Retrofit自定义请求参数注解的实现教程

@GET("transporter/info")
Flowable getTransporterInfo(@Query("uid") long id);

@POST("transporter/update")
Flowable changBind(@Body Map params);

public interface GitHubService {
 @GET("users/{user}/repos")
 Call> listRepos(@Path("user") String user);
}

@FormUrlEncoded
@POST("user/edit")
Call updateUser(@Field("first_name") String first, @Field("last_name") String last);

Builder(Retrofit retrofit, Method method) {
 this.retrofit = retrofit;
 this.method = method;
 this.methodAnnotations = method.getAnnotations();
 this.parameterTypes = method.getGenericParameterTypes();
 this.parameterAnnotationsArray = method.getParameterAnnotations();
}

//省略了部分代码...

public ServiceMethod build() {
 //1. 解析方法上的注解
 for (Annotation annotation : methodAnnotations) {
 parseMethodAnnotation(annotation);
 }

 int parameterCount = parameterAnnotationsArray.length;
 parameterHandlers = new ParameterHandler>[parameterCount];
 for (int p = 0; p (this);
}

if (annotation instanceof GET) {
 parseHttpMethodAndPath("GET", ((GET) annotation).value(), false);
}else if (annotation instanceof POST) {
 parseHttpMethodAndPath("POST", ((POST) annotation).value(), true);
} 

private void parseHttpMethodAndPath(String httpMethod, String value, boolean hasBody) {
 this.httpMethod = httpMethod;
 this.hasBody = hasBody;
 // Get the relative URL path and existing query string, if present.
 // ...
}

private ParameterHandler> parseParameter(
 int p, Type parameterType, Annotation[] annotations) {
 ParameterHandler> result = null;
 for (Annotation annotation : annotations) {
 ParameterHandler> annotationAction = parseParameterAnnotation(
 p, parameterType, annotations, annotation);
 }
 // 省略部分代码...
 return result;
}

else if (annotation instanceof Field) {
 Field field = (Field) annotation;
 String name = field.value();
 boolean encoded = field.encoded();

 gotField = true;
 Converter, String> converter = retrofit.stringConverter(type, annotations);
 return new ParameterHandler.Field(name, converter, encoded);

}

//省略部分代码
static final class Field extends ParameterHandler {
 private final String name;
 private final Converter valueConverter;
 private final boolean encoded;

 //构造函数...

 @Override
 void apply(RequestBuilder builder, @Nullable T value) throws IOException {
 String fieldValue = valueConverter.convert(value);
 builder.addFormField(name, fieldValue, encoded);
 }
}

else if (annotation instanceof Body) {
 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);
}

 static final class Body extends ParameterHandler {
 private final Converter converter;

 Body(Converter converter) {
 this.converter = converter;
 }

 @Override
 void apply(RequestBuilder builder, @Nullable T value) {
 RequestBody body;
 try {
 body = converter.convert(value);
 } catch (IOException e) {
 throw new RuntimeException("Unable to convert " + value + " to RequestBody", e);
 }
 builder.setBody(body);
 }
}

//省略部分代码...
@Override
public Response execute() throws IOException {
 okhttp3.Call call;

 synchronized (this) {
 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());
}

/**
 * 根据方法参数创建一个 HTTP 请求
 */
Request toRequest(@Nullable Object... args) throws IOException {
 RequestBuilder requestBuilder = new RequestBuilder(httpMethod, baseUrl, relativeUrl, headers, contentType, hasBody, isFormEncoded, isMultipart);
 ParameterHandler

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 is absent, make an empty body.
 body = RequestBody.create(null, new byte[0]);
 }
}

public @interface BodyQuery {
 /**
 * The query parameter name.
 */
 String value();

 /**
 * Specifies whether the parameter {@linkplain #value() name} and value are already URL encoded.
 */
 boolean encoded() default false;
}

static final class BodyQuery extends ParameterHandler {
 private final String name;
 private final Converter valueConverter;

 BodyQuery(String name, Converter valueConverter) {
 this.name = checkNotNull(name, "name == null");
 this.valueConverter = valueConverter;
 }

 @Override
 void apply(RequestBuilder builder, @Nullable T value) throws IOException {
 String fieldValue = valueConverter.convert(value);
 builder.addBodyQueryParams(name, fieldValue);
 }
}

// 在 RequestBuilder 中新增的方法
void addBodyQueryParams(String name, String value) {
 bodyQueryMaps.put(name, value);
}

else if (annotation instanceof BodyQuery) {
 BodyQuery field = (BodyQuery) annotation;
 String name = field.value();
 hasBodyQuery = true;

 Converter, String> converter = retrofit.stringConverter(type, annotations);
 return new ParameterHandler.BodyQuery(name, converter);
}

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 (hasBodyQuery) {
 body = RequestBody.create(MediaType.parse("application/json; charset=UTF-8"), JSON.toJSONBytes(this.bodyQueryMaps));

 } else if (hasBody) {
 // Body is absent, make an empty body.
 body = RequestBody.create(null, new byte[0]);
 }
}

@Test
public void simpleBodyQuery(){
 class Example{
 @POST("/foo")
 Call method(@BodyQuery("A") String foo,@BodyQuery("B") String ping){
  return null;
 }
 }
 Request request = buildRequest(Example.class,"hello","world");
 assertBody(request.body(), "{"A":"hello","B":"world"}");
}