com.apollographql.apollo.internal.fetcher.CacheFirstFetcher Maven / Gradle / Ivy

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/**
 * Copyright 2018-2019 Amazon.com,
 * Inc. or its affiliates. All Rights Reserved.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

package com.apollographql.apollo.internal.fetcher;

import com.apollographql.apollo.exception.ApolloException;
import com.apollographql.apollo.fetcher.ResponseFetcher;
import com.apollographql.apollo.interceptor.ApolloInterceptor;
import com.apollographql.apollo.interceptor.ApolloInterceptorChain;
import com.apollographql.apollo.internal.ApolloLogger;

import java.util.concurrent.Executor;

import javax.annotation.Nonnull;

/**
 * Signals the apollo client to first fetch the data from the normalized cache. If it's not present in the normalized
 * cache or if an exception occurs while trying to fetch it from the normalized cache, then the data is instead fetched
 * from the network.
 */
public final class CacheFirstFetcher implements ResponseFetcher {

  @Override public ApolloInterceptor provideInterceptor(final ApolloLogger apolloLogger) {
    return new CacheFirstInterceptor();
  }

  private static final class CacheFirstInterceptor implements ApolloInterceptor {

    private volatile boolean disposed;

    @Override
    public void interceptAsync(@Nonnull final InterceptorRequest request, @Nonnull final ApolloInterceptorChain chain,
        @Nonnull final Executor dispatcher, @Nonnull final CallBack callBack) {
      InterceptorRequest cacheRequest = request.toBuilder().fetchFromCache(true).build();
      chain.proceedAsync(cacheRequest, dispatcher, new CallBack() {
        @Override public void onResponse(@Nonnull InterceptorResponse response) {
          callBack.onResponse(response);
        }

        @Override public void onFailure(@Nonnull ApolloException e) {
          if (!disposed) {
            InterceptorRequest networkRequest = request.toBuilder().fetchFromCache(false).build();
            chain.proceedAsync(networkRequest, dispatcher, callBack);
          }
        }

        @Override public void onCompleted() {
          callBack.onCompleted();
        }

        @Override public void onFetch(FetchSourceType sourceType) {
          callBack.onFetch(sourceType);
        }
      });
    }

    @Override public void dispose() {
      disposed = true;
    }
  }
}