retrofit2.HttpServiceMethod Maven / Gradle / Ivy

/*
 * Copyright (C) 2015 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package retrofit2;

import static retrofit2.Utils.getRawType;
import static retrofit2.Utils.methodError;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import javax.annotation.Nullable;
import kotlin.coroutines.Continuation;
import okhttp3.ResponseBody;

/** Adapts an invocation of an interface method into an HTTP call. */
abstract class HttpServiceMethod extends ServiceMethod {
  /**
   * Inspects the annotations on an interface method to construct a reusable service method that
   * speaks HTTP. This requires potentially-expensive reflection so it is best to build each service
   * method only once and reuse it.
   */
  static  HttpServiceMethod parseAnnotations(
      Retrofit retrofit, Method method, RequestFactory requestFactory) {
    boolean isKotlinSuspendFunction = requestFactory.isKotlinSuspendFunction;
    boolean continuationWantsResponse = false;
    boolean continuationBodyNullable = false;

    Annotation[] annotations = method.getAnnotations();
    Type adapterType;
    if (isKotlinSuspendFunction) {
      Type[] parameterTypes = method.getGenericParameterTypes();
      Type responseType =
          Utils.getParameterLowerBound(
              0, (ParameterizedType) parameterTypes[parameterTypes.length - 1]);
      if (getRawType(responseType) == Response.class && responseType instanceof ParameterizedType) {
        // Unwrap the actual body type from Response.
        responseType = Utils.getParameterUpperBound(0, (ParameterizedType) responseType);
        continuationWantsResponse = true;
      } else {
        // TODO figure out if type is nullable or not
        // Metadata metadata = method.getDeclaringClass().getAnnotation(Metadata.class)
        // Find the entry for method
        // Determine if return type is nullable or not
      }

      adapterType = new Utils.ParameterizedTypeImpl(null, Call.class, responseType);
      annotations = SkipCallbackExecutorImpl.ensurePresent(annotations);
    } else {
      adapterType = method.getGenericReturnType();
    }

    CallAdapter callAdapter =
        createCallAdapter(retrofit, method, adapterType, annotations);
    Type responseType = callAdapter.responseType();
    if (responseType == okhttp3.Response.class) {
      throw methodError(
          method,
          "'"
              + getRawType(responseType).getName()
              + "' is not a valid response body type. Did you mean ResponseBody?");
    }
    if (responseType == Response.class) {
      throw methodError(method, "Response must include generic type (e.g., Response)");
    }
    // TODO support Unit for Kotlin?
    if (requestFactory.httpMethod.equals("HEAD") && !Void.class.equals(responseType)) {
      throw methodError(method, "HEAD method must use Void as response type.");
    }

    Converter responseConverter =
        createResponseConverter(retrofit, method, responseType);

    okhttp3.Call.Factory callFactory = retrofit.callFactory;
    if (!isKotlinSuspendFunction) {
      return new CallAdapted<>(requestFactory, callFactory, responseConverter, callAdapter);
    } else if (continuationWantsResponse) {
      //noinspection unchecked Kotlin compiler guarantees ReturnT to be Object.
      return (HttpServiceMethod)
          new SuspendForResponse<>(
              requestFactory,
              callFactory,
              responseConverter,
              (CallAdapter>) callAdapter);
    } else {
      //noinspection unchecked Kotlin compiler guarantees ReturnT to be Object.
      return (HttpServiceMethod)
          new SuspendForBody<>(
              requestFactory,
              callFactory,
              responseConverter,
              (CallAdapter>) callAdapter,
              continuationBodyNullable);
    }
  }

  private static  CallAdapter createCallAdapter(
      Retrofit retrofit, Method method, Type returnType, Annotation[] annotations) {
    try {
      //noinspection unchecked
      return (CallAdapter) retrofit.callAdapter(returnType, annotations);
    } catch (RuntimeException e) { // Wide exception range because factories are user code.
      throw methodError(method, e, "Unable to create call adapter for %s", returnType);
    }
  }

  private static  Converter createResponseConverter(
      Retrofit retrofit, Method method, Type responseType) {
    Annotation[] annotations = method.getAnnotations();
    try {
      return retrofit.responseBodyConverter(responseType, annotations);
    } catch (RuntimeException e) { // Wide exception range because factories are user code.
      throw methodError(method, e, "Unable to create converter for %s", responseType);
    }
  }

  private final RequestFactory requestFactory;
  private final okhttp3.Call.Factory callFactory;
  private final Converter responseConverter;

  HttpServiceMethod(
      RequestFactory requestFactory,
      okhttp3.Call.Factory callFactory,
      Converter responseConverter) {
    this.requestFactory = requestFactory;
    this.callFactory = callFactory;
    this.responseConverter = responseConverter;
  }

  @Override
  final @Nullable ReturnT invoke(Object[] args) {
    Call call = new OkHttpCall<>(requestFactory, args, callFactory, responseConverter);
    return adapt(call, args);
  }

  protected abstract @Nullable ReturnT adapt(Call call, Object[] args);

  static final class CallAdapted extends HttpServiceMethod {
    private final CallAdapter callAdapter;

    CallAdapted(
        RequestFactory requestFactory,
        okhttp3.Call.Factory callFactory,
        Converter responseConverter,
        CallAdapter callAdapter) {
      super(requestFactory, callFactory, responseConverter);
      this.callAdapter = callAdapter;
    }

    @Override
    protected ReturnT adapt(Call call, Object[] args) {
      return callAdapter.adapt(call);
    }
  }

  static final class SuspendForResponse extends HttpServiceMethod {
    private final CallAdapter> callAdapter;

    SuspendForResponse(
        RequestFactory requestFactory,
        okhttp3.Call.Factory callFactory,
        Converter responseConverter,
        CallAdapter> callAdapter) {
      super(requestFactory, callFactory, responseConverter);
      this.callAdapter = callAdapter;
    }

    @Override
    protected Object adapt(Call call, Object[] args) {
      call = callAdapter.adapt(call);

      //noinspection unchecked Checked by reflection inside RequestFactory.
      Continuation> continuation =
          (Continuation>) args[args.length - 1];

      // See SuspendForBody for explanation about this try/catch.
      try {
        return KotlinExtensions.awaitResponse(call, continuation);
      } catch (Exception e) {
        return KotlinExtensions.suspendAndThrow(e, continuation);
      }
    }
  }

  static final class SuspendForBody extends HttpServiceMethod {
    private final CallAdapter> callAdapter;
    private final boolean isNullable;

    SuspendForBody(
        RequestFactory requestFactory,
        okhttp3.Call.Factory callFactory,
        Converter responseConverter,
        CallAdapter> callAdapter,
        boolean isNullable) {
      super(requestFactory, callFactory, responseConverter);
      this.callAdapter = callAdapter;
      this.isNullable = isNullable;
    }

    @Override
    protected Object adapt(Call call, Object[] args) {
      call = callAdapter.adapt(call);

      //noinspection unchecked Checked by reflection inside RequestFactory.
      Continuation continuation = (Continuation) args[args.length - 1];

      // Calls to OkHttp Call.enqueue() like those inside await and awaitNullable can sometimes
      // invoke the supplied callback with an exception before the invoking stack frame can return.
      // Coroutines will intercept the subsequent invocation of the Continuation and throw the
      // exception synchronously. A Java Proxy cannot throw checked exceptions without them being
      // declared on the interface method. To avoid the synchronous checked exception being wrapped
      // in an UndeclaredThrowableException, it is intercepted and supplied to a helper which will
      // force suspension to occur so that it can be instead delivered to the continuation to
      // bypass this restriction.
      try {
        return isNullable
            ? KotlinExtensions.awaitNullable(call, continuation)
            : KotlinExtensions.await(call, continuation);
      } catch (Exception e) {
        return KotlinExtensions.suspendAndThrow(e, continuation);
      }
    }
  }
}