Retrofit2是一个网络框架，基于OkHttp3框架封装的网络框架。
大致理解，实现一个Api对应的接口，调用Retrofit.create 方法，通过动态代理模式生成对应的代理service，并加入okhttp的请求队列中，之后可以调用对应的方法进行请求。
创建service的方式：如果想调用同步的请求，只需调用execute方法，而enqueue则会调用一个异步请求。
优点：1.降低耦合度，api之间互不干扰 2.代码风格：使用注解方式，代码简洁（相同的还有ButterKnife，以及degger，EventBus等框架同样是使用注解） 3.采用构建者模式以及动态代理模式，更灵活
Retrofit2使用流程
1初始化Retrofit(构建者模式)
Retrofit singleton； //拦截 用于输出LOG 将请求以及返回值以log形式打印出来
HttpLoggingInterceptor interceptor = new HttpLoggingInterceptor(new HttpLoggingInterceptor.Logger() {
@Override
public void log(String message) {
Log.i("tag", "log: ========" + message);
}
}).setLevel(HttpLoggingInterceptor.Level.BODY);
HttpLoggingInterceptor interceptor =new HttpLoggingInterceptor(new HttpLoggingInterceptor.Logger() {
@Override
public void log(String message) {
Log.i("tag", "log: ========" + message);
}
}).setLevel(HttpLoggingInterceptor.Level.BODY);
//将拦截器add给OkhttpClient 在不设置OkHttpclient的情况下 retrofit会使用默认的client
OkHttpClient okHttpClient = new OkHttpClient.Builder()
.writeTimeout(10, TimeUnit.SECONDS)
.addInterceptor(interceptor)
.build();
singleton = new Retrofit.Builder()
.baseUrl(host)
.addCallAdapterFactory(RxJava2CallAdapterFactory.create())//支持rxandroid使用的 需要依赖另外的框架
.addConverterFactory(GsonConverterFactory.create())//支持gson解析使用的 需要依赖另外的框架 compile 'com.squareup.retrofit2:converter-gson:2.2.0'
.client(okHttpClient)
.build();2.创建对应的api接口public interface NewsApiService {
/**
* 参数过多
*/
@GET("users/stven0king/repos")
Call<String> getNewsByMap(@QueryMap Map<String, String> params);
}详细的注解使用方式 http://blog.csdn.net/xiangjai/article/details/51452217http://www.open-open.com/lib/view/open1453552147323.html3.api进行请求NewsApiService newsApiService = retrofit.create(NewsApiService.class);Map<String,String> map=new HashMap<>();
map.put("a","a");
//get 参数map
Call<String> newsByMap = newsApiService.getNewsByMap(map);
newsByMap.enqueue(new Callback<String>() {
@Override
public void onResponse(Call<String> call, Response<String> response) {
}
@Override
public void onFailure(Call<String> call, Throwable t) {
}
});每次生成的api对应的call只能使用一次，支持取消等方法 如果想调用同步的请求，只需调用execute方法，而enqueue则会调用一个异步请求二：部分源码解析
1.动态代理模式 动态生成对应的代理类，更灵活简便(反射的原理) 并且可以在执行委托类方法时，统一增加另外的处理代码
public interface TestInterface {
void get();
void post();
}public class CustomHandler implements InvocationHandler{
private TestInterface obj;
public CustomHandler(TestInterface obj) {
this.obj = obj;
}
@Override
public Object invoke(Object o, Method method, Object[] objects) throws Throwable {
Log.d("tag", "invoke() called with: o = [" + o + "], method = [" + method + "], objects = [" + objects + "]");
return method.invoke(this.obj,objects);
}
}TestInterface realSub=new RealSub();
CustomHandler handler=new CustomHandler(realSub);
TestInterface proxyInstance = (TestInterface) Proxy.newProxyInstance(realSub.getClass().getClassLoader(), realSub.getClass().getInterfaces(), handler);
proxyInstance.get();
proxyInstance.post();
Retrofit2中的源码public <T> T create(final Class<T> service) {
Utils.validateServiceInterface(service);//检查接口是否符合规则
if (validateEagerly) {
eagerlyValidateMethods(service);//检查接口是否符合规则
}
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, 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);
} //从缓存中取出调用的方法，并生成对应的okhttp的请求,调用请求方法的时候，返回请求结果
ServiceMethod<Object, Object> serviceMethod =
(ServiceMethod<Object, Object>) loadServiceMethod(method);
OkHttpCall<Object> okHttpCall = new OkHttpCall<>(serviceMethod, args);
return serviceMethod.callAdapter.adapt(okHttpCall); }
});
}private void eagerlyValidateMethods(Class<?> service) {
Platform platform = Platform.get();
for (Method method : service.getDeclaredMethods()) {
if (!platform.isDefaultMethod(method)) {
loadServiceMethod(method);
}
}
}
//将加载的类中的方法加入map的缓存中。
ServiceMethod<?, ?> loadServiceMethod(Method method) {
ServiceMethod<?, ?> result = serviceMethodCache.get(method);
if (result != null) return result;
synchronized (serviceMethodCache) {
result = serviceMethodCache.get(method);
if (result == null) {
result = new ServiceMethod.Builder<>(this, method).build();
serviceMethodCache.put(method, result);
}
}
return result;
}
