retrofit2+rxjava+mockserver使用和理解
特点概要
Square的retrofit作为目前android比较火的网络框架，具有以下特点：
1、rest api 风格
2、网络核心使用优秀开源框架okttp，其本身致力于组装request和便捷转换response。
3、代码简洁，拓展性高，开发包只有90k左右
4、支持RxJava、Guava、Java8等适配器。
简单使用
案例是一个简单的登陆请求案例。使用name和pwd参数登陆接口，返回获取response并直接转换成User对象，User有两个成员变量name，age。
使用步骤分解为：
1、创建retrofit
private void initRetrofit(){
retrofit = new Retrofit.Builder()
.baseUrl("http://192.168.56.1:12306/")
.addConverterFactory(GsonConverterFactory.create())
.build();
}2、定义接口
public interface ApiServicce {
@FormUrlEncoded
@POST("/user/login/")
Call login(@Field("name")String name, @Field("pwd")String pwd);
}
3、创建Call代理对象
ApiServicce apiService = retrofit.create(ApiServicce.class);
Call userCall = apiService.login("name","retrofit"); 4、发起请求并获取回调内容
@Override
public void onResponse(Call call, Response response) {
User user = response.body();
}
@Override
public void onFailure(Call call, Throwable t) {
System.err.println(call.toString());
}
}); 以上四个步骤就完成了一个完成的数据请求和回复的解析。高度解耦的特点只能用简洁优雅来形容。那么他怎么做到的呢我们稍后分析。这里涉及到一个的接口是使用mockserver来模拟完成的，有关于mockserver的工作可以从github mockserver了解。这里我使用的是简易的moco，只需要是简单使用其jar包和定义一个配置便可以轻松的完成一次模拟过程。详情可以参考这里。
服务启动命令：
java -jar moco-runner-0.11.0-standalone.jar http -p 12306 -c foo.json
foo.json内容：
[
{
"request" :
{
"uri" :"/user/login/",
"method" :"post"
},
"response" :
{
"json" :
{
"name" : "jerry",
"age" :"24"
}
}
},
{
"request":
{
"uri" : "/"
},
"response" :
{
"text" : "hello"
}
}
]
可以看出调用
http://192.168.56.1:12306/返回hello的文本内容，调用http://192.168.56.1:12306/user/login 返回上述的json串再经由retrofit转换成对应的java对象。ok，大体了解了使用方法，开始剖析他的工作原理。
原理剖析
可以看出其工作流程主要分为下面四步
下面对其源码进行分析：
结合我们使用过程 retrofit build
retrofit 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);
} 实例CallFactory，CallFactory决定调用的网络模块使用的是哪个,这里默认使用的是OkHttpClient。成员callbackExecutor为执行回调的任务或线程。成员adapterFactories存放CallAdapter的一个列表，并且add一个默认的AdapterFactory,AdapterFactory中get方法用来获取到指定的CallAdapter。先来看下默认的AdapterFactory是什么，位置ExecutorCallAdapterFactory类。
CallAdapter
@Override
public CallAdapter> get(Type returnType, Annotation[] annotations, Retrofit retrofit) {
if (getRawType(returnType) != Call.class) {
return null;
}
final Type responseType = Utils.getCallResponseType(returnType);
return new CallAdapter>() {
@Override public Type responseType() {
return responseType;
}
@Override public Call adapt(Call call) {
return new ExecutorCallbackCall<>(callbackExecutor, call);
}
};
} return new ExecutorCallbackCall，那么看下这个ExecutorCallbackCall是什么
static final class ExecutorCallbackCall implements Call {
final Executor callbackExecutor;
final Call delegate;
ExecutorCallbackCall(Executor callbackExecutor, Call delegate) {
this.callbackExecutor = callbackExecutor;
this.delegate = delegate;
}
@Override public void enqueue(final Callback callback) {
if (callback == null) throw new NullPointerException("callback == null");
delegate.enqueue(new Callback() {
@Override public void onResponse(Call call, final Response 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 call, final Throwable t) {
callbackExecutor.execute(new Runnable() {
@Override public void run() {
callback.onFailure(ExecutorCallbackCall.this, t);
}
});
}
});
}
@Override public boolean isExecuted() {
return delegate.isExecuted();
}
@Override public Response execute() throws IOException {
return delegate.execute();
}
@Override public void cancel() {
delegate.cancel();
}
@Override public boolean isCanceled() {
return delegate.isCanceled();
}
@SuppressWarnings("CloneDoesntCallSuperClone") // Performing deep clone.
@Override public Call clone() {
return new ExecutorCallbackCall<>(callbackExecutor, delegate.clone());
}
@Override public Request request() {
return delegate.request();
}
} ok，很简单。只是一个Call的代理类,不了解Call对象的可以去研究下okhttp。delegate.enqueue回复之后使用callbackExecutor将回复处理放回到一个子线程交由callback处理。做好这些准备工作之后。需要看下他是如果做到create代理对象的解耦和连接整个的工作流程。
retrofit create
retrofit.create(申明的接口class)
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, 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 = loadServiceMethod(method);
OkHttpCall okHttpCall = new OkHttpCall<>(serviceMethod, args);
return serviceMethod.callAdapter.adapt(okHttpCall);
}
});
} 可以看出这里使用了一个动态代理来代理service类，观察其InvocationHandler代理改变的部分，其Object的方法都自动被原样的执行，当调用service里面的请求方法的时候会被Proxy拦截，loadServiceMethod方法讲原方法包装成ServiceMethod,ServiceMethod类主要工作是解析注解、传参，将他们分装成request，然后再根据具体的返回值，将之前配置的工场Factory生成具体的CallAdapter和ResponseConvert。 OkHttpCall okHttpCall = new OkHttpCall<>(serviceMethod, args)。显式的实例了一个OkhttpCall对象,OkHttpCall封装了Call(okhttp中的对象)，说明retrofit是使用了okttp最为网络的核心模块。最后一步serviceMethod.callAdapter.adapt(okHttpCall)，callAdater是用来做什么的呢，其本质是将call转成一个T型的策略。下面先对CallAdapter如何工作的进行剖析，并且如何整合Rxjava来使用的。
结合Rxjava
如果我们想使用Rxjava 那么接口方法定义得是这样的
@FormUrlEncoded
@POST
Observable rxLogin(@Field("name")String name, @Field("pwd")String pwd); 那么如何才能转换成我们想要的Observable类型呢，前面我们说过CallAdapter旨在转换Call成为我们想要的T类型。那么需要在CallAdapter上做文章了。重点看下RxJavaCallAdapterFactory类
public final class RxJavaCallAdapterFactory implements CallAdapter.FactoryCallAdapter.Factory是Retrofit这个库中的接口，用来给我们自定义去解析我们自己想要的类型用的。
get方法获取CallAdapter的方法
@Override
public CallAdapter get(Type returnType, Annotation[] annotations, Retrofit retrofit) {
Class rawType = Utils.getRawType(returnType);
boolean isSingle = "rx.Single".equals(rawType.getCanonicalName());
if (rawType != Observable.class && !isSingle) {
return null;
}
if (!(returnType instanceof ParameterizedType)) {
String name = isSingle ? "Single" : "Observable";
throw new IllegalStateException(name + " return type must be parameterized"
+ " as " + name + " or " + name + "");
}
CallAdapter> callAdapter = getCallAdapter(returnType);
if (isSingle) {
// Add Single-converter wrapper from a separate class. This defers classloading such that
// regular Observable operation can be leveraged without relying on this unstable RxJava API.
return SingleHelper.makeSingle(callAdapter);
}
return callAdapter;
} 如果不是Observable的类型，则不去处理.Observable类型则调用callAdapter（）方法获取对应的CallAdapter。callAdapter()方法中return SimpleCallAdapter的实例，那么观察SimpleCallAdapter的实现
static final class SimpleCallAdapter implements CallAdapter> {
private final Type responseType;
private final Scheduler scheduler;
SimpleCallAdapter(Type responseType, Scheduler scheduler) {
this.responseType = responseType;
this.scheduler = scheduler;
}
@Override public Type responseType() {
return responseType;
}
@Override public Observable adapt(Call call) {
Observable observable = Observable.create(new CallOnSubscribe<>(call)) //
.lift(OperatorMapResponseToBodyOrError.instance());
if (scheduler != null) {
return observable.subscribeOn(scheduler);
}
return observable;
}
} 好了，最终我们看到了adapter返回类型就是Observeble了。再回顾下retrofit create的过程中我们代理proxy return的结果是serviceMethod.callAdapter.apater(call)那么我们取得的是不是就一个Observerble对象了！！！那么create拿到的代理对象就是一个observable对象。就可以轻松的使用Rxjava了！！！如果不了解rxjava的可以了解下github rxjava
Request and Response
retrofit的重点是是组装request和回复response类型的转换。serviceMethod类是用来根据注解组装请求参数的。serviceMethod的build方法
public ServiceMethod build() {
callAdapter = createCallAdapter();
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?");
}
responseConverter = createResponseConverter();
for (Annotation annotation : methodAnnotations) {
parseMethodAnnotation(annotation);
}
if (httpMethod == null) {
throw methodError("HTTP method annotation is required (e.g., @GET, @POST, etc.).");
}
if (!hasBody) {
if (isMultipart) {
throw methodError(
"Multipart can only be specified on HTTP methods with request body (e.g., @POST).");
}
if (isFormEncoded) {
throw methodError("FormUrlEncoded can only be specified on HTTP methods with "
+ "request body (e.g., @POST).");
}
}
int parameterCount = parameterAnnotationsArray.length;
parameterHandlers = new ParameterHandler[parameterCount];
for (int p = 0; p < parameterCount; p++) {
Type parameterType = parameterTypes[p];
if (Utils.hasUnresolvableType(parameterType)) {
throw parameterError(p, "Parameter type must not include a type variable or wildcard: %s",
parameterType);
}
Annotation[] parameterAnnotations = parameterAnnotationsArray[p];
if (parameterAnnotations == null) {
throw parameterError(p, "No Retrofit annotation found.");
}
parameterHandlers[p] = parseParameter(p, parameterType, parameterAnnotations);
}
if (relativeUrl == null && !gotUrl) {
throw methodError("Missing either @%s URL or @Url parameter.", httpMethod);
}
if (!isFormEncoded && !isMultipart && !hasBody && gotBody) {
throw methodError("Non-body HTTP method cannot contain @Body.");
}
if (isFormEncoded && !gotField) {
throw methodError("Form-encoded method must contain at least one @Field.");
}
if (isMultipart && !gotPart) {
throw methodError("Multipart method must contain at least one @Part.");
}
return new ServiceMethod<>(this);
}createCallAdapter创建对应的callAdapter，即从CallAdapterFactory中取出需要的适配器，responseConverter创建对应的回复处理类，从List
@Override public void enqueue(final Callback callback) {
if (callback == null) throw new NullPointerException("callback == null");
okhttp3.Call call;
Throwable failure;
synchronized (this) {
if (executed) throw new IllegalStateException("Already executed.");
executed = true;
call = rawCall;
failure = creationFailure;
if (call == null && failure == null) {
try {
call = rawCall = createRawCall();
} catch (Throwable t) {
failure = creationFailure = t;
}
}
}
if (failure != null) {
callback.onFailure(this, failure);
return;
}
if (canceled) {
call.cancel();
}
call.enqueue(new okhttp3.Callback() {
@Override public void onResponse(okhttp3.Call call, okhttp3.Response rawResponse)
throws IOException {
Response 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 response) {
try {
callback.onResponse(OkHttpCall.this, response);
} catch (Throwable t) {
t.printStackTrace();
}
}
});
} 使用okttp的call对象拿到回复之后调用parseResponse获得到指定的response对象。最终是调用serviceMethod中的toResponse进行转换成对应的T类型。
/** Builds a method return value from an HTTP response body. */
T toResponse(ResponseBody body) throws IOException {
return responseConverter.convert(body);
}所以这里就是使用了我们指定的responseConverter进行转换。如GsonConverterFactory。转换的方式根据不同Converter来定，不做详述。由此可见，通过ServiceMethod的协调完成了request的组装和response回复的转换。