build.gradle
Kotlin
dependencies {
//retrofit + gson + rxjava
implementation 'com.squareup.retrofit2:retrofit:2.9.0'
implementation 'com.squareup.retrofit2:converter-gson:2.5.0'
implementation 'com.squareup.retrofit2:adapter-rxjava2:2.9.0'
}
Kotlin
interface ApiService {
@GET("getUserData")
fun getUserData1(): Call<ResponseBody>
}
fun main1() {
val retrofit = Retrofit.Builder()
.baseUrl("http://mockapi.eolinker.com/9IiwI82f58c23411240ed608ceca204b2f185014507cbe3/")
.build()
val service = retrofit.create(ApiService::class.java)
val call: Call<ResponseBody> = service.getUserData1()
call.enqueue(object : Callback<ResponseBody> {
override fun onResponse(call: Call<ResponseBody>, response: Response<ResponseBody>) {
val userBean = response.body()?.string()
println("userBean: $userBean")
}
override fun onFailure(call: Call<ResponseBody>, t: Throwable) {
println("onFailure: $t")
}
})
}Retrofit 是建立在 OkHttp 之上的一个网络请求封装库，内部依靠 okhttp 来完成实际网络请求。Retrofit 在使用上很简洁， API 通过 interface 来声明。我只需要通过 interface 来声明 API路径、请求方式、请求参数、返回值类型等各个配置项。
可以看到，getUserData() 方法的请求结果是一个 json 格式的字符串，其返回值类型被定义为 Call<ResponseBody> ， 此处的 ResponseBody 即 okHttp3.ResponseBody ,是 okhttp 提供的对网络请求结果的包装类，Call 即 retrofit2.Call ，是 Retrofit 对 okhttp3.Call 做的一层包装，OkHttp在实际发起请求的时候使用的回调是 okhttp3.Call ，回调内部会中转调用 retrofit2.Call，以便将请求结果转交给外部。
1、converter-gson
API 返回值 Json 转换 ：
Kotlin
interface ApiService {
@GET("getUserData")
fun getUserData2(): Call<UserBean>
}
data class UserBean(val status: Int, val msg: String, val data: Data)
data class Data(val userName: String, val userAge: Long)
fun main2() {
val retrofit = Retrofit.Builder()
.baseUrl("http://mockapi.eolinker.com/9IiwI82f58c23411240ed608ceca204b2f185014507cbe3/")
.addConverterFactory(GsonConverterFactory.create())
.build()
val service = retrofit.create(ApiService::class.java)
val call: Call<UserBean> = service.getUserData2()
call.enqueue(object : Callback<UserBean> {
override fun onResponse(call: Call<UserBean>, response: Response<UserBean>) {
val userBean = response.body()
println("userBean: $userBean")
}
override fun onFailure(call: Call<UserBean>, t: Throwable) {
println("onFailure: $t")
}
})
}2、adapter-rxjava2
adapter-rxjava2 转换返回值为被观察者
Kotlin
interface ApiService {
@GET("getUserData")
fun getUserData3(): Observable<UserBean>
}
data class UserBean(val status: Int, val msg: String, val data: Data)
data class Data(val userName: String, val userAge: Long)
fun main3() {
val retrofit = Retrofit.Builder()
.baseUrl("http://mockapi.eolinker.com/9IiwI82f58c23411240ed608ceca204b2f185014507cbe3/")
.addConverterFactory(GsonConverterFactory.create())
.addCallAdapterFactory(RxJava2CallAdapterFactory.create())
.build()
val service = retrofit.create(ApiService::class.java)
val call: Observable<UserBean> = service.getUserData3()
call.subscribe({ user ->
println("userBean: $user")
}, { t ->
println("onFailure: $t")
})
}一、Retrofit请求过程
1、Retrofit.create()
Kotlin
@SuppressWarnings("unchecked") // Single-interface proxy creation guarded by parameter safety.
public <T> T create(final Class<T> service) {
validateServiceInterface(service);
return (T)
Proxy.newProxyInstance(
service.getClassLoader(),
new Class<?>[] {service},
new InvocationHandler() {
private final Platform platform = Platform.get();
private final Object[] emptyArgs = new Object[0];
@Override
public @Nullable 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);
}
args = args != null ? args : emptyArgs;
return platform.isDefaultMethod(method)
? platform.invokeDefaultMethod(method, service, proxy, args)
: loadServiceMethod(method).invoke(args);
}
});
}
Kotlin
ServiceMethod<?> loadServiceMethod(Method method) {
ServiceMethod<?> result = serviceMethodCache.get(method);
if (result != null) return result;
synchronized (serviceMethodCache) {
result = serviceMethodCache.get(method);
if (result == null) {
result = ServiceMethod.parseAnnotations(this, method);
serviceMethodCache.put(method, result);
}
}
return result;
}2、ServiceMethod
Kotlin
abstract class ServiceMethod<T> {
static <T> ServiceMethod<T> parseAnnotations(Retrofit retrofit, Method method) {
RequestFactory requestFactory = RequestFactory.parseAnnotations(retrofit, method);
Type returnType = method.getGenericReturnType();
if (Utils.hasUnresolvableType(returnType)) {
throw methodError(
method,
"Method return type must not include a type variable or wildcard: %s",
returnType);
}
if (returnType == void.class) {
throw methodError(method, "Service methods cannot return void.");
}
return HttpServiceMethod.parseAnnotations(retrofit, method, requestFactory);
}
abstract @Nullable T invoke(Object[] args);
}3、HttpServiceMethod
Kotlin
abstract class HttpServiceMethod<ResponseT, ReturnT> extends ServiceMethod<ReturnT> {
static <ResponseT, ReturnT> HttpServiceMethod<ResponseT, ReturnT> parseAnnotations(
Retrofit retrofit, Method method, RequestFactory requestFactory) {
boolean isKotlinSuspendFunction = requestFactory.isKotlinSuspendFunction;
boolean continuationWantsResponse = false;
boolean continuationBodyNullable = false;
Annotation[] annotations = method.getAnnotations();
Type adapterType;
if (isKotlinSuspendFunction) {
Type[] parameterTypes = method.getGenericParameterTypes();
Type responseType =
Utils.getParameterLowerBound(
0, (ParameterizedType) parameterTypes[parameterTypes.length - 1]);
if (getRawType(responseType) == Response.class && responseType instanceof ParameterizedType) {
// Unwrap the actual body type from Response<T>.
responseType = Utils.getParameterUpperBound(0, (ParameterizedType) responseType);
continuationWantsResponse = true;
} else {
// TODO figure out if type is nullable or not
// Metadata metadata = method.getDeclaringClass().getAnnotation(Metadata.class)
// Find the entry for method
// Determine if return type is nullable or not
}
adapterType = new Utils.ParameterizedTypeImpl(null, Call.class, responseType);
annotations = SkipCallbackExecutorImpl.ensurePresent(annotations);
} else {
adapterType = method.getGenericReturnType();
}
CallAdapter<ResponseT, ReturnT> callAdapter =
createCallAdapter(retrofit, method, adapterType, annotations);
Type responseType = callAdapter.responseType();
if (responseType == okhttp3.Response.class) {
throw methodError(
method,
"'"
+ getRawType(responseType).getName()
+ "' is not a valid response body type. Did you mean ResponseBody?");
}
if (responseType == Response.class) {
throw methodError(method, "Response must include generic type (e.g., Response<String>)");
}
// TODO support Unit for Kotlin?
if (requestFactory.httpMethod.equals("HEAD") && !Void.class.equals(responseType)) {
throw methodError(method, "HEAD method must use Void as response type.");
}
Converter<ResponseBody, ResponseT> responseConverter =
createResponseConverter(retrofit, method, responseType);
okhttp3.Call.Factory callFactory = retrofit.callFactory;
if (!isKotlinSuspendFunction) {
return new CallAdapted<>(requestFactory, callFactory, responseConverter, callAdapter);
} else if (continuationWantsResponse) {
//noinspection unchecked Kotlin compiler guarantees ReturnT to be Object.
return (HttpServiceMethod<ResponseT, ReturnT>)
new SuspendForResponse<>(
requestFactory,
callFactory,
responseConverter,
(CallAdapter<ResponseT, Call<ResponseT>>) callAdapter);
} else {
//noinspection unchecked Kotlin compiler guarantees ReturnT to be Object.
return (HttpServiceMethod<ResponseT, ReturnT>)
new SuspendForBody<>(
requestFactory,
callFactory,
responseConverter,
(CallAdapter<ResponseT, Call<ResponseT>>) callAdapter,
continuationBodyNullable);
}
}
@Override
final @Nullable ReturnT invoke(Object[] args) {
Call<ResponseT> call = new OkHttpCall<>(requestFactory, args, callFactory, responseConverter);
return adapt(call, args);
}
}4、OkHttpCall
OkHttpCall 是实际发起 okHttp 请求的地方。当我们调用 fun getUserData(): Call<ResponseBody> 方法时，返回的 Call 对象实际上是 OkHttp 类型。
Kotlin
final class OkHttpCall<T> implements Call<T> {
private final RequestFactory requestFactory;
private final Object[] args;
private final okhttp3.Call.Factory callFactory;
private final Converter<ResponseBody, T> responseConverter;
private volatile boolean canceled;
@GuardedBy("this")
private @Nullable okhttp3.Call rawCall;
@GuardedBy("this") // Either a RuntimeException, non-fatal Error, or IOException.
private @Nullable Throwable creationFailure;
@GuardedBy("this")
private boolean executed;
OkHttpCall(
RequestFactory requestFactory,
Object[] args,
okhttp3.Call.Factory callFactory,
Converter<ResponseBody, T> responseConverter) {
this.requestFactory = requestFactory;
this.args = args;
this.callFactory = callFactory;
this.responseConverter = responseConverter;
}
@SuppressWarnings("CloneDoesntCallSuperClone") // We are a final type & this saves clearing state.
@Override
public OkHttpCall<T> clone() {
return new OkHttpCall<>(requestFactory, args, callFactory, responseConverter);
}
@Override
public synchronized Request request() {
try {
return getRawCall().request();
} catch (IOException e) {
throw new RuntimeException("Unable to create request.", e);
}
}
@Override
public synchronized Timeout timeout() {
try {
return getRawCall().timeout();
} catch (IOException e) {
throw new RuntimeException("Unable to create call.", e);
}
}
/**
* Returns the raw call, initializing it if necessary. Throws if initializing the raw call throws,
* or has thrown in previous attempts to create it.
*/
@GuardedBy("this")
private okhttp3.Call getRawCall() throws IOException {
okhttp3.Call call = rawCall;
if (call != null) return call;
// Re-throw previous failures if this isn't the first attempt.
if (creationFailure != null) {
if (creationFailure instanceof IOException) {
throw (IOException) creationFailure;
} else if (creationFailure instanceof RuntimeException) {
throw (RuntimeException) creationFailure;
} else {
throw (Error) creationFailure;
}
}
// Create and remember either the success or the failure.
try {
return rawCall = createRawCall();
} catch (RuntimeException | Error | IOException e) {
throwIfFatal(e); // Do not assign a fatal error to creationFailure.
creationFailure = e;
throw e;
}
}
@Override
public void enqueue(final Callback<T> callback) {
Objects.requireNonNull(callback, "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) {
throwIfFatal(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) {
Response<T> response;
try {
response = parseResponse(rawResponse);
} catch (Throwable e) {
throwIfFatal(e);
callFailure(e);
return;
}
try {
callback.onResponse(OkHttpCall.this, response);
} catch (Throwable t) {
throwIfFatal(t);
t.printStackTrace(); // TODO this is not great
}
}
@Override
public void onFailure(okhttp3.Call call, IOException e) {
callFailure(e);
}
private void callFailure(Throwable e) {
try {
callback.onFailure(OkHttpCall.this, e);
} catch (Throwable t) {
throwIfFatal(t);
t.printStackTrace(); // TODO this is not great
}
}
});
}
@Override
public synchronized boolean isExecuted() {
return executed;
}
@Override
public Response<T> execute() throws IOException {
okhttp3.Call call;
synchronized (this) {
if (executed) throw new IllegalStateException("Already executed.");
executed = true;
call = getRawCall();
}
if (canceled) {
call.cancel();
}
return parseResponse(call.execute());
}
}5、RequestFactory
Kotlin
final class RequestFactory {
static RequestFactory parseAnnotations(Retrofit retrofit, Method method) {
return new Builder(retrofit, method).build();
}
private final Method method;
private final HttpUrl baseUrl;
final String httpMethod;
private final @Nullable String relativeUrl;
private final @Nullable Headers headers;
private final @Nullable MediaType contentType;
private final boolean hasBody;
private final boolean isFormEncoded;
private final boolean isMultipart;
private final ParameterHandler<?>[] parameterHandlers;
final boolean isKotlinSuspendFunction;
RequestFactory(Builder builder) {
method = builder.method;
baseUrl = builder.retrofit.baseUrl;
httpMethod = builder.httpMethod;
relativeUrl = builder.relativeUrl;
headers = builder.headers;
contentType = builder.contentType;
hasBody = builder.hasBody;
isFormEncoded = builder.isFormEncoded;
isMultipart = builder.isMultipart;
parameterHandlers = builder.parameterHandlers;
isKotlinSuspendFunction = builder.isKotlinSuspendFunction;
}
okhttp3.Request create(Object[] args) throws IOException {
@SuppressWarnings("unchecked") // It is an error to invoke a method with the wrong arg types.
ParameterHandler<Object>[] handlers = (ParameterHandler<Object>[]) parameterHandlers;
int argumentCount = args.length;
if (argumentCount != handlers.length) {
throw new IllegalArgumentException(
"Argument count ("
+ argumentCount
+ ") doesn't match expected count ("
+ handlers.length
+ ")");
}
RequestBuilder requestBuilder =
new RequestBuilder(
httpMethod,
baseUrl,
relativeUrl,
headers,
contentType,
hasBody,
isFormEncoded,
isMultipart);
if (isKotlinSuspendFunction) {
// The Continuation is the last parameter and the handlers array contains null at that index.
argumentCount--;
}
List<Object> argumentList = new ArrayList<>(argumentCount);
for (int p = 0; p < argumentCount; p++) {
argumentList.add(args[p]);
handlers[p].apply(requestBuilder, args[p]);
}
return requestBuilder.get().tag(Invocation.class, new Invocation(method, argumentList)).build();
}
/**
* Inspects the annotations on an interface method to construct a reusable service method. This
* requires potentially-expensive reflection so it is best to build each service method only once
* and reuse it. Builders cannot be reused.
*/
static final class Builder {
// Upper and lower characters, digits, underscores, and hyphens, starting with a character.
private static final String PARAM = "[a-zA-Z][a-zA-Z0-9_-]*";
private static final Pattern PARAM_URL_REGEX = Pattern.compile("\\{(" + PARAM + ")\\}");
private static final Pattern PARAM_NAME_REGEX = Pattern.compile(PARAM);
final Retrofit retrofit;
final Method method;
final Annotation[] methodAnnotations;
final Annotation[][] parameterAnnotationsArray;
final Type[] parameterTypes;
boolean gotField;
boolean gotPart;
boolean gotBody;
boolean gotPath;
boolean gotQuery;
boolean gotQueryName;
boolean gotQueryMap;
boolean gotUrl;
@Nullable String httpMethod;
boolean hasBody;
boolean isFormEncoded;
boolean isMultipart;
@Nullable String relativeUrl;
@Nullable Headers headers;
@Nullable MediaType contentType;
@Nullable Set<String> relativeUrlParamNames;
@Nullable ParameterHandler<?>[] parameterHandlers;
boolean isKotlinSuspendFunction;
Builder(Retrofit retrofit, Method method) {
this.retrofit = retrofit;
this.method = method;
this.methodAnnotations = method.getAnnotations();
this.parameterTypes = method.getGenericParameterTypes();
this.parameterAnnotationsArray = method.getParameterAnnotations();
}
RequestFactory build() {
for (Annotation annotation : methodAnnotations) {
parseMethodAnnotation(annotation);
}
if (httpMethod == null) {
throw methodError(method, "HTTP method annotation is required (e.g., @GET, @POST, etc.).");
}
if (!hasBody) {
if (isMultipart) {
throw methodError(
method,
"Multipart can only be specified on HTTP methods with request body (e.g., @POST).");
}
if (isFormEncoded) {
throw methodError(
method,
"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, lastParameter = parameterCount - 1; p < parameterCount; p++) {
parameterHandlers[p] =
parseParameter(p, parameterTypes[p], parameterAnnotationsArray[p], p == lastParameter);
}
if (relativeUrl == null && !gotUrl) {
throw methodError(method, "Missing either @%s URL or @Url parameter.", httpMethod);
}
if (!isFormEncoded && !isMultipart && !hasBody && gotBody) {
throw methodError(method, "Non-body HTTP method cannot contain @Body.");
}
if (isFormEncoded && !gotField) {
throw methodError(method, "Form-encoded method must contain at least one @Field.");
}
if (isMultipart && !gotPart) {
throw methodError(method, "Multipart method must contain at least one @Part.");
}
return new RequestFactory(this);
}
}参考：