retrofit源码分析 | 易学教程

最近时间比较空闲，梳理了下retrofit的源码，和大家分享下，估计分析的不是很完善，不喜勿喷

从整体架构上了说，retrofit是对okhttp的进一步封装，底层使用的是okhttp框架，通过动态代理的设计模式和注解，并且和rxjava进行无缝对接，使使用起来更加方便，准确的说retrofit只负责网络请求接口的封装。

1.1 Retrofit的创建

public Retrofit build() {

  if (baseUrl == null) {
    throw new IllegalStateException("Base URL required.");
  }

  okhttp3.Call.Factory callFactory = this.callFactory;
  if (callFactory == null) {
    callFactory = new OkHttpClient();
  }

  Executor callbackExecutor = this.callbackExecutor;
  if (callbackExecutor == null) {
    callbackExecutor = platform.defaultCallbackExecutor();
  }

  // Make a defensive copy of the adapters and add the default Call adapter.
  List<CallAdapter.Factory> callAdapterFactories = new ArrayList<>(this.callAdapterFactories);
  callAdapterFactories.add(platform.defaultCallAdapterFactory(callbackExecutor));

  // Make a defensive copy of the converters.
  List<Converter.Factory> converterFactories =
      new ArrayList<>(1 + this.converterFactories.size());

  // 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);

  return new Retrofit(callFactory, baseUrl, unmodifiableList(converterFactories),
      unmodifiableList(callAdapterFactories), callbackExecutor, validateEagerly);
}

Retrofit(okhttp3.Call.Factory callFactory, HttpUrl baseUrl,
    List<Converter.Factory> converterFactories, List<CallAdapter.Factory> callAdapterFactories,
    @Nullable Executor callbackExecutor, boolean validateEagerly) {
  this.callFactory = callFactory;
  this.baseUrl = baseUrl;
  this.converterFactories = converterFactories; // Copy+unmodifiable at call site.
  this.callAdapterFactories = callAdapterFactories; // Copy+unmodifiable at call site.
  this.callbackExecutor = callbackExecutor;
  this.validateEagerly = validateEagerly;
}

通过源码可以看出Retrofit通过builder的方式进行创建。
baseUrl--  网络请求的URL地址 
callFactory--  生产网络请求器，Retrofit使用的也是Okhttp的网络请求，只是对Okhttp进行了封装
converterFactories -- 数据工厂转换器类，主要是对数据进行转换
callAdapterFactories -- 网络请求适配器工厂
callbackExecutor -- 回调方法执行器

比如 -- .addCallAdapterFactory(RxJavaCallAdapterFactory.create()) .addConverterFactory(GsonConverterFactory.create());可以和RXJava进行无缝对接

1.2 最重要的一步就是进行网络请求

public <T> T create(final Class<T> service) {
  Utils.validateServiceInterface(service);
  if (validateEagerly) {
    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) {
            return method.invoke(this, args);
          }
          if (platform.isDefaultMethod(method)) {
            return platform.invokeDefaultMethod(method, service, proxy, args);
          }
          ServiceMethod<Object, Object> serviceMethod =
              (ServiceMethod<Object, Object>) loadServiceMethod(method);
          OkHttpCall<Object> okHttpCall = new OkHttpCall<>(serviceMethod, args);
          return serviceMethod.adapt(okHttpCall);
        }
      });
}

下面这三行是最重要的部分，retrofit通过动态代理的设计方式将Okhttp进行了封装，而真正的请求是通过Okhttp进行的

ServiceMethod<Object, Object> serviceMethod = (ServiceMethod<Object, Object>) loadServiceMethod(method);

//Retroit的请求主要是通过一个接口进行的，比如

@PUT("platform/client/password/resetPassword")

Call<BaseResponse> forgetPassword(@Body ForgetPasswordRequest request);

serviceMethod的作用就是将接口里面的注解进行解析，得到请求的方式，请求的URL地址等一系列请求的条件

OkHttpCall<Object> okHttpCall = new OkHttpCall<>(serviceMethod, args);

//这一步的作用是构建一个真正的请求对象，Retrofit的所有的请求都是通过OklhttpCall进行实现的。

return serviceMethod.adapt(okHttpCall);

//通过这一步返回一个OkhttpCall进行代理包装

来源：CSDN

作者：qq_36190583

链接：https://blog.csdn.net/qq_36190583/article/details/103850652

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