反射+注解+retrofit+okhttp3总结

一键归纳okhttp3&＃43;retrofit2架构&＃xff0c;反射&＃43;注解&＃43;retrofit手写框架

下面两篇文章是我觉得理解比较透彻和详细的文章

一、首先你需要了解什么是动态代理

Retrofit源码学习之动态代理

二、其次你要了解一下retrofit2的基本使用以及源码解析

Retrofit 是一个 RESTful 的 HTTP 网络请求框架的封装&＃xff0c;网络请求的工作本质上是 OkHttp 完成&＃xff0c;而 Retrofit 仅负责网络请求接口的封装。

从架构角度看Retrofit的作用、原理和启示

三、简单的利用注解反射实现retrofit网络请求&＃xff0c;有助于理解其中的基本原理

此处仅为基本使用&＃xff0c;适配器和转换器未使用。距离完整的框架还差一大截

下面开始看代码

元数据

public interface WeatherApi {&＃64;POST("/v3/weather/weatherInfo")&＃64;FormUrlEncodedCall postWeather(&＃64;Field("city") String city, &＃64;Field("key") String key);&＃64;GET("/v3/weather/weatherInfo")Call getWeather(&＃64;Query("city") String city, &＃64;Query("key") String key);
}

看一下自定义的注解&＃xff0c;用于方法注解&＃xff0c;适用于运行期

&＃64;Target(METHOD)
&＃64;Retention(RUNTIME)
public &＃64;interface GET {String value() default "";
}

&＃64;Target(METHOD)
&＃64;Retention(RUNTIME)
public &＃64;interface POST {String value() default "";
}

自定义的retrofit

public class MyRetrofit {final Map serviceMethodCache &＃61; new ConcurrentHashMap<>();final Call.Factory callFactory;final HttpUrl baseUrl;MyRetrofit(Call.Factory callFactory, HttpUrl baseUrl) {this.callFactory &＃61; callFactory;this.baseUrl &＃61; baseUrl;}public T create(final Class service) {return (T) Proxy.newProxyInstance(service.getClassLoader(), new Class[]{service},new InvocationHandler() {&＃64;Overridepublic Object invoke(Object proxy, Method method, Object[] args) throws Throwable {//解析这个method 上所有的注解信息ServiceMethod serviceMethod &＃61; loadServiceMethod(method);//args:return serviceMethod.invoke(args);}});}private ServiceMethod loadServiceMethod(Method method) {//先不上锁&＃xff0c;避免synchronized的性能损失ServiceMethod result &＃61; serviceMethodCache.get(method);if (result !&＃61; null) return result;//多线程下&＃xff0c;避免重复解析,synchronized (serviceMethodCache) {result &＃61; serviceMethodCache.get(method);if (result &＃61;&＃61; null) {result &＃61; new ServiceMethod.Builder(this, method).build();serviceMethodCache.put(method, result);}}return result;}/*** 构建者模式&＃xff0c;将一个复杂对象的构建和它的表示分离&＃xff0c;可以使使用者不必知道内部组成的细节。*/public static final class Builder {private HttpUrl baseUrl;//Okhttp->OkhttClientprivate okhttp3.Call.Factory callFactory; //nullpublic Builder callFactory(okhttp3.Call.Factory factory) {this.callFactory &＃61; factory;return this;}public Builder baseUrl(String baseUrl) {this.baseUrl &＃61; HttpUrl.get(baseUrl);return this;}public MyRetrofit build() {if (baseUrl &＃61;&＃61; null) {throw new IllegalStateException("Base URL required.");}okhttp3.Call.Factory callFactory &＃61; this.callFactory;if (callFactory &＃61;&＃61; null) {callFactory &＃61; new OkHttpClient();}return new MyRetrofit(callFactory, baseUrl);}}
}

接下来是ServiceMethod 记录请求类型 参数 完整地址

public class ServiceMethod {private final Call.Factory callFactory;private final String relativeUrl;private final boolean hasBody;private final ParameterHandler[] parameterHandler;private FormBody.Builder formBuild;HttpUrl baseUrl;String httpMethod;HttpUrl.Builder urlBuilder;public ServiceMethod(Builder builder) {//获取代理对象myretrofit的参数&＃xff0c;以便封装请求参数baseUrl &＃61; builder.enjoyRetrofit.baseUrl;callFactory &＃61; builder.enjoyRetrofit.callFactory;httpMethod &＃61; builder.httpMethod;relativeUrl &＃61; builder.relativeUrl;hasBody &＃61; builder.hasBody;parameterHandler &＃61; builder.parameterHandler;//如果是有请求体,创建一个okhttp的请求体对象if (hasBody) {formBuild &＃61; new FormBody.Builder();}}public Object invoke(Object[] args) {/*** 1 处理请求的地址与参数* 这里也是在invoke里要实现的网络请求*/for (int i &＃61; 0; i }


public abstract class ParameterHandler {abstract void apply(ServiceMethod serviceMethod, String value);static class QueryParameterHandler extends ParameterHandler {String key;public QueryParameterHandler(String key) {this.key &＃61; key;}//serviceMethod: 回调&＃64;Overridevoid apply(ServiceMethod serviceMethod, String value) {serviceMethod.addQueryParameter(key,value);}}static class FiledParameterHandler extends ParameterHandler {String key;public FiledParameterHandler(String key) {this.key &＃61; key;}&＃64;Overridevoid apply(ServiceMethod serviceMethod, String value) {serviceMethod.addFiledParameter(key,value);}}
}

最后调用、点击事件卸在view里。不展示了

public class MainActivity extends AppCompatActivity {private static final String TAG &＃61; "MainActivity";private EnjoyWeatherApi enjoyWeatherApi;&＃64;Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);MyRetrofit enjoyRetrofit &＃61; new MyRetrofit.Builder().baseUrl("https://restapi.amap.com").build();enjoyWeatherApi &＃61; enjoyRetrofit.create(EnjoyWeatherApi.class);}public void enjoyPost(View view) {okhttp3.Call call &＃61; enjoyWeatherApi.postWeather("110101", "ae6c53e2186f33bbf240a12d80672d1b");call.enqueue(new okhttp3.Callback() {&＃64;Overridepublic void onFailure(okhttp3.Call call, IOException e) {}&＃64;Overridepublic void onResponse(okhttp3.Call call, okhttp3.Response response) throws IOException {Log.i(TAG, "onResponse enjoy post: " &＃43; response.body().string());response.close();}});}
}