1.Retrofit创建过程
首先 创建一个Retrofit 代码如下:
fun ProvidesRetrofit(okHttpClient: OkHttpClient): Retrofit {
var builder = Retrofit.Builder()
//设置baseUrl
.baseUrl(ApiService.BASE_URL)
//添加一个返回的数据支持转换为Gson对象，其最终会返回配置好的Retrofit类
.addConverterFactory(GsonConverterFactory.create())
//rxjava2的Call进行转化的对象
// .addCallAdapterFactory(RxJava2CallAdapterFactory.create()) //当你使用RxJava的时候要添加这个
//设置OkHttpClient
.client(okHttpClient)
return builder.build()
}
retrofit是通过建造者模式构建出来的。接下来看Builder方法:
public Builder() {
this(Platform.get());
}
查看Platform.get()
private static Platform findPlatform() {
try {
Class.forName("android.os.Build");
if (Build.VERSION.SDK_INT != 0) {
return new Android();
}
} catch (ClassNotFoundException ignored) {
}
try {
Class.forName("java.util.Optional");
return new Java8();
} catch (ClassNotFoundException ignored) {
}
return new Platform();
}
最终调用了findPlatform()方法，根据不同的运行平台提供不用的线程池。
接下来看build方法:
public Retrofit build() {
//baseUrl 必须不为空，否则就包异常了
if (baseUrl == null) {
throw new IllegalStateException("Base URL required.");
}
//this.callFactory是我们构建Retrofit时调用了client方法传进来的
okhttp3.Call.Factory callFactory = this.callFactory;
if (callFactory == null) {
//如果没有设置callFactory则直接创建OkHttpClient
callFactory = new OkHttpClient();
}
//callbackExecutor 用来回调传递到UI线程
Executor callbackExecutor = this.callbackExecutor;
if (callbackExecutor == null) {
callbackExecutor = platform.defaultCallbackExecutor();
}
//adapterFactories 主要用于存储对Call进行转化的对象
List<CallAdapter.Factory> adapterFactories = new ArrayList<>(this.adapterFactories);
adapterFactories.add(platform.defaultCallAdapterFactory(callbackExecutor));
// converterFactories 主要用于存储转化数据对象
List<Converter.Factory> converterFactories = new ArrayList<>(this.converterFactories);
return new Retrofit(callFactory, baseUrl, converterFactories, adapterFactories,
callbackExecutor, validateEagerly);
}
}
client方法 则会调用callFactory方法给this.callFactory 赋值
public Builder client(OkHttpClient client) {
return callFactory(checkNotNull(client, "client == null"));
}
public Builder callFactory(okhttp3.Call.Factory factory) {
//赋值
this.callFactory = checkNotNull(factory, "factory == null");
return this;
}
2.Call的创建过程
下面创建Retrofit实列并调用如下代码来生成接口的动态代理对象:
var apiserver=retrofit.create(ApiService::class.java)
看看retrofit的create方法:
public <T> T create(final Class<T> service) {
Utils.validateServiceInterface(service);
if (validateEagerly) {
eagerlyValidateMethods(service);
}
//返回一个Proxy.newProxyInstance动态代理对象，当我们调用ApiServier的 xxx方法时，最终会调用InvocationHandler的invoke方法
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);
}
//method 是我们定义在ApiServier里面的 xxx方法
ServiceMethod<Object, Object> serviceMethod =
(ServiceMethod<Object, Object>) loadServiceMethod(method);
//这里发起请求
OkHttpCall<Object> okHttpCall = new OkHttpCall<>(serviceMethod, args);
return serviceMethod.callAdapter.adapt(okHttpCall);
}
});
}
loadServiceMethod方法:
private final Map<Method, ServiceMethod<?, ?>> serviceMethodCache = new ConcurrentHashMap<>();
ServiceMethod<?, ?> loadServiceMethod(Method method) {
//读取缓存
ServiceMethod<?, ?> result = serviceMethodCache.get(method);
//如果有缓存 直接返回
if (result != null) return result;
synchronized (serviceMethodCache) {
result = serviceMethodCache.get(method);
if (result == null) {
//没有创建一个，并加入serviceMethodCache缓存
result = new ServiceMethod.Builder<>(this, method).build();
serviceMethodCache.put(method, result);
}
}
return result;
}
再看ServiceMethod怎样构建的:
public ServiceMethod build() {
// 会最终得到们在构建Retrofit调用build方法时 adapterFactories添加对象的get方法 下面给出了说明
callAdapter = createCallAdapter();
//得到的是返回数据的真是类型
responseType = callAdapter.responseType();
if (responseType == Response.class || responseType == okhttp3.Response.class) {
throw methodError("'"
+ Utils.getRawType(responseType).getName()
+ "' is not a valid response body type. Did you mean ResponseBody?");
}
//来遍历converterFactory列表中存储的Converter.Factory,并返回一个合适的Converter用来转换对象
//在构建Retrorfit调用了addConverterFactory(GsonConverterFactory.create())，将GsonConverterFactory（Converter.Factory的子类）添加到converterFactories列表中，表示返回的数据支持转换为JSON对象
responseConverter = createResponseConverter();
for (Annotation annotation : methodAnnotations) {
//方法来对请求方式(比如GET、POST)和请求地址进行过解析 会调用-> parseHttpMethodAndPath()
parseMethodAnnotation(annotation);
}
...
//对方法中的参数注解进行解析 比如（@Query、@Part）
Annotation[] parameterAnnotations = parameterAnnotationsArray[p];
if (parameterAnnotations == null) {
throw parameterError(p, "No Retrofit annotation found.");
}
parameterHandlers[p] = parseParameter(p, parameterType, parameterAnnotations);
}
...
return new ServiceMethod<>(this);
}
ServiceMethod :包含所有网络请求信息的对象
Retrofit的build部分代码:
List<CallAdapter.Factory> adapterFactories = new ArrayList<>(this.adapterFactories);
//adapterFactories 默认会添加defaultCallAdapterFactory。
adapterFactories.add(platform.defaultCallAdapterFactory(callbackExecutor));
defaultCallAdapterFactory指的是ExecutorCallAdapterFactory
CallAdapter.Factory defaultCallAdapterFactory(Executor callbackExecutor) {
if (callbackExecutor != null) {
return new ExecutorCallAdapterFactory(callbackExecutor);
}
return DefaultCallAdapterFactory.INSTANCE;
}
ExecutorCallAdapterFactory的get方法:
@Override
public CallAdapter<?, ?> get(Type returnType, Annotation[] annotations, Retrofit retrofit) {
if (getRawType(returnType) != Call.class) {
return null;
}
final Type responseType = Utils.getCallResponseType(returnType);
//返回CallAdapter对象
return new CallAdapter<Object, Call<?>>() {
@Override public Type responseType() {
//返回数据的真是类型
return responseType;
}
@Override public Call<Object> adapt(Call<Object> call) {
//创建 ExecutorCallbackCall 作用 将call的回调转发至UI线程
return new ExecutorCallbackCall<>(callbackExecutor, call);
}
};
}
responseType 比如 传入Call<xxxBean>,responseType方法就会返回xxxBean。
再看ExecutorCallbackCall方法:
ExecutorCallbackCall(Executor callbackExecutor, Call<T> delegate) {
this.callbackExecutor = callbackExecutor;
this.delegate = delegate;
}
@Override public void enqueue(final Callback<T> callback) {
if (callback == null) throw new NullPointerException("callback == null");
//方法最终调用delegate的enqueue方法。delegate是传入的OkHttpCall
delegate.enqueue(new Callback<T>() {
@Override public void onResponse(Call<T> call, final Response<T> response) {
callbackExecutor.execute(new Runnable() {
@Override public void run() {
if (delegate.isCanceled()) {
// Emulate OkHttp's behavior of throwing/delivering an IOException on cancellation.
callback.onFailure(ExecutorCallbackCall.this, new IOException("Canceled"));
} else {
callback.onResponse(ExecutorCallbackCall.this, response);
}
}
});
}
@Override public void onFailure(Call<T> call, final Throwable t) {
callbackExecutor.execute(new Runnable() {
@Override public void run() {
callback.onFailure(ExecutorCallbackCall.this, t);
}
});
}
});
}
主要是实现了Call接口 和对Call接口的封装，他主要添加了通过Retrofit的callbackExecutor将请求回调到UI线程，Call会调用他的enqueue方法，其实调用的是ExecutorCallbackCall的enqueue
3.Call的enqueue方法
来看OkHttpCall的enqueue
@Override public void enqueue(final Callback<T> callback) {
if (callback == null) throw new NullPointerException("callback == null");
okhttp3.Call call;
Throwable failure;
...
//调用okhttp3的call的enqueue
call.enqueue(new okhttp3.Callback() {
@Override public void onResponse(okhttp3.Call call, okhttp3.Response rawResponse)
throws IOException {
Response<T> response;
try {
response = parseResponse(rawResponse);
} catch (Throwable e) {
callFailure(e);
return;
}
callSuccess(response);
}
@Override public void onFailure(okhttp3.Call call, IOException e) {
try {
callback.onFailure(OkHttpCall.this, e);
} catch (Throwable t) {
t.printStackTrace();
}
}
private void callFailure(Throwable e) {
try {
callback.onFailure(OkHttpCall.this, e);
} catch (Throwable t) {
t.printStackTrace();
}
}
private void callSuccess(Response<T> response) {
try {
callback.onResponse(OkHttpCall.this, response);
} catch (Throwable t) {
t.printStackTrace();
}
}
});
}
parseResponse方法 返回一个response
Response<T> 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 {
//解析数据返回body，在此前例子 我们传入的是GsonConverterFactory
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;
}
}
根据返回的的不同状态吗code来做不同操作，
总结:Call的enqueue方法主要是用于OkHttp来请求网络，将返回的Response进行数据转换并回调给UI线程。
