retrofit解析

retrofit解析

1.retrofit build

 /**     * Set the API base URL.     *     * @see #baseUrl(HttpUrl)     */    public Builder baseUrl(String baseUrl) {      checkNotNull(baseUrl, "baseUrl == null");      HttpUrl httpUrl = HttpUrl.parse(baseUrl);      if (httpUrl == null) {        throw new IllegalArgumentException("Illegal URL: " + baseUrl);      }      return baseUrl(httpUrl);    }    public Builder baseUrl(HttpUrl baseUrl) {      checkNotNull(baseUrl, "baseUrl == null");      List<String> pathSegments = baseUrl.pathSegments();      if (!"".equals(pathSegments.get(pathSegments.size() - 1))) {        throw new IllegalArgumentException("baseUrl must end in /: " + baseUrl);      }      this.baseUrl = baseUrl;      return this;    }    public Retrofit build() {      if (baseUrl == null) {// 必须设置baseUrl, 从上面设置baseUrl可以看出baseUrl不能为null及不包含"/"的url,若不用baseUrl可以设置为"/"        throw new IllegalStateException("Base URL required.");      }      okhttp3.Call.Factory callFactory = this.callFactory;// 执行请求的工厂类,默认为okhttp      if (callFactory == null) {        callFactory = new OkHttpClient();      }      Executor callbackExecutor = this.callbackExecutor;// 请求执行完后, 回调执行器, android默认把请求结果发送到ui线程      if (callbackExecutor == null) {        callbackExecutor = platform.defaultCallbackExecutor();      }      // Make a defensive copy of the adapters and add the default Call adapter.      List<CallAdapter.Factory> adapterFactories = new ArrayList<>(this.adapterFactories);// 转变请求的适配器工厂      adapterFactories.add(platform.defaultCallAdapterFactory(callbackExecutor));      // Make a defensive copy of the converters.      List<Converter.Factory> converterFactories =          new ArrayList<>(1 + this.converterFactories.size());// 对请求结果及请求参数的转变工厂, 当service方法中参数注解为(@Part, @PartMap, @Body)时要提供转换工厂重写请求转换      // Add the built-in converter factory first. This prevents overriding its behavior but also      // ensures correct behavior when using converters that consume all types.      converterFactories.add(new BuiltInConverters());      converterFactories.addAll(this.converterFactories);    // validateEagerly 提前缓存service方法, 不用到请求时再去解析service方法      return new Retrofit(callFactory, baseUrl, converterFactories, adapterFactories,          callbackExecutor, validateEagerly);    }

2.创建service代理

    public <T> T create(final Class<T> service) {        Utils.validateServiceInterface(service);        if (validateEagerly) {//提前缓存service方法          eagerlyValidateMethods(service);        }        return (T) Proxy.newProxyInstance(service.getClassLoader(), new Class<?>[] { service },            new InvocationHandler() {              private final Platform platform = Platform.get();              @Override public Object invoke(Object proxy, Method method, @Nullable Object[] args)                  throws Throwable {                // If the method is a method from Object then defer to normal invocation.                if (method.getDeclaringClass() == Object.class) {// 这个没看懂有什么用                  return method.invoke(this, args);                }                if (platform.isDefaultMethod(method)) {// java8 接口默认方法，直接执行                  return platform.invokeDefaultMethod(method, service, proxy, args);                }                ServiceMethod<Object, Object> serviceMethod =                    (ServiceMethod<Object, Object>) loadServiceMethod(method);// 解析缓存service方法                OkHttpCall<Object> okHttpCall = new OkHttpCall<>(serviceMethod, args);                return serviceMethod.callAdapter.adapt(okHttpCall);// call适配器开始转变call, 若没有提供converterFactories, service方法只能返回Call<ResponseBody> Call<Void>类型              }            });    }    final class BuiltInConverters extends Converter.Factory {// 默认数据转换器      @Override      public Converter<ResponseBody, ?> responseBodyConverter(Type type, Annotation[] annotations,          Retrofit retrofit) {        if (type == ResponseBody.class) {// service方法只能返回Call<ResponseBody> Call<Void>类型          return Utils.isAnnotationPresent(annotations, Streaming.class)              ? StreamingResponseBodyConverter.INSTANCE              : BufferingResponseBodyConverter.INSTANCE;        }        if (type == Void.class) {          return VoidResponseBodyConverter.INSTANCE;        }        return null;        }        ...    }    final class DefaultCallAdapterFactory extends CallAdapter.Factory {// 默认call适配器 android平台默认为ExecutorCallAdapterFactory      static final CallAdapter.Factory INSTANCE = new DefaultCallAdapterFactory();      @Override      public CallAdapter<?, ?> get(Type returnType, Annotation[] annotations, Retrofit retrofit) {        if (getRawType(returnType) != Call.class) {// service方法只能返回Call类型          return null;        }        ...    }OkHttpCall:    // 调用Retrofit的Call的execute()执行下面方法,     private okhttp3.Call createRawCall() throws IOException {        Request request = serviceMethod.toRequest(args);// 把service方法转成okhttp请求参数        okhttp3.Call call = serviceMethod.callFactory.newCall(request);// 通过设置的okhttpclient创建一个okhttp call, 前面所说的Call都为Retrofit的Call类        if (call == null) {          throw new NullPointerException("Call.Factory returned null.");        }        return call;  }

3.loadServiceMethod原理探究

    // 方法注解    Annotation[] methodAnnotations = mMethod.getAnnotations();    // 方法参数类型    Type[] types = mMethod.getGenericParameterTypes();    // 方法参数注解    Annotation[][] parameterAnnotationsArray = mMethod.getParameterAnnotations();   for(int i = 0; i < types.length; i++)    {        Annotation[] parameterAnnotations = parameterAnnotationsArray[i];        for(Annotation annotation : parameterAnnotations)        {           annotation.value();// 注解值        }    }    原理就如上面代码所示, retrofit对获取到注解信息做了很多处理ParameterHandler类