源码解析
(1)跟进create方法
MyInterface myInterface = retrofit.create(MyInterface.class);
public <T> T create(final Class<T> service) {
Utils.validateServiceInterface(service);
if (this.validateEagerly) {
(1)解析接口方法，并放入缓存
this.eagerlyValidateMethods(service);
}
（1）动态代理,生成一个代理类的实例
return Proxy.newProxyInstance(service.getClassLoader(), new Class[]{service}, new InvocationHandler() {
private final Platform platform = Platform.get();
public Object invoke(Object proxy, Method method, Object... args) throws Throwable {
if (method.getDeclaringClass() == Object.class) {
return method.invoke(this, args);
} else if (this.platform.isDefaultMethod(method)) {
return this.platform.invokeDefaultMethod(method, service, proxy, args);
} else {
（2）重点关注这三行代码
ServiceMethod serviceMethod = Retrofit.this.loadServiceMethod(method);
（3）构建OkhttpCall
OkHttpCall okHttpCall = new OkHttpCall(serviceMethod, args);
（4）通过适配器转将Retrofit的Call转换成其他平台可以执行的Call（例如Rxjava）
return serviceMethod.callAdapter.adapt(okHttpCall);
}
}
});
}
这篇重点关注ServiceMethod的创建。
构建 ServiceMethod
成员变量
包含了网络请求的所有基本信息
final class ServiceMethod<R, T> {
// Upper and lower characters, digits, underscores, and hyphens, starting with a character.
static final String PARAM = "[a-zA-Z][a-zA-Z0-9_-]*";
static final Pattern PARAM_URL_REGEX = Pattern.compile("\{(" + PARAM + ")\}");
static final Pattern PARAM_NAME_REGEX = Pattern.compile(PARAM);
(1)网络请求工厂
final okhttp3.Call.Factory callFactory;
（2）适配器
final CallAdapter<R, T> callAdapter;
（3）Retrofit网络请求的Url
private final HttpUrl baseUrl;
（4）服务器返回数据转换java对象
private final Converter<ResponseBody, R> responseConverter;
（5）请求的方法例如GET，POST
private final String httpMethod;
（6）请求的相对路径
private final String relativeUrl;
（7）请求头
private final Headers headers;
（8）请求类型
private final MediaType contentType;
private final boolean hasBody;
private final boolean isFormEncoded;
private final boolean isMultipart;
（9）方法参数解析处理器
private final ParameterHandler<?>[] parameterHandlers;
}
构造方法
Builder(Retrofit retrofit, Method method) {
this.retrofit = retrofit;
this.method = method;
（1）获取方法注解
this.methodAnnotations = method.getAnnotations();
（2）获取方法参数的类型
this.parameterTypes = method.getGenericParameterTypes();
（3）获取方法注解内容
this.parameterAnnotationsArray = method.getParameterAnnotations();
}
build方法
public ServiceMethod build() {
（1）创建网络适配器
（2）跟进去看下
callAdapter = createCallAdapter();
（3）拿到网络适配器返回的类型()例如Call<List<Repo>> 就是<List<Repo>
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?");
}
（4）创建数据转换器
responseConverter = createResponseConverter();
（5）遍历解析方法的注解
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.");
}
（6）解析方法请求中的参数
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.");
}
（7）返回
return new ServiceMethod<>(this);
}
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 unchecked
（1）跟进去看下
return (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);
}
}
public CallAdapter<?, ?> callAdapter(Type returnType, Annotation[] annotations) {
return nextCallAdapter(null, returnType, annotations);
}
/**
* Returns the {@link CallAdapter} for {@code returnType} from the available {@linkplain
* #callAdapterFactories() factories} except {@code skipPast}.
*
* @throws IllegalArgumentException if no call adapter available for {@code type}.
*/
public CallAdapter<?, ?> nextCallAdapter(CallAdapter.Factory skipPast, Type returnType,
Annotation[] annotations) {
checkNotNull(returnType, "returnType == null");
checkNotNull(annotations, "annotations == null");
int start = adapterFactories.indexOf(skipPast) + 1;
for (int i = start, count = adapterFactories.size(); i < count; i++) {
（1）从工厂里面遍历寻找合适的CallAdapter。
CallAdapter<?, ?> adapter = adapterFactories.get(i).get(returnType, annotations, this);
if (adapter != null) {
return adapter;
}
}
StringBuilder builder = new StringBuilder("Could not locate call adapter for ")
.append(returnType)
.append(".\n");
if (skipPast != null) {
builder.append(" Skipped:");
for (int i = 0; i < start; i++) {
builder.append("\n * ").append(adapterFactories.get(i).getClass().getName());
}
builder.append('\n');
}
builder.append(" Tried:");
for (int i = start, count = adapterFactories.size(); i < count; i++) {
builder.append("\n * ").append(adapterFactories.get(i).getClass().getName());
}
throw new IllegalArgumentException(builder.toString());
}
final class ExecutorCallAdapterFactory extends CallAdapter.Factory {
final Executor callbackExecutor;
ExecutorCallAdapterFactory(Executor callbackExecutor) {
this.callbackExecutor = callbackExecutor;
}
@Override
public CallAdapter<?, ?> get(Type returnType, Annotation[] annotations, Retrofit retrofit) {
（1）如果返回类型不是Call就直接返回
if (getRawType(returnType) != Call.class) {
return null;
}
final Type responseType = Utils.getCallResponseType(returnType);
return new CallAdapter<Object, Call<?>>() {
@Override public Type responseType() {
return responseType;
}
@Override public Call<Object> adapt(Call<Object> call) {
return new ExecutorCallbackCall<>(callbackExecutor, call);
}
};
}
static final class ExecutorCallbackCall<T> implements Call<T> {
final Executor callbackExecutor;
final Call<T> delegate;
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");
（1）delegate 是 ExecutorCallbackCall 构建时传入的 OkHttpCall 对象
delegate.enqueue(new Callback<T>() {
@Override public void onResponse(Call<T> call, final Response<T> response) {
（2）切换回主线程
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);
}
});
}
});
}
@Override public boolean isExecuted() {
return delegate.isExecuted();
}
@Override public Response<T> 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<T> clone() {
return new ExecutorCallbackCall<>(callbackExecutor, delegate.clone());
}
@Override public Request request() {
return delegate.request();
}
}
}
遍历解析注解
private Converter<ResponseBody, T> createResponseConverter() {
Annotation[] annotations = method.getAnnotations();
try {
（1）跟进去
return retrofit.responseBodyConverter(responseType, annotations);
} catch (RuntimeException e) { // Wide exception range because factories are user code.
throw methodError(e, "Unable to create converter for %s", responseType);
}
}
public <T> Converter<ResponseBody, T> responseBodyConverter(Type type, Annotation[] annotations) {
return nextResponseBodyConverter(null, type, annotations);
}
/**
* Returns a {@link Converter} for {@link ResponseBody} to {@code type} from the available
* {@linkplain #converterFactories() factories} except {@code skipPast}.
*
* @throws IllegalArgumentException if no converter available for {@code type}.
*/
public <T> Converter<ResponseBody, T> nextResponseBodyConverter(Converter.Factory skipPast,
Type type, Annotation[] annotations) {
checkNotNull(type, "type == null");
checkNotNull(annotations, "annotations == null");
int start = converterFactories.indexOf(skipPast) + 1;
for (int i = start, count = converterFactories.size(); i < count; i++) {
（1）一样的逻辑，从数据转换器工厂里面找一个合适的。
Converter<ResponseBody, ?> converter =
converterFactories.get(i).responseBodyConverter(type, annotations, this);
if (converter != null) {
//noinspection unchecked
return (Converter<ResponseBody, T>) converter;
}
}
StringBuilder builder = new StringBuilder("Could not locate ResponseBody converter for ")
.append(type)
.append(".\n");
if (skipPast != null) {
builder.append(" Skipped:");
for (int i = 0; i < start; i++) {
builder.append("\n * ").append(converterFactories.get(i).getClass().getName());
}
builder.append('\n');
}
builder.append(" Tried:");
for (int i = start, count = converterFactories.size(); i < count; i++) {
builder.append("\n * ").append(converterFactories.get(i).getClass().getName());
}
throw new IllegalArgumentException(builder.toString());
}
private void parseMethodAnnotation(Annotation annotation) {
if (annotation instanceof DELETE) {
parseHttpMethodAndPath("DELETE", ((DELETE) annotation).value(), false);
} else if (annotation instanceof GET) {
parseHttpMethodAndPath("GET", ((GET) annotation).value(), false);
} else if (annotation instanceof HEAD) {
parseHttpMethodAndPath("HEAD", ((HEAD) annotation).value(), false);
if (!Void.class.equals(responseType)) {
throw methodError("HEAD method must use Void as response type.");
}
} else if (annotation instanceof PATCH) {
parseHttpMethodAndPath("PATCH", ((PATCH) annotation).value(), true);
} else if (annotation instanceof POST) {
parseHttpMethodAndPath("POST", ((POST) annotation).value(), true);
} else if (annotation instanceof PUT) {
parseHttpMethodAndPath("PUT", ((PUT) annotation).value(), true);
} else if (annotation instanceof OPTIONS) {
parseHttpMethodAndPath("OPTIONS", ((OPTIONS) annotation).value(), false);
} else if (annotation instanceof HTTP) {
HTTP http = (HTTP) annotation;
parseHttpMethodAndPath(http.method(), http.path(), http.hasBody());
} else if (annotation instanceof retrofit2.http.Headers) {
String[] headersToParse = ((retrofit2.http.Headers) annotation).value();
if (headersToParse.length == 0) {
throw methodError("@Headers annotation is empty.");
}
headers = parseHeaders(headersToParse);
} else if (annotation instanceof Multipart) {
if (isFormEncoded) {
throw methodError("Only one encoding annotation is allowed.");
}
isMultipart = true;
} else if (annotation instanceof FormUrlEncoded) {
if (isMultipart) {
throw methodError("Only one encoding annotation is allowed.");
}
isFormEncoded = true;
}
}
private void parseHttpMethodAndPath(String httpMethod, String value, boolean hasBody) {
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;
}
// Get the relative URL path and existing query string, if present.
int question = value.indexOf('?');
if (question != -1 && question < value.length() - 1) {
// Ensure the query string does not have any named parameters.
String queryParams = value.substring(question + 1);
Matcher queryParamMatcher = PARAM_URL_REGEX.matcher(queryParams);
if (queryParamMatcher.find()) {
throw methodError("URL query string "%s" must not have replace block. "
+ "For dynamic query parameters use @Query.", queryParams);
}
}
this.relativeUrl = value;
this.relativeUrlParamNames = parsePathParameters(value);
}
总结
- 根据方法返回类型和方法注解创建适配器。
- 根据适配器返回类型和方法注解创建数据解析工厂。
- 解析方法中的注解，(请求方式，GET POST，还有相对地址)。
- 解析方法参数的注解。
- 创建ServiceMethod并返回。
