Retrofit2使用CallAdapterFactory的错误处理

概述

在使用Retrofit1的时候有一个类叫ErrorHandler,可以方便的定义自己的异常处理，但是在Retrofit2中是没有这个类的，详情见讨论：How do we create ErrorHandler in retrofit 2.0? #1102

总结

在相关讨论之下发现了一种好的解决方案,详情见： Retrofit 2 and Rx Java call adapter error handling，主要通过CallAdapter.Factory 来实现，核心代码

• 定义CallAdapter

public class RxErrorHandlingCallAdapterFactory extends CallAdapter.Factory {
private final RxJavaCallAdapterFactory original;

private RxErrorHandlingCallAdapterFactory() {
        original = RxJavaCallAdapterFactory.create();
    }

public static CallAdapter.Factory create() {
return new RxErrorHandlingCallAdapterFactory();
    }

@Override
public CallAdapter<?> get(Type returnType, Annotation[] annotations, Retrofit retrofit) {
return new RxCallAdapterWrapper(retrofit, original.get(returnType, annotations, retrofit));
    }

private static class RxCallAdapterWrapper implements CallAdapter<Observable<?>> {
private final Retrofit retrofit;
private final CallAdapter<?> wrapped;

public RxCallAdapterWrapper(Retrofit retrofit, CallAdapter<?> wrapped) {
this.retrofit = retrofit;
this.wrapped = wrapped;
        }

@Override
public Type responseType() {
return wrapped.responseType();
        }

@SuppressWarnings("unchecked")
@Override
public <R> Observable<?> adapt(Call<R> call) {
return ((Observable) wrapped.adapt(call)).onErrorResumeNext(new Func1<Throwable, Observable>() {
@Override
public Observable call(Throwable throwable) {
return Observable.error(asRetrofitException(throwable));
                }
            });
        }

private RetrofitException asRetrofitException(Throwable throwable) {
// We had non-200 http error
if (throwable instanceof HttpException) {
// A network error happened
            }
if (throwable instanceof IOException) {
            }
// We don't know what happened. We need to simply convert to an unknown error
return RetrofitException.unexpectedError(throwable);
        }
    }
}

• 定义Exception

public class RetrofitException extends RuntimeException {
public static RetrofitException httpError(String url, Response response, Retrofit retrofit) {
        String message = response.code() + " " + response.message();
return new RetrofitException(message, url, response, Kind.HTTP, null, retrofit);
    }

public static RetrofitException networkError(IOException exception) {
return new RetrofitException(exception.getMessage(), null, null, Kind.NETWORK, exception, null);
    }

public static RetrofitException unexpectedError(Throwable exception) {
return new RetrofitException(exception.getMessage(), null, null, Kind.UNEXPECTED, exception, null);
    }
}

• 设置到Builder

new Retrofit.Builder()
        .baseUrl("your base url")
        .addConverterFactory(GsonConverterFactory.create(new Gson()))
        .addCallAdapterFactory(RxErrorHandlingCallAdapterFactory.create())
        .build();

• 错误处理

public void onError(Throwable throwable) {
if (throwable instanceof HttpException) {
// We had non-2XX http error
    }
if (throwable instanceof IOException) {
// A network or conversion error happened
    }

// We don't know what happened. We need to simply convert to an unknown error
// ...
  }

相关代码整理： retrofit2