RxJava + Retrofit怎么请求网络,具体的用法这里就不讲了,本文只讲一些重点源码。
版本如下:
okhttp : "com.squareup.okhttp3:okhttp:3.10.0",
okhttp3_integration :"com.github.bumptech.glide:okhttp3-integration:1.4.0@aar",
retrofit :"com.squareup.retrofit2:retrofit:2.4.0",
converter_gson :"com.squareup.retrofit2:converter-gson:2.3.0",
converter_scalars :"com.squareup.retrofit2:converter-scalars:2.3.0",
converter_protobuf :"com.squareup.retrofit2:converter-protobuf:2.3.0",
adapter_rxjava2 :"com.squareup.retrofit2:adapter-rxjava2:2.2.0",
logging_interceptor :"com.squareup.okhttp3:logging-interceptor:3.10.0",
rxjava :"io.reactivex.rxjava2:rxjava:2.1.12",
rxandroid :"io.reactivex.rxjava2:rxandroid:2.0.2",
一、首先关于Retrofit的初始化:
privatevoid initRetrofit() {
ExtensionRegistry extensionRegistry= ExtensionRegistry.newInstance();
retrofit=new Retrofit.Builder()
.baseUrl(baseUrl)//设置地址
.client(client.build())//设置自定义的OkHttpClient
.addConverterFactory(ProtoConverterFactory.createWithRegistry(extensionRegistry))
.addConverterFactory(StringConverterFactory.create())
.addConverterFactory(GsonConverterFactory.create(buildGson()))
.addCallAdapterFactory(RxJava2CallAdapterFactory.create())
.build();
service= retrofit.create(ApiService.class);
}
.addConverterFactory(ProtoConverterFactory.createWithRegistry(extensionRegistry))
.addConverterFactory(StringConverterFactory.create())
.addConverterFactory(GsonConverterFactory.create(buildGson()))
.addCallAdapterFactory(RxJava2CallAdapterFactory.create())
添加了数据转换器与请求适配器。
Retrofit的初始化采用了Builder模式。
Retrofit.Builder()这一步,获取了一个平台,肯定就是Android()了,后面有地方会用到。
Builder(Platform platform) {this.platform = platform;
}public Builder() {this(Platform.get());
}class Platform {privatestaticfinal Platform PLATFORM = findPlatform();static Platform get() {return PLATFORM;
}privatestatic Platform findPlatform() {try {
Class.forName("android.os.Build");if (Build.VERSION.SDK_INT != 0) {returnnew Android();
}
}catch (ClassNotFoundException ignored) {
}try {
Class.forName("java.util.Optional");returnnew Java8();
}catch (ClassNotFoundException ignored) {
}returnnew Platform();
}
}
在看最后的build();方法:
public Retrofit build() {if (baseUrl ==null) {thrownew 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<CallAdapter.Factory> callAdapterFactories =new ArrayList<>(this.callAdapterFactories);
callAdapterFactories.add(platform.defaultCallAdapterFactory(callbackExecutor));// Make a defensive copy of the converters.
List<Converter.Factory> converterFactories =new ArrayList<>(1 +this.converterFactories.size());// Add the built-in converter factory first. This prevents overriding its behavior but also// ensures correct behavior when using converters that consume all types.
converterFactories.add(new BuiltInConverters());
converterFactories.addAll(this.converterFactories);returnnew Retrofit(callFactory, baseUrl, unmodifiableList(converterFactories),
unmodifiableList(callAdapterFactories), callbackExecutor, validateEagerly);
}
1、如果没有传入我们自定义的OkHttpClient,那么便会使用默认的。
2、如果没有设置自定义的回调执行器,那么便会是用默认的platform.defaultCallbackExecutor();点进入可以发现回调是默认在主线程中的:
staticclass Androidextends Platform {
@Overridepublic Executor defaultCallbackExecutor() {returnnew MainThreadExecutor();
}
@Override CallAdapter.Factory defaultCallAdapterFactory(@Nullable Executor callbackExecutor) {if (callbackExecutor ==null)thrownew AssertionError();returnnew ExecutorCallAdapterFactory(callbackExecutor);
}staticclass MainThreadExecutorimplements Executor {privatefinal Handler handler =new Handler(Looper.getMainLooper());
@Overridepublicvoid execute(Runnable r) {
handler.post(r);
}
}
}
3、把我们设置的请求适配器添加进入,然后再添加一个默认的请求适配器。
4、添加进入一个默认的数据转换器,然后再被我们设置的数据转换器添加进去。
二、初始化好Retrofit后,再来看这一句:
service = retrofit.create(ApiService.class);
ApiService是一个接口,里面方法如下:
@GET
Observable<ResponseBody> doGet(@Url String url, @HeaderMap Map<String, String> headers, @QueryMap Map<String, String> map);
这个create方法可以说是核心,它运用的是动态代理。
@SuppressWarnings("unchecked")// Single-interface proxy creation guarded by parameter safety.public <T> T create(final Class<T> service) {
Utils.validateServiceInterface(service);if (validateEagerly) {
eagerlyValidateMethods(service);
}return (T) Proxy.newProxyInstance(service.getClassLoader(),new Class<?>[] { service },new InvocationHandler() {privatefinal Platform platform = Platform.get();
@Overridepublic 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<Object, Object> serviceMethod =
(ServiceMethod<Object, Object>) loadServiceMethod(method);
OkHttpCall<Object> okHttpCall =new OkHttpCall<>(serviceMethod, args);return serviceMethod.adapt(okHttpCall);
}
});
}
1、首先检测这是否是一个接口,只有接口才能对它进行动态代理。
2、是否需要对接口里面的方法进行初始化预加载,是的话便进行,这个与下面的有点重复,直接讲下面的。
3、return后面的语句便是动态代理的地方,它会代理接口的所有方法,也就是说,当我们调用ApiService的方法的时候,会被拦截,然后走到inoke这个方法做我们自己的操作。
关于动态代理,后面会单独讲。
4、接下来边看invoke方法:
(1)、首先判断该方法是否为Object这个类的方法,如果是,不拦截它,让他走原来的方法。
(2)、platform为Android,platform.isDefaultMethod(method)返回false,不用管它。
(3)、ServiceMethod<Object, Object> serviceMethod =(ServiceMethod<Object, Object>) loadServiceMethod(method);拿到接口的方法,对接口的方法进行解析,比如获取注解,参数之类,构造自己的serviceMethod
(4)、初始化OkHttpCall
(5)、调用serviceMethod.adapt(okHttpCall)进行请求(因为采用的是RxJava,所以这里并不会立即请求,只有被订阅的时候才会,等会会讲)
三、loadServiceMethod(method)方法:
构造自己的serviceMethod 也采用了Builder模式。
进入这个方法后,重点的一句:
result =new ServiceMethod.Builder<>(this, method).build();
先看:
Builder(Retrofit retrofit, Method method) {this.retrofit = retrofit;this.method = method;this.methodAnnotations = method.getAnnotations();this.parameterTypes = method.getGenericParameterTypes();this.parameterAnnotationsArray = method.getParameterAnnotations();
}
注:我们这里以前面定义的方法来讲解:
@GET
Observable<ResponseBody> doGet(@Url String url, @HeaderMap Map<String, String> headers, @QueryMap Map<String, String> map);
1、持有retrofit与原始的method对象。
2、获取方法上的注解,获取到的为:
3、获取参数类型,获取到的为:
4、获取参数上面的的注解,获取到的为:
再看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;
if (Utils.hasUnresolvableType(parameterType)) {throw parameterError(p, "Parameter type must not include a type variable or wildcard: %s",
parameterType);
}
Annotation[] parameterAnnotations= parameterAnnotationsArray;
if (parameterAnnotations ==null) {throw parameterError(p, "No Retrofit annotation found.");
}
parameterHandlers= 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.");
}returnnew ServiceMethod<>(this);
}
1、首先获取请求适配器。
2、创建请求结果的转换器。
3、对方法上的注解进行解析。
4、构造ParameterHandler数组。
5、对一些异常的判断。
四、我们接下来对每一步进行讲解。
1、首先获取请求适配器:
private CallAdapter<T, R> createCallAdapter() {
Type returnType= method.getGenericReturnType();if (Utils.hasUnresolvableType(returnType)) {throw methodError("Method return type must not include a type variable or wildcard: %s", returnType);
}if (returnType ==void.class) {throw methodError("Service methods cannot return void.");
}
Annotation[] annotations= method.getAnnotations();try {//noinspection uncheckedreturn (CallAdapter<T, R>) retrofit.callAdapter(returnType, annotations);
}catch (RuntimeException e) {// Wide exception range because factories are user code.throw methodError(e, "Unable to create call adapter for %s", returnType);
}
}
(1)、获取方法的返回类型,返回类型不能是void
(2)、获取方法上的注解。
(3)、调用retrofit.callAdapter(returnType, annotations)方法获取请求的适配器。(我们之前设置的请求适配器都在retrofit对象中)
里面关键的一步为:
int start = callAdapterFactories.indexOf(skipPast) + 1;for (int i = start, count = callAdapterFactories.size(); i < count; i++) {
CallAdapter<?, ?> adapter = callAdapterFactories.get(i).get(returnType, annotations,this);if (adapter !=null) {return adapter;
}
}
skipPast为null,所以start为0;
遍历我们之前设置给它的请求适配器,根据返回类型与方法上的注解去找,找到了便返回。(我们这里获取到的callAdapter为RxJava2CallAdapter)
2、创建请求结果的转换器:
responseConverter = createResponseConverter()
这个与获取请求的适配器的过程是类似的,因此这里就略过了。
3、解析方法上的注解:parseMethodAnnotation(annotation),我们用的是GET,所以下面会调用:
parseHttpMethodAndPath("GET", ((GET) annotation).value(), false);
我们这里value是空的,所以它只走了下面这些就返回了。
if (this.httpMethod !=null) {throw methodError("Only one HTTP method is allowed. Found: %s and %s.",this.httpMethod, httpMethod);
}this.httpMethod = httpMethod;this.hasBody = hasBody;if (value.isEmpty()) {return;
}
4、构造ParameterHandler数组
int parameterCount = parameterAnnotationsArray.length;
parameterHandlers=new ParameterHandler<?>[parameterCount];for (int p = 0; p < parameterCount; p++) {
Type parameterType= parameterTypes;
if (Utils.hasUnresolvableType(parameterType)) {throw parameterError(p, "Parameter type must not include a type variable or wildcard: %s",
parameterType);
}
Annotation[] parameterAnnotations= parameterAnnotationsArray;
if (parameterAnnotations ==null) {throw parameterError(p, "No Retrofit annotation found.");
}
parameterHandlers= parseParameter(p, parameterType, parameterAnnotations);
}
主要是这一个方法:
parameterHandlers = parseParameter(p, parameterType, parameterAnnotations);
p为序号,parameterType为方法的参数类型,parameterAnnotations为参数的注解。
里面就不细讲了,这里最终得到的是:
对于一些异常的判断就不多讲了,比如:
不能有多个带@Url注解的参数。
不能同时使用@Path与@Url注解。
被@QueryMap标注的参数类型必须是Map
@QueryMap注解的参数的key必须是String
至此,我们的ServiceMethod便构造完了。
五、我们回到代理的那个方法里面,还差两句没有解析:
OkHttpCall<Object> okHttpCall = new OkHttpCall<>(serviceMethod, args);
return serviceMethod.adapt(okHttpCall);
主要看serviceMethod.adapt(okHttpCall)
T adapt(Call<R> call) {return callAdapter.adapt(call);
}
这里的callAdapter是RxJava2CallAdapter。
于是我们来到它的adapter方法:
@Overridepublic Object adapt(Call<R> call) {
Observable<Response<R>> responseObservable = isAsync?new CallEnqueueObservable<>(call)
:new CallExecuteObservable<>(call);
Observable<?> observable;if (isResult) {
observable=new ResultObservable<>(responseObservable);
}elseif (isBody) {
observable=new BodyObservable<>(responseObservable);
}else {
observable= responseObservable;
}if (scheduler !=null) {
observable= observable.subscribeOn(scheduler);
}if (isFlowable) {return observable.toFlowable(BackpressureStrategy.LATEST);
}if (isSingle) {return observable.singleOrError();
}if (isMaybe) {return observable.singleElement();
}if (isCompletable) {return observable.ignoreElements();
}return observable;
}
首先我们看isAsync,这里为false,为什么呢?我们创建adapter的时候是这样的:
RxJava2CallAdapterFactory.create()
publicstatic RxJava2CallAdapterFactory create() {returnnew RxJava2CallAdapterFactory(null,false);
}
第二个参数便是isAsync
1、所以我们创建的responseObservable为CallExecuteObservable<>(call),(同步执行的类)
2、我们创建一个Observable<?> observable,这里创建的是BodyObservable<>(responseObservable),将刚刚创建的responseObservable
传进去。
3、最终将该observable传出去。
service = retrofit.create(ApiService.class);publicinterface ApiService {
@GET
Observable<ResponseBody> doGet(@Url String url, @HeaderMap Map<String, String> headers, @QueryMap Map<String, String> map);
}
service.doGet(url, header, params?.params)
也就是说,当我们调用service.doGet的时候,会走到代理的invoke方法,然后返回一个Observable
而该Observable只有在被订阅的时候才会执行,而且我们用的是同步,所以还需要在外面自己切换到子线程执行。
当被订阅的时候,该BodyObservable会调用subscribeActual:
BodyObservable(Observable<Response<T>> upstream) {this.upstream = upstream;
}
@Overrideprotectedvoid subscribeActual(Observer<?super T> observer) {
upstream.subscribe(new BodyObserver<T>(observer));
}
而这个upstream便是刚刚传进去的responseObservable,调用subscribe方法,最终会执行到responseObservable的subscribeActual方法。
@Overrideprotectedvoid subscribeActual(Observer<?super Response<T>> observer) {// Since Call is a one-shot type, clone it for each new observer.
Call<T> call = originalCall.clone();
observer.onSubscribe(new CallDisposable(call));boolean terminated =false;try {
Response<T> response = call.execute();if (!call.isCanceled()) {
observer.onNext(response);
}if (!call.isCanceled()) {
terminated=true;
observer.onComplete();
}
}catch (Throwable t) {
Exceptions.throwIfFatal(t);if (terminated) {
RxJavaPlugins.onError(t);
}elseif (!call.isCanceled()) {try {
observer.onError(t);
}catch (Throwable inner) {
Exceptions.throwIfFatal(inner);
RxJavaPlugins.onError(new CompositeException(t, inner));
}
}
}
}
我们主要看Response<T> response = call.execute();call便是我们传进来的自定义的OkHttpCall
在call.execute()里面:
.
.
.
call= rawCall;if (call ==null) {try {
call= rawCall = createRawCall();
}catch (IOException | RuntimeException | Error e) {
throwIfFatal(e);// Do not assign a fatal error to creationFailure.
creationFailure = e;throw e;
}
}
.
.
.return parseResponse(call.execute());
createRawCall()获取okhttp3.Call,call.execute()便是okhttp的网络请求了。
我们主要看怎么获取okhttp3.Call,以及对请求结果的解析parseResponse方法。
private okhttp3.Call createRawCall()throws IOException {
okhttp3.Call call= serviceMethod.toCall(args);if (call ==null) {thrownew NullPointerException("Call.Factory returned null.");
}return call;
}
ServiceMethod里面:
/** Builds an HTTP request from method arguments.*/
okhttp3.Call toCall(@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.
ParameterHandler<Object>[] handlers = (ParameterHandler<Object>[]) parameterHandlers;int argumentCount = args !=null ? args.length : 0;if (argumentCount != handlers.length) {thrownew IllegalArgumentException("Argument count (" + argumentCount+ ") doesn't match expected count (" + handlers.length + ")");
}for (int p = 0; p < argumentCount; p++) {
handlers.apply(requestBuilder, args
);
}
return callFactory.newCall(requestBuilder.build());
}
方法主要是构造了request然后使用okhttp3.Call.Factory创建okhttp3.Call,而我们之前在构建ServiceMothod的构造的ParameterHandler<Object>[] handlers便参与了request的构建,主要是将之前解析到的参数,比如路径,头部信息等添加到request里面。
再看一下请求结果的解析parseResponse方法:
重点语句:
T body = serviceMethod.toResponse(catchingBody);
在看serviceMethod里面的toResponse方法:
/** Builds a method return value from an HTTP response body.*/
R toResponse(ResponseBody body)throws IOException {return responseConverter.convert(body);
}
这里便用到了我们之前设置的数据转换器,对结果进行转换。
以上便是大概的过程了。