简单实现Retrofit（替代Okhttp）

1.定义注解参数

@Documented
@Target(PARAMETER)
@Retention(RUNTIME)
public @interface Field {String value();
}
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@Documented
@Target(METHOD)
@Retention(RUNTIME)
public @interface Get {String value() default "";
}
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@Documented
@Target(METHOD)
@Retention(RUNTIME)
public @interface Post {String value() default "";
}
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2.实现回调接口Call和Callback MyCall .class

public interface MyCall {//执行网络请求（同步：在当前网络）String execute() throws Exception;//在子线程请求网络void enqueue(MyCallback callback);
}
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MyCallback .class

/*** 网络请求回调接口*/
public interface MyCallback {void onResponse( String response);void onFailure( Exception e);
}
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SystemHttpCall .class

/*** Created by Xionghu on 2017/8/14.* Desc: 具体的实现类发送请求*/public class SystemHttpCall implements MyCall {private MyServiceMethod serviceMethod;public SystemHttpCall(MyServiceMethod serviceMethod) {this.serviceMethod = serviceMethod;}@Overridepublic String execute() throws Exception {if (serviceMethod.isPost()) {return HttpUtils.post(serviceMethod.baseUrl(), serviceMethod.getParam());} else {return HttpUtils.get(serviceMethod.baseUrl());}}@Overridepublic void enqueue(MyCallback callback) {HttpTask httpTask = new HttpTask(this, callback);httpTask.execute();}public class HttpTask extends AsyncTask<Void, Void, String> {private SystemHttpCall httpCall;private MyCallback callback;private HttpTask(SystemHttpCall httpCall, MyCallback callback) {this.httpCall = httpCall;this.callback = callback;}@Overrideprotected String doInBackground(Void... params) {try {return httpCall.execute();} catch (Exception e) {e.printStackTrace();}return null;}@Overrideprotected void onPostExecute(String result) {if (this.callback != null) {if (result != null) {this.callback.onResponse(result);} else {this.callback.onFailure(new Exception("网络异常！"));}}}}
}
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3.解析注解方法获取相应参数

public class MyServiceMethod {private Builder builder;public MyServiceMethod(Builder builder) {this.builder = builder;}public boolean isPost() {return this.builder.isPost;}public Map<String, Object> getParam() {return this.builder.paramMap;}public String baseUrl() {StringBuffer buffer = new StringBuffer(this.builder.retrofit.getBaseUrl() + this.builder.relativeUrl);if (!isPost()) {// 如果你不是Post请求，是get请求，需要拼接参数地址if (this.builder.paramMap != null) {Set<String> keySet = this.builder.paramMap.keySet();if (keySet.size() > 0) {buffer.append("?");}for (String key : keySet) {Object value = this.builder.paramMap.get(key);buffer.append(key);buffer.append("=");buffer.append(value);buffer.append("&");}buffer.deleteCharAt(buffer.length() - 1);}}return buffer.toString();}static final class Builder {final MyRetrofit retrofit;final Method method;final Annotation[] methodAnnotations;final Annotation[][] parameterAnnotationsArray;String relativeUrl;// 参数集合Map<String, Object> paramMap;Object[] args;boolean isPost;public Builder(MyRetrofit retrofit, Method method, Object[] args) {this.retrofit = retrofit;this.method = method;// 方法注解列表(相当于我们的LoginService中的: @POST和@FormUrlEncoded......)this.methodAnnotations = method.getAnnotations();// 方法参数注解列表(相当于我们的LoginService中的: @Field......)this.parameterAnnotationsArray = method.getParameterAnnotations();this.args = args;this.paramMap = new HashMap<String, Object>();}public MyServiceMethod build() {// 循环遍历方法注解列表for (Annotation annotation : methodAnnotations) {parseMethodAnnotation(annotation);}int parameterCount = parameterAnnotationsArray.length;for (int p = 0; p < parameterCount; p++) {Annotation[] parameterAnnotations = parameterAnnotationsArray[p];parseParameterAnnotation(p, parameterAnnotations);}return new MyServiceMethod(this);}/*** 解析方法注解** @param annotation*/public void parseMethodAnnotation(Annotation annotation) {// 首先判断注解类型(解析目的：获取接口名称,用于拼接地址)if (annotation instanceof Get) {this.relativeUrl = ((Get) annotation).value();isPost = false;} else if (annotation instanceof Post) {this.relativeUrl = ((Post) annotation).value();isPost = true;}}/*** 解析参数注解** @param p* @param parameterAnnotations*/private void parseParameterAnnotation(int p,Annotation[] parameterAnnotations) {// 方法参数值Object value = args[p];// 遍历方法参数注解for (Annotation annotation : parameterAnnotations) {// 首先需要判断该注解的类型if (annotation instanceof Field) {Field field = (Field) annotation;// 参数的名称(接口参数名称，服务器接口规定的)String key = field.value();paramMap.put(key, value);}}}}
}
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4.定义MyRetrofit框架

public class MyRetrofit {// 缓存方法(为了避免重复加载方法注解，从而耗费性能)private final Map<Method, MyServiceMethod> serviceMethodCache = new LinkedHashMap<Method, MyServiceMethod>();public String getBaseUrl() {return baseUrl;}public void setBaseUrl(String baseUrl) {this.baseUrl = baseUrl;}private String baseUrl;private MyRetrofit(String baseUrl){this.baseUrl = baseUrl;}public <T> T create(Class<T> service){//动态代理实现return (T) Proxy.newProxyInstance(service.getClassLoader(), new Class<?>[]{service}, new InvocationHandler() {@Overridepublic Object invoke(Object proxy, Method method, Object[] args) throws Throwable {MyServiceMethod serviceMethod = loadServiceMethod(method, args);SystemHttpCall httpCall = new SystemHttpCall(serviceMethod);return httpCall;}});}// 第一步：解析方法（说白了解析方法注解和方法参数注解）// 第二步：实现网络请求protected MyServiceMethod loadServiceMethod(Method method, Object[] args) {MyServiceMethod result;synchronized (serviceMethodCache) {result = serviceMethodCache.get(method);if (result == null) {result = new MyServiceMethod.Builder(this, method, args).build();serviceMethodCache.put(method, result);}}return result;}public static final class Builder{private String baseUrl;public Builder baseUrl(String baseUrl){this.baseUrl = baseUrl;return this;}public MyRetrofit build(){if(baseUrl == null){throw new IllegalStateException("Base URL required.");}return new MyRetrofit(baseUrl);}}}
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5.具体实现网络请求类 定义接口方法类

public interface MyRetrofitLoginService {
@Post("user/login?platform=android&city_id=101&type=pwd&channel=baiduxi&version=3.2.0&os_version=6.0.1&device_id=866622020797175")MyCall login(@Field("mobile") String name, @Field("password") String pwd);
}
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简单封装请求工具类

public class MyRetrofitTest {private static String URL_SERVER = "http://api.cloud.test.haocaisong.cn/v2.0/";public static void login(String name, String pwd, final SimpleSystemLogin.OnHttpResultListener onHttpResultListener) {MyRetrofit myRetrofit = new MyRetrofit.Builder().baseUrl(URL_SERVER).build();MyRetrofitLoginService loginService = myRetrofit.create(MyRetrofitLoginService.class);MyCall myCall = loginService.login(name,pwd);myCall.enqueue(new MyCallback() {@Overridepublic void onResponse(String response) {onHttpResultListener.onHttpResult(response);}@Overridepublic void onFailure(Exception e) {}});}
}
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