)
07-01 06:38:04.610    1680-1793/uk.co.dyolo.thing D/Retrofit﹕ : HTTP/1.1 200 OK

Answer 1

I have found a solution

Firstly I expanded my Token object to have an error property.

public class Token {

    private String token;
    private String error;

    public String getToken() {
        return token;
    }

    public void setToken(String token) {
        this.token = token;
    }

    public String getError() {
        return error;
    }

    public void setError(String error) {
        this.error = error;
    }

    @Override
    public String toString() {
        return token;
    }
}

Then I added an operator to my RxJava chain which can check to see if the error field is not null. And if there is an error, throw a custom exception which calls the subscribers onError allowing me to handle it.

if (token.getError() != null) {
    throw OnErrorThrowable.from(new UserAuthenticationException(token.getError()));
    }

And if there is an error, throw a custom exception which calls the subscribers onError allowing me to handle it.

if (e instanceof OnErrorThrowable){
    if (e.getCause() instanceof UserAuthenticationException){
        Log.d(TAG, "onError "+e.getCause().getMessage());
    }
    e.getCause().printStackTrace();
}

Answer 2

This is a bit late but if anyone wanders here, Retrofit 2 passes in instance of HttpException into the onError callback whenever the request returned from the server with an error code outside the [200,300) interval ...

throwable -> {
    if(throwable instanceof HttpException){
        switch(((HttpException)throwable).code()){
            // your error handling logic 
        }
    }
}

You can also retrieve the whole reponse from this object..