本片文章的主要内容如下:
其实整个Retrofit的流程如下图:
retrofit.png
PS:该图不是我画的,网上盗来的
单一流程.png
Retrofit总体使用的是外观模式,Retrofit持有所有子系统的引用;Retrofit有两个比较重要的两个Factory,一个是用来生成对应"Call"的CallAdapter的CallAdapterFactory;一个是用来进行响应数据转化(反序列化)的ConvertFactory;这两个都可以用户自己进行添加。在自定义的Service中,每一个method一一对应一个ServiceMethod,而ServiceMethod持有一个Retrofit,前面两个Factory以及生成的Request的RequestBuilder;在okHttp中,Request需要自己进行定义创建,而Retrofit简化了这个操作,进行相应的封装,使用注解的方式来定义RequestBuilder相关参数信息;注解信息的解析则在parseMethodAnnotation()方法里面和parseParameterAnnotation()方法里面分别解析方法注解和参数注解。最终通过RequestBuilder来具体陈生一个Request,RequestBuilder中持有okHttp中的Request.Builder类的引用,其创建Request的过程其实都是交给okHttp来操作的;生成的Request最终封装成一个OkHttpCall,OkHttpCall则可以看做是对okHttp中Call的代理,同时对okHttp的返回Response进行解析,使用convertFactory将其解析为用户所期望的返回类型。
我们讲解Retrofit整体流程,就依据官方给的demo来吧,代码如下: 代码如下:
public interface GitHub {
@GET("/repos/{owner}/{repo}/contributors")
Call<List<Contributor>> contributors(
@Path("owner") String owner,
@Path("repo") String repo);
}
public static void main(String... args) throws IOException {
Retrofit retrofit = new Retrofit.Builder()
.baseUrl(API_URL)
.addConverterFactory(GsonConverterFactory.create())
.build();
GitHub github = retrofit.create(GitHub.class);
Call<List<Contributor>> call = github.contributors("square", "retrofit");
List<Contributor> contributors = call.execute().body();
for (Contributor contributor : contributors) {
System.out.println(contributor.login + " (" + contributor.contributions + ")");
}
}
这就是Retrofit最简单的用法,可以从代码看出:
(3).用retrofit.create(GitHub.class)方法得到了GitHub实例对象(框架用动态代理的方式帮我们生成了接口的实例,后续详细说),调用对象方法得到call对象。其中,call对象有excute()和enqueue()方法,分别为同步和异步进行网络请求。
所以我们把整个流程分解为5大部分
具体代码如下:
.baseUrl(API_URL)
.addConverterFactory(GsonConverterFactory.create())
.build();
Retrofit的构建,其实就是一个简单的建造者模式(Builder),通过Builder来进行构建。如下图所示:
Retrofit.Builder.png
其中Retrofit.Builder有以下参数可以设置:
补充说明:
下面我们重点说下build()方法的内容: 代码如下;
public Retrofit build() {
if (baseUrl == null) {
throw new IllegalStateException("Base URL required.");
}
// 创建OkHttp,目前Retrofit只支持OkHttp
okhttp3.Call.Factory callFactory = this.callFactory;
if (callFactory == null) {
callFactory = new OkHttpClient();
}
// 创建Executor
Executor callbackExecutor = this.callbackExecutor;
if (callbackExecutor == null) {
callbackExecutor = platform.defaultCallbackExecutor();
}
// 对adapters进行保护性拷贝,并且加入默认的call adapter(使用上面创建的Executor来构建,可以认为是把主线程中的Handler传入, 构建adapterFactories集合,将defaultAdapterFactory加入其中
List<CallAdapter.Factory> adapterFactories = new ArrayList<>(this.adapterFactories);
adapterFactories.add(platform.defaultCallAdapterFactory(callbackExecutor));
// 对converters进行保护性拷贝,一般传入的为GsonConverterFactory对象,其作用主要是将json转换成java对象
List<Converter.Factory> converterFactories = new ArrayList<>(this.converterFactories);
//构建Retrofit对象
return new Retrofit(callFactory, baseUrl, converterFactories, adapterFactories,
callbackExecutor, validateEagerly);
}
build方法主要思路:
PS: ExecutorCallbackCall类里面有个变量叫做final retrofit2.Call<T> delegate,而这个retrofit2.Call的具体实现类是retrofit2.OkHttpCall,在OkHttpCall类内部有一个变量就叫做 private okhttp3.Call rawCall;这样ExecutorCallbackCall就间接持有一个okhttp3.Call的对象了,如下图:
ExecutorCallbackCall.png
@GET("/repos/{owner}/{repo}/contributors")
Call<List<Contributor>> contributors(@Path("owner") String owner, @Path("repo") String repo);
关于两个注解:@GET 和 @Path,我这里就不详细说明了,不懂的看我前面的文章。
GitHub github = retrofit.create(GitHub.class);
调用retrofit.create(GitHubService.class)我们就可以获取一个实例了 这里面我们详细分析下:
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() {
private final Platform platform = Platform.get();
@Override public Object invoke(Object proxy, Method method, Object[] args)
throws Throwable {
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.callAdapter.adapt(okHttpCall);
}
});
}
流程图如下:
流程.png
这里面运用了动态代理技术,动态代理方法Proxy.newProxyInstance返回的便是该接口的代理对象。invoke方法为接口方法的具体实现,invoke()方法里面的method为具体的方法(在demo中为contributors方法);args是该方法的参数(在demo中为new String[]{"square", "retrofit"})。
动态代理模型如下:
动态代理.png
如果大家对这块技术不是很熟悉请看我上一篇文章。
大家看下这块代码:
if (validateEagerly) {
eagerlyValidateMethods(service);
}
private void eagerlyValidateMethods(Class<?> service) {
Platform platform = Platform.get();
for (Method method : service.getDeclaredMethods()) {
if (!platform.isDefaultMethod(method)) {
loadServiceMethod(method);
}
}
}
所以如果我们在Retrofit.Builder的validateEagerly参数被设置为true,我们在create方法执行的时候,就会遍历这个service的所有方法,由于platform.isDefaultMethod(method)在Android平台默认返回false,所以一定会执行 loadServiceMethod(method),也就是说如果设置validateEagerly=true,则Retrofit会把这个service接口的所有方法都load进来,也就说一次性全部导入。
ServiceMethod<?, ?> loadServiceMethod(Method method) {
ServiceMethod<?, ?> result = serviceMethodCache.get(method);
if (result != null) return result;
synchronized (serviceMethodCache) {
result = serviceMethodCache.get(method);
if (result == null) {
result = new ServiceMethod.Builder<>(this, method).build();
serviceMethodCache.put(method, result);
}
}
return result;
}
Builder(Retrofit retrofit, Method method) {
this.retrofit = retrofit;
this.method = method;
this.methodAnnotations = method.getAnnotations();
this.parameterTypes = method.getGenericParameterTypes();
this.parameterAnnotationsArray = method.getParameterAnnotations();
}
通过这个ServiceMethod.Builder的构造函数, ServiceMethod.Builder这个实例就获取了Retrofit对象和method对象,通过对method的解析,又获取了方法的注解,该方法参数的类型,该方法参数的注解。完成了ServiceMethod.Builder的初始化。
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);
}
这个方法里面我们重点讲解下几个部分
createCallAdapter主要是获取对应的CallAdapter的对象,那我们就详细分析下createCallAdapter()内部的代码。 看下代码
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 {
return (CallAdapter<T, R>) retrofit.callAdapter(returnType, annotations);
} catch (RuntimeException e) {
throw methodError(e, "Unable to create call adapter for %s", returnType);
}
}
callAdapter 主要负责把retrofit2.Call<R> 转化为T (注意和okhttp3.Call 区分开来) ,retrofit2.Call<R> 表示的是对一个Retrofit的接口方法的调用,也就是我们举得例子 Call<List<Contributor>> call = github.contributors("square", "retrofit")。通过上述代码我们知道createCallAdapter的内部其实是通过retrofit类中的callAdapter()方法来实现的。那我们再来看下retrofit类中的callAdapter()方法:
public CallAdapter<?, ?> callAdapter(Type returnType, Annotation[] annotations) {
return nextCallAdapter(null, returnType, annotations);
}
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++) {
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());
}
之前我们讲过,如果我们不addCallAdapterFactory()方法的话,那么在Retrofit.build()方法中,系统会添加一个平台默认的值:
List<CallAdapter.Factory> adapterFactories = new ArrayList<>(this.adapterFactories);
adapterFactories.add(platform.defaultCallAdapterFactory(callbackExecutor));
也就是没有设置,那么这里应该会添加平台默认的CallAdapterFactory,其实是ExecutorCallAdapterFactory类,。那我们再回到nextCallAdapter()中,在nextCallAdapter()方法中我们遍历adapterFactories,调动每一个CallAdapter.Factory的get()方法来获取一个CallAdapter。说白了,就是根据注解和返回值的类型,判断,如果你这个CallAdapter支持则返回对应的CallAdapter,如果不支持则返回null。
private Converter<ResponseBody, T> createResponseConverter() {
Annotation[] annotations = method.getAnnotations();
try {
return retrofit.responseBodyConverter(responseType, annotations);
} catch (RuntimeException e) {
throw methodError(e, "Unable to create converter for %s", responseType);
}
}
Converter<ResponseBody, T>主要负责把okhttp3.ResponseBody转化为类型T的对象。通过代码我们知道其实是调用retrofit类中的responseBodyConverter()方法,那我们来看下responseBodyConverter()方法里面的具体实现
public <T> Converter<ResponseBody, T> responseBodyConverter(Type type, Annotation[] annotations) {
return nextResponseBodyConverter(null, type, annotations);
}
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++) {
Converter<ResponseBody, ?> converter =
converterFactories.get(i).responseBodyConverter(type, annotations, this);
if (converter != null) {
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());
}
由于我们添加了
.addConverterFactory(GsonConverterFactory.create())
所以在Retrofit里面的converterFactories里面有两个Converter.Factory,一个是默认的BuiltInConverters,一个是GsonConverterFactory。 那我们再回到nextResponseBodyConverter()中,在nextResponseBodyConverter()方法中我们遍历converterFactories,调动每一个Converter.Factory的responseBodyConverter()方法来获取一个Converter。说白了,就是根据返回值类型、参数注解、方法注解来获取一个对应的Converter,如果你这个Converter.Factory支持则返回对应的Converter,则返回一个对应的Converter,如果不支持则返回null。在我们的demo中由于使用了GsonConverterFactory的get()方法返回的是GsonConverterFactory,而GsonConverterFactory的responseBodyConverter()返回到是GsonResponseBodyConverter实例。
看代码
for (Annotation annotation : methodAnnotations) {
parseMethodAnnotation(annotation);
}
通过遍历该方法的所有方法注解,调用parseMethodAnnotation来解析方法注解,那我们就来看下里面的具体执行
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;
}
}
Multipart大家不了解的看我前面的文章,这里面说下isMultipart 和 isFormEncoded是互斥的,所以后面解析方法参数的时候,遇到一些错误的操作,会直接抛异常,比如你方法注解使用了@Multipart,但是在参数那里使用了注解Field,由于是互斥的,所以会抛异常。
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).");
}
}
代码如下:
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);
}
那让我们看下parseParameter()方法是如何进行解析方法参数的
private ParameterHandler<?> parseParameter(
int p, Type parameterType, Annotation[] annotations) {
ParameterHandler<?> result = null;
for (Annotation annotation : annotations) {
ParameterHandler<?> annotationAction = parseParameterAnnotation(
p, parameterType, annotations, annotation);
if (annotationAction == null) {
continue;
}
if (result != null) {
throw parameterError(p, "Multiple Retrofit annotations found, only one allowed.");
}
result = annotationAction;
}
if (result == null) {
throw parameterError(p, "No Retrofit annotation found.");
}
return result;
}
parseParameter方法内部其实也是遍历这个参数的所有注解,然后通过调用 parseParameterAnnotation()方法来解析每一个注解。那么我们来看下 parseParameterAnnotation()方法内部的实现
private ParameterHandler<?> parseParameterAnnotation(
int p, Type type, Annotation[] annotations, Annotation annotation) {
if (annotation instanceof Url) {
if (gotUrl) {
throw parameterError(p, "Multiple @Url method annotations found.");
}
if (gotPath) {
throw parameterError(p, "@Path parameters may not be used with @Url.");
}
if (gotQuery) {
throw parameterError(p, "A @Url parameter must not come after a @Query");
}
if (relativeUrl != null) {
throw parameterError(p, "@Url cannot be used with @%s URL", httpMethod);
}
gotUrl = true;
if (type == HttpUrl.class
|| type == String.class
|| type == URI.class
|| (type instanceof Class && "android.net.Uri".equals(((Class<?>) type).getName()))) {
return new ParameterHandler.RelativeUrl();
} else {
throw parameterError(p,
"@Url must be okhttp3.HttpUrl, String, java.net.URI, or android.net.Uri type.");
}
} else if (annotation instanceof Path) {
if (gotQuery) {
throw parameterError(p, "A @Path parameter must not come after a @Query.");
}
if (gotUrl) {
throw parameterError(p, "@Path parameters may not be used with @Url.");
}
if (relativeUrl == null) {
throw parameterError(p, "@Path can only be used with relative url on @%s", httpMethod);
}
gotPath = true;
Path path = (Path) annotation;
String name = path.value();
validatePathName(p, name);
Converter<?, String> converter = retrofit.stringConverter(type, annotations);
return new ParameterHandler.Path<>(name, converter, path.encoded());
} else if (annotation instanceof Query) {
Query query = (Query) annotation;
String name = query.value();
boolean encoded = query.encoded();
Class<?> rawParameterType = Utils.getRawType(type);
gotQuery = true;
if (Iterable.class.isAssignableFrom(rawParameterType)) {
if (!(type instanceof ParameterizedType)) {
throw parameterError(p, rawParameterType.getSimpleName()
+ " must include generic type (e.g., "
+ rawParameterType.getSimpleName()
+ "<String>)");
}
ParameterizedType parameterizedType = (ParameterizedType) type;
Type iterableType = Utils.getParameterUpperBound(0, parameterizedType);
Converter<?, String> converter =
retrofit.stringConverter(iterableType, annotations);
return new ParameterHandler.Query<>(name, converter, encoded).iterable();
} else if (rawParameterType.isArray()) {
Class<?> arrayComponentType = boxIfPrimitive(rawParameterType.getComponentType());
Converter<?, String> converter =
retrofit.stringConverter(arrayComponentType, annotations);
return new ParameterHandler.Query<>(name, converter, encoded).array();
} else {
Converter<?, String> converter =
retrofit.stringConverter(type, annotations);
return new ParameterHandler.Query<>(name, converter, encoded);
}
} else if (annotation instanceof QueryName) {
QueryName query = (QueryName) annotation;
boolean encoded = query.encoded();
Class<?> rawParameterType = Utils.getRawType(type);
gotQuery = true;
if (Iterable.class.isAssignableFrom(rawParameterType)) {
if (!(type instanceof ParameterizedType)) {
throw parameterError(p, rawParameterType.getSimpleName()
+ " must include generic type (e.g., "
+ rawParameterType.getSimpleName()
+ "<String>)");
}
ParameterizedType parameterizedType = (ParameterizedType) type;
Type iterableType = Utils.getParameterUpperBound(0, parameterizedType);
Converter<?, String> converter =
retrofit.stringConverter(iterableType, annotations);
return new ParameterHandler.QueryName<>(converter, encoded).iterable();
} else if (rawParameterType.isArray()) {
Class<?> arrayComponentType = boxIfPrimitive(rawParameterType.getComponentType());
Converter<?, String> converter =
retrofit.stringConverter(arrayComponentType, annotations);
return new ParameterHandler.QueryName<>(converter, encoded).array();
} else {
Converter<?, String> converter =
retrofit.stringConverter(type, annotations);
return new ParameterHandler.QueryName<>(converter, encoded);
}
} else if (annotation instanceof QueryMap) {
Class<?> rawParameterType = Utils.getRawType(type);
if (!Map.class.isAssignableFrom(rawParameterType)) {
throw parameterError(p, "@QueryMap parameter type must be Map.");
}
Type mapType = Utils.getSupertype(type, rawParameterType, Map.class);
if (!(mapType instanceof ParameterizedType)) {
throw parameterError(p, "Map must include generic types (e.g., Map<String, String>)");
}
ParameterizedType parameterizedType = (ParameterizedType) mapType;
Type keyType = Utils.getParameterUpperBound(0, parameterizedType);
if (String.class != keyType) {
throw parameterError(p, "@QueryMap keys must be of type String: " + keyType);
}
Type valueType = Utils.getParameterUpperBound(1, parameterizedType);
Converter<?, String> valueConverter =
retrofit.stringConverter(valueType, annotations);
return new ParameterHandler.QueryMap<>(valueConverter, ((QueryMap) annotation).encoded());
} else if (annotation instanceof Header) {
Header header = (Header) annotation;
String name = header.value();
Class<?> rawParameterType = Utils.getRawType(type);
if (Iterable.class.isAssignableFrom(rawParameterType)) {
if (!(type instanceof ParameterizedType)) {
throw parameterError(p, rawParameterType.getSimpleName()
+ " must include generic type (e.g., "
+ rawParameterType.getSimpleName()
+ "<String>)");
}
ParameterizedType parameterizedType = (ParameterizedType) type;
Type iterableType = Utils.getParameterUpperBound(0, parameterizedType);
Converter<?, String> converter =
retrofit.stringConverter(iterableType, annotations);
return new ParameterHandler.Header<>(name, converter).iterable();
} else if (rawParameterType.isArray()) {
Class<?> arrayComponentType = boxIfPrimitive(rawParameterType.getComponentType());
Converter<?, String> converter =
retrofit.stringConverter(arrayComponentType, annotations);
return new ParameterHandler.Header<>(name, converter).array();
} else {
Converter<?, String> converter =
retrofit.stringConverter(type, annotations);
return new ParameterHandler.Header<>(name, converter);
}
} else if (annotation instanceof HeaderMap) {
Class<?> rawParameterType = Utils.getRawType(type);
if (!Map.class.isAssignableFrom(rawParameterType)) {
throw parameterError(p, "@HeaderMap parameter type must be Map.");
}
Type mapType = Utils.getSupertype(type, rawParameterType, Map.class);
if (!(mapType instanceof ParameterizedType)) {
throw parameterError(p, "Map must include generic types (e.g., Map<String, String>)");
}
ParameterizedType parameterizedType = (ParameterizedType) mapType;
Type keyType = Utils.getParameterUpperBound(0, parameterizedType);
if (String.class != keyType) {
throw parameterError(p, "@HeaderMap keys must be of type String: " + keyType);
}
Type valueType = Utils.getParameterUpperBound(1, parameterizedType);
Converter<?, String> valueConverter =
retrofit.stringConverter(valueType, annotations);
return new ParameterHandler.HeaderMap<>(valueConverter);
} else if (annotation instanceof Field) {
if (!isFormEncoded) {
throw parameterError(p, "@Field parameters can only be used with form encoding.");
}
Field field = (Field) annotation;
String name = field.value();
boolean encoded = field.encoded();
gotField = true;
Class<?> rawParameterType = Utils.getRawType(type);
if (Iterable.class.isAssignableFrom(rawParameterType)) {
if (!(type instanceof ParameterizedType)) {
throw parameterError(p, rawParameterType.getSimpleName()
+ " must include generic type (e.g., "
+ rawParameterType.getSimpleName()
+ "<String>)");
}
ParameterizedType parameterizedType = (ParameterizedType) type;
Type iterableType = Utils.getParameterUpperBound(0, parameterizedType);
Converter<?, String> converter =
retrofit.stringConverter(iterableType, annotations);
return new ParameterHandler.Field<>(name, converter, encoded).iterable();
} else if (rawParameterType.isArray()) {
Class<?> arrayComponentType = boxIfPrimitive(rawParameterType.getComponentType());
Converter<?, String> converter =
retrofit.stringConverter(arrayComponentType, annotations);
return new ParameterHandler.Field<>(name, converter, encoded).array();
} else {
Converter<?, String> converter =
retrofit.stringConverter(type, annotations);
return new ParameterHandler.Field<>(name, converter, encoded);
}
} else if (annotation instanceof FieldMap) {
if (!isFormEncoded) {
throw parameterError(p, "@FieldMap parameters can only be used with form encoding.");
}
Class<?> rawParameterType = Utils.getRawType(type);
if (!Map.class.isAssignableFrom(rawParameterType)) {
throw parameterError(p, "@FieldMap parameter type must be Map.");
}
Type mapType = Utils.getSupertype(type, rawParameterType, Map.class);
if (!(mapType instanceof ParameterizedType)) {
throw parameterError(p,
"Map must include generic types (e.g., Map<String, String>)");
}
ParameterizedType parameterizedType = (ParameterizedType) mapType;
Type keyType = Utils.getParameterUpperBound(0, parameterizedType);
if (String.class != keyType) {
throw parameterError(p, "@FieldMap keys must be of type String: " + keyType);
}
Type valueType = Utils.getParameterUpperBound(1, parameterizedType);
Converter<?, String> valueConverter =
retrofit.stringConverter(valueType, annotations);
gotField = true;
return new ParameterHandler.FieldMap<>(valueConverter, ((FieldMap) annotation).encoded());
} else if (annotation instanceof Part) {
if (!isMultipart) {
throw parameterError(p, "@Part parameters can only be used with multipart encoding.");
}
Part part = (Part) annotation;
gotPart = true;
String partName = part.value();
Class<?> rawParameterType = Utils.getRawType(type);
if (partName.isEmpty()) {
if (Iterable.class.isAssignableFrom(rawParameterType)) {
if (!(type instanceof ParameterizedType)) {
throw parameterError(p, rawParameterType.getSimpleName()
+ " must include generic type (e.g., "
+ rawParameterType.getSimpleName()
+ "<String>)");
}
ParameterizedType parameterizedType = (ParameterizedType) type;
Type iterableType = Utils.getParameterUpperBound(0, parameterizedType);
if (!MultipartBody.Part.class.isAssignableFrom(Utils.getRawType(iterableType))) {
throw parameterError(p,
"@Part annotation must supply a name or use MultipartBody.Part parameter type.");
}
return ParameterHandler.RawPart.INSTANCE.iterable();
} else if (rawParameterType.isArray()) {
Class<?> arrayComponentType = rawParameterType.getComponentType();
if (!MultipartBody.Part.class.isAssignableFrom(arrayComponentType)) {
throw parameterError(p,
"@Part annotation must supply a name or use MultipartBody.Part parameter type.");
}
return ParameterHandler.RawPart.INSTANCE.array();
} else if (MultipartBody.Part.class.isAssignableFrom(rawParameterType)) {
return ParameterHandler.RawPart.INSTANCE;
} else {
throw parameterError(p,
"@Part annotation must supply a name or use MultipartBody.Part parameter type.");
}
} else {
Headers headers =
Headers.of("Content-Disposition", "form-data; name=\"" + partName + "\"",
"Content-Transfer-Encoding", part.encoding());
if (Iterable.class.isAssignableFrom(rawParameterType)) {
if (!(type instanceof ParameterizedType)) {
throw parameterError(p, rawParameterType.getSimpleName()
+ " must include generic type (e.g., "
+ rawParameterType.getSimpleName()
+ "<String>)");
}
ParameterizedType parameterizedType = (ParameterizedType) type;
Type iterableType = Utils.getParameterUpperBound(0, parameterizedType);
if (MultipartBody.Part.class.isAssignableFrom(Utils.getRawType(iterableType))) {
throw parameterError(p, "@Part parameters using the MultipartBody.Part must not "
+ "include a part name in the annotation.");
}
Converter<?, RequestBody> converter =
retrofit.requestBodyConverter(iterableType, annotations, methodAnnotations);
return new ParameterHandler.Part<>(headers, converter).iterable();
} else if (rawParameterType.isArray()) {
Class<?> arrayComponentType = boxIfPrimitive(rawParameterType.getComponentType());
if (MultipartBody.Part.class.isAssignableFrom(arrayComponentType)) {
throw parameterError(p, "@Part parameters using the MultipartBody.Part must not "
+ "include a part name in the annotation.");
}
Converter<?, RequestBody> converter =
retrofit.requestBodyConverter(arrayComponentType, annotations, methodAnnotations);
return new ParameterHandler.Part<>(headers, converter).array();
} else if (MultipartBody.Part.class.isAssignableFrom(rawParameterType)) {
throw parameterError(p, "@Part parameters using the MultipartBody.Part must not "
+ "include a part name in the annotation.");
} else {
Converter<?, RequestBody> converter =
retrofit.requestBodyConverter(type, annotations, methodAnnotations);
return new ParameterHandler.Part<>(headers, converter);
}
}
} else if (annotation instanceof PartMap) {
if (!isMultipart) {
throw parameterError(p, "@PartMap parameters can only be used with multipart encoding.");
}
gotPart = true;
Class<?> rawParameterType = Utils.getRawType(type);
if (!Map.class.isAssignableFrom(rawParameterType)) {
throw parameterError(p, "@PartMap parameter type must be Map.");
}
Type mapType = Utils.getSupertype(type, rawParameterType, Map.class);
if (!(mapType instanceof ParameterizedType)) {
throw parameterError(p, "Map must include generic types (e.g., Map<String, String>)");
}
ParameterizedType parameterizedType = (ParameterizedType) mapType;
Type keyType = Utils.getParameterUpperBound(0, parameterizedType);
if (String.class != keyType) {
throw parameterError(p, "@PartMap keys must be of type String: " + keyType);
}
Type valueType = Utils.getParameterUpperBound(1, parameterizedType);
if (MultipartBody.Part.class.isAssignableFrom(Utils.getRawType(valueType))) {
throw parameterError(p, "@PartMap values cannot be MultipartBody.Part. "
+ "Use @Part List<Part> or a different value type instead.");
}
Converter<?, RequestBody> valueConverter =
retrofit.requestBodyConverter(valueType, annotations, methodAnnotations);
PartMap partMap = (PartMap) annotation;
return new ParameterHandler.PartMap<>(valueConverter, partMap.encoding());
} else if (annotation instanceof Body) {
if (isFormEncoded || isMultipart) {
throw parameterError(p,
"@Body parameters cannot be used with form or multi-part encoding.");
}
if (gotBody) {
throw parameterError(p, "Multiple @Body method annotations found.");
}
Converter<?, RequestBody> converter;
try {
converter = retrofit.requestBodyConverter(type, annotations, methodAnnotations);
} catch (RuntimeException e) {
// Wide exception range because factories are user code.
throw parameterError(e, p, "Unable to create @Body converter for %s", type);
}
gotBody = true;
return new ParameterHandler.Body<>(converter);
}
return null; // Not a Retrofit annotation.
}
通过上述代码我们知道,根据不同的注解来生成对应的不同的ParameterHandler的静态内部类对象,当然在生成不同的 ParameterHandler静态内部类对象之前,有一定的验证条件,保证内部逻辑清晰,不矛盾。
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.");
}
主要是把互斥的几种情况添加进去,如果出现则违反了原则,直接抛异常
return new ServiceMethod<>(this);
这时候我们用这个Builder作为参数new了一个ServiceMethod对象,并返回
ServiceMethod(Builder<R, T> builder) {
this.callFactory = builder.retrofit.callFactory();
this.callAdapter = builder.callAdapter;
this.baseUrl = builder.retrofit.baseUrl();
this.responseConverter = builder.responseConverter;
this.httpMethod = builder.httpMethod;
this.relativeUrl = builder.relativeUrl;
this.headers = builder.headers;
this.contentType = builder.contentType;
this.hasBody = builder.hasBody;
this.isFormEncoded = builder.isFormEncoded;
this.isMultipart = builder.isMultipart;
this.parameterHandlers = builder.parameterHandlers;
}
所以在ServiceMethod.Builder.build()方法里面主要是给Builder的各个属性赋值。保证这些属性最后正确地传递给ServiceMethod。在build()方法里面的流程如下:
整个上面流程如下图:
流程图.png
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 (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.callAdapter.adapt(okHttpCall);
}
});
大体流程如下:
PS:
简易的流程图如下:
image.png
执行请求主要分为两个部分,一个是执行同步请求,一个是执行异步请求 我们的demo是同步请求,我们先讲解同步请求,然后再讲解异步请求
同步代码如下:
List<Contributor> contributors = call.execute().body();
因为OkHttpCall是实现retrofit2.Call接口的具体实现类,所以 call.execute()实际调用是OkHttpCall的execute()方法
@Override public Response<T> execute() throws IOException {
okhttp3.Call call;
synchronized (this) {
if (executed) throw new IllegalStateException("Already executed.");
executed = true;
if (creationFailure != null) {
if (creationFailure instanceof IOException) {
throw (IOException) creationFailure;
} else {
throw (RuntimeException) creationFailure;
}
}
call = rawCall;
if (call == null) {
try {
call = rawCall = createRawCall();
} catch (IOException | RuntimeException e) {
creationFailure = e;
throw e;
}
}
}
if (canceled) {
call.cancel();
}
return parseResponse(call.execute());
}
然后是调用的createRawCall()l来获取一个okhttp3.Call,然后调用 parseResponse()来获取retrofit2.Response。
private okhttp3.Call createRawCall() throws IOException {
Request request = serviceMethod.toRequest(args);
okhttp3.Call call = serviceMethod.callFactory.newCall(request);
if (call == null) {
throw new NullPointerException("Call.Factory returned null.");
}
return call;
}
让我们看下ServiceMethod类的toRequest()方法
Request toRequest(Object... args) throws IOException {
RequestBuilder requestBuilder = new RequestBuilder(httpMethod, baseUrl, relativeUrl, headers,
contentType, hasBody, isFormEncoded, isMultipart);
@SuppressWarnings("unchecked")
ParameterHandler<Object>[] handlers = (ParameterHandler<Object>[]) parameterHandlers;
int argumentCount = args != null ? args.length : 0;
if (argumentCount != handlers.length) {
throw new IllegalArgumentException("Argument count (" + argumentCount
+ ") doesn't match expected count (" + handlers.length + ")");
}
for (int p = 0; p < argumentCount; p++) {
handlers[p].apply(requestBuilder, args[p]);
}
return requestBuilder.build();
}
通过上面代码我们知道
那我们来看下RequestBuilder的build()方法
Request build() {
HttpUrl url;
HttpUrl.Builder urlBuilder = this.urlBuilder;
if (urlBuilder != null) {
url = urlBuilder.build();
} else {
url = baseUrl.resolve(relativeUrl);
if (url == null) {
throw new IllegalArgumentException(
"Malformed URL. Base: " + baseUrl + ", Relative: " + relativeUrl);
}
}
RequestBody body = this.body;
if (body == null) {
// Try to pull from one of the builders.
if (formBuilder != null) {
body = formBuilder.build();
} else if (multipartBuilder != null) {
body = multipartBuilder.build();
} else if (hasBody) {
body = RequestBody.create(null, new byte[0]);
}
}
MediaType contentType = this.contentType;
if (contentType != null) {
if (body != null) {
body = new ContentTypeOverridingRequestBody(body, contentType);
} else {
requestBuilder.addHeader("Content-Type", contentType.toString());
}
}
return requestBuilder
.url(url)
.method(method, body)
.build();
}
通过上面代码我们知道build()方法流程如下:
注意事项:
这时候我们再回来看下OkHttpCall中的createRawCall()内部
Request request = serviceMethod.toRequest(args);
这个流程我们已经讲解完了。
okhttp3.Call call = serviceMethod.callFactory.newCall(request);
其实就是调用serviceMethod的callFactory对象的newCall(request)方法来获取一个okhttp3.Call对象,这个流程是在okhttp里面,我就不详细说了。
这时候我们又回到了OkHttpCall的execute()的里面,最后调用了parseResponse(call.execute()),截止到call.execute()我们一直都是在解析,构造请求,但是到call.execute(),我们正式发起HTTP请求了。parseResponse方法主要是解析响应体。我们一会再讲解。
call.enqueue(new Callback<List<Contributor>>() {
@Override
public void onResponse(Call<List<Contributor>> call, Response<List<Contributor>> response) {
List<Contributor> contributorList = response.body();
for (Contributor contributor : contributorList){
Log.d("login", contributor.getLogin());
Log.d("contributions", contributor.getContributions() + "");
}
}
@Override
public void onFailure(Call<List<Contributor>> call, Throwable t) {
}
});
因为OkHttpCall是实现retrofit2.Call接口的具体实现类,所以 call.enqueue()实际调用是OkHttpCall的enqueue()方法。那我们来看下OkHttpCall的enqueue()方法的源码
@Override public void enqueue(final Callback<T> 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<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();
}
}
});
}
其实内部也一样通过调用createRawCall()(createRawCall()方法内部的实现逻辑,我这里就不说了)方法来获取okhttp3.Call对象,然后调用okhttp3.Call的enqueue()方法来实现的。如果请求成功则调用parseResponse来解析响应体,解析过程中没有问题则调用callSuccess()方法,如果解析出现问题则调用callFailure()方法,其实callFailure()内调用的是callback.onFailure()方法;如果在请求过程中出现问题则也一样调用callback.onFailure()。
处理响应主要是调用Response<T> parseResponse(okhttp3.Response) 方法来解析响应体
Response<T> parseResponse(okhttp3.Response rawResponse) throws IOException {
ResponseBody rawBody = rawResponse.body();
rawResponse = rawResponse.newBuilder()
.body(new NoContentResponseBody(rawBody.contentType(), rawBody.contentLength()))
.build();
int code = rawResponse.code();
if (code < 200 || code >= 300) {
try {
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 {
T body = serviceMethod.toResponse(catchingBody);
return Response.success(body, rawResponse);
} catch (RuntimeException e) {
catchingBody.throwIfCaught();
throw e;
}
}
通过研究parseResponse代码,我们知道:
R toResponse(ResponseBody body) throws IOException {
return responseConverter.convert(body);
}
可见ServiceMethod类的parseResponse() 方法内部调用的是responseConverter.convert(body),responseConverter我们之前说过是ServiceMethod.Builder的build()方法中获取的通过调用createResponseConverter()来获取的,在上文我们知道这里的responseConverter是GsonResponseBodyConverter。那我们来看下GsonResponseBodyConverter的convert的内部实现
@Override public T convert(ResponseBody value) throws IOException {
JsonReader jsonReader = gson.newJsonReader(value.charStream());
try {
return adapter.read(jsonReader);
} finally {
value.close();
}
}
这样就实现了网络响应体的反序列化。 自此我们的ServiceMethod的toRespons()方法我们就解析完毕。
public static <T> Response<T> success(T body, okhttp3.Response rawResponse) {
if (rawResponse == null) throw new NullPointerException("rawResponse == null");
if (!rawResponse.isSuccessful()) {
throw new IllegalArgumentException("rawResponse must be successful response");
}
return new Response<>(rawResponse, body, null);
}
这里面很简单,就是作为参数new了一个retrofit2.Response对象,然我们来看下retrofit2.Response的构造函数
private Response(okhttp3.Response rawResponse, T body, ResponseBody errorBody) {
this.rawResponse = rawResponse;
this.body = body;
this.errorBody = errorBody;
}
至此,Response.success()方法我们分析关闭,至于Response. error()方法分析,请大家看我之前的文章。
同步流程图如下:
同步.png
我们再回过头来再来分析一下这张图 其实整个Retrofit的流程如下图:
retrofit.png
为了让大家更好的理解层级的结构,简单做了下面这张图,在层级上让大家更好的理解层级的结构
层级.png
如果加上大家自定义的interface和里面的方法,大体的结构如下:
retrofit结构.png
如果把上面的这张图立起来,就是下面这张图:
retrofit结构.png
看完这三张图,希望大家对Retrofit的理解能更深一步!