BreakingGzipInterceptorTest.java

import org.junit.Rule;
import org.junit.Test;

import java.io.IOException;

import okhttp3.Call;
import okhttp3.Interceptor;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import okhttp3.mockwebserver.MockResponse;
import okhttp3.mockwebserver.MockWebServer;
import okio.Buffer;
import okio.GzipSink;
import okio.GzipSource;
import okio.Okio;

import static org.junit.Assert.assertEquals;

public class BreakingGzipInterceptorTest {

    @Rule
    public final MockWebServer server = new MockWebServer();

    @Test
    public void test() throws Exception {
        server.enqueue(new MockResponse()
                .addHeader("Content-Encoding", "gzip")
                .setBody(gzip("abc")));

        Request request = new Request.Builder()
                .url(server.url("/"))
                .build();

        OkHttpClient client = new OkHttpClient.Builder()
                .addNetworkInterceptor(new BreakingGzipInterceptor())
                .build();

        Call call = client.newCall(request);
        Response response = call.execute();

        assertEquals("abc", response.body().string());
    }

    private static class BreakingGzipInterceptor implements Interceptor {
        @Override
        public Response intercept(Chain chain) throws IOException {
            Request request = chain.request();
            Response response = chain.proceed(request);
            String contentEncoding = response.header("Content-Encoding");
            if (contentEncoding != null && contentEncoding.equalsIgnoreCase("gzip")) {
                // decompress and read the gzip encoded body, seems innocent enough...
                GzipSource source = new GzipSource(response.body().source());
                String body = Okio.buffer(source).readUtf8();
                System.out.println(body);
            }
            return response;
        }
    }

    private static Buffer gzip(String body) throws IOException {
        Buffer buffer = new Buffer();
        Okio.buffer(new GzipSink(buffer)).writeUtf8(body).close();
        return buffer;
    }
}