Retrofit2源码阅读(版本：com.squareup.retrofit2:retrofit:2.3.0)
retrofit_stay.png
这个图来自trello，貌似一个叫Stay的大佬做的？感谢大佬。
用一个网络请求的流程来分析阅读，以simples包下的SimpleService为例：
// Create a very simple REST adapter which points the GitHub API.
// https://api.github.com/repos/square/retrofit/contributors
Retrofit retrofit = new Retrofit.Builder()
.baseUrl(API_URL)
.addConverterFactory(GsonConverterFactory.create())
.build();
// Create an instance of our GitHub API interface.
GitHub github = retrofit.create(GitHub.class);
// Create a call instance for looking up Retrofit contributors.
Call> call = github.contributors("square", "retrofit");
// Fetch and print a list of the contributors to the library.
List contributors = call.execute().body();
.....
addConverterFactory方法加入一个Converter工厂，如retrofit2.converter.gson.GsonConverterFactory.
public Builder addConverterFactory(Converter.Factory factory) {
converterFactories.add(checkNotNull(factory, "factory == null"));
return this;
}
retrofit2.Retrofit.Builder#build:
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 adapterFactories = new ArrayList<>(this.adapterFactories);
adapterFactories.add(platform.defaultCallAdapterFactory(callbackExecutor));
// Make a defensive copy of the converters.
List converterFactories = new ArrayList<>(this.converterFactories);
return new Retrofit(callFactory, baseUrl, converterFactories, adapterFactories,
callbackExecutor, validateEagerly);
}
调用retrofit2.Retrofit#create方法生成接口对象。这里用到动态代理：
public T create(final Class 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 serviceMethod =(ServiceMethod) loadServiceMethod(method);
OkHttpCall retrofit2.Retrofit#loadServiceMethod会去serviceMethodCache根据method查找ServiceMethod，如果没有查到，就根据Retrofit对象和method创建一个ServiceMethod（把接口方法的调用适配为一个Http call）。以Method为key，ServiceMethod为value的放入ConcurrentHashMap;
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;
}
retrofit2.ServiceMethod#toRequest:
/** Builds an HTTP request from method arguments. */
Request toRequest(@Nullable Object... args) throws IOException {
RequestBuilder requestBuilder = new RequestBuilder(httpMethod, baseUrl, relativeUrl, headers,
contentType, hasBody, isFormEncoded, isMultipart);
@SuppressWarnings("unchecked") // It is an error to invoke a method with the wrong arg types.
ParameterHandlerretrofit2.OkHttpCall#createRawCall:根据url的参数生成Okhttp3的request ，和call；
private okhttp3.Call createRawCall() throws IOException {
Request request = serviceMethod.toRequest(args);
okhttp3.Call call = serviceMethod.callFactory.newCall(request);
if (call == null) {
throw new NullPointerException("Call.Factory returned null.");
}
return call;
}
okhttp3.RealCall#execute:
@Override public Response execute() throws IOException {
synchronized (this) {
if (executed) throw new IllegalStateException("Already Executed");
executed = true;
}
captureCallStackTrace();
try {
client.dispatcher().executed(this);
Response result = getResponseWithInterceptorChain();
if (result == null) throw new IOException("Canceled");
return result;
} finally {
client.dispatcher().finished(this);
}
}
retrofit2.OkHttpCall#parseResponse,根据T转化为ArrayList
Response parseResponse(okhttp3.Response rawResponse) throws IOException {
ResponseBody rawBody = rawResponse.body();
// Remove the body's source (the only stateful object) so we can pass the response along.
rawResponse = rawResponse.newBuilder()
.body(new NoContentResponseBody(rawBody.contentType(), rawBody.contentLength()))
.build();
int code = rawResponse.code();
if (code < 200 || code >= 300) {
try {
// Buffer the entire body to avoid future I/O.
ResponseBody bufferedBody = Utils.buffer(rawBody);
return Response.error(bufferedBody, rawResponse);
} finally {
rawBody.close();
}
}
if (code == 204 || code == 205) {
rawBody.close();
return Response.success(null, rawResponse);
}
ExceptionCatchingRequestBody catchingBody = new ExceptionCatchingRequestBody(rawBody);
try {
T body = serviceMethod.toResponse(catchingBody);
return Response.success(body, rawResponse);
} catch (RuntimeException e) {
// If the underlying source threw an exception, propagate that rather than indicating it was
// a runtime exception.
catchingBody.throwIfCaught();
throw e;
}
}
retrofit2.ServiceMethod#toResponse:
/** Builds a method return value from an HTTP response body. */
R toResponse(ResponseBody body) throws IOException {
return responseConverter.convert(body);
}
这里因为之前传入的是retrofit2.converter.gson.GsonConverterFactory,由retrofit2.Converter.Factory#responseBodyConverter获得retrofit2.converter.gson.GsonResponseBodyConverter,把ResponseBody 转化为ArrayList