JavaScript Fetch API 接口在 Chromium c++ 代码中的实现（二）

最编程 2024-10-06 18:36:48

...

3、点击页面测试按钮调转到c++代码

F:\code\google\src\third_party\blink\renderer\core\fetch\fetch_manager.cc

ScriptPromise FetchManager::Fetch(ScriptState* script_state,
                                  FetchRequestData* request,
                                  AbortSignal* signal,
                                  ExceptionState& exception_state) {
  DCHECK(signal);
  if (signal->aborted()) {
    exception_state.RethrowV8Exception(signal->reason(script_state).V8Value());
    return ScriptPromise();
  }

  request->SetDestination(network::mojom::RequestDestination::kEmpty);

  auto* resolver = MakeGarbageCollected<ScriptPromiseResolver>(
      script_state, exception_state.GetContext());
  ScriptPromise promise = resolver->Promise();

  auto* loader = MakeGarbageCollected<Loader>(
      GetExecutionContext(), this, resolver, request, script_state, signal);
  loaders_.insert(loader);
  // TODO(ricea): Reject the Response body with AbortError, not TypeError.
  loader->Start(exception_state);
  return promise;
}

可以看到已经进入fetch函数

4、response响应堆栈：

third_party\blink\renderer\platform\loader\fetch\url_loader\background_url_loader.cc

5、third_party\blink\renderer\platform\loader\fetch\resource_loader.h 资源加载响应

\third_party\blink\renderer\platform\loader\fetch\resource_loader.cc

//通知body 响应response.json()函数

  // FrameType never changes during the lifetime of a request.
  if (auto* observer = fetcher_->GetResourceLoadObserver()) {
    ResourceRequest request_for_obserber(initial_request);
    // TODO(yoichio): Have DidReceiveResponse take a ResourceResponseHead, not
    // ResourceRequest.


    observer->DidReceiveResponse(
        resource_->InspectorId(), request_for_obserber, response, resource_,
        ResourceLoadObserver::ResponseSource::kNotFromMemoryCache);
  }

6、src\out\Debug\gen\third_party\blink\renderer\bindings\core\v8\v8_response.cc

void JsonOperationCallback(const v8::FunctionCallbackInfo<v8::Value>& info) {
  RUNTIME_CALL_TIMER_SCOPE_DISABLED_BY_DEFAULT(info.GetIsolate(), "Blink_Response_json");
BLINK_BINDINGS_TRACE_EVENT("Response.json");

// Promise returning function: Convert a TypeError to a reject promise.
v8::Isolate* isolate = info.GetIsolate();
v8::Local<v8::Object> v8_receiver = info.This();
const ExceptionContextType exception_context_type = ExceptionContextType::kOperationInvoke;
const char* const class_like_name = "Response";
const char* const property_name = "json";
ExceptionState exception_state(isolate, exception_context_type, class_like_name, property_name);
ExceptionToRejectPromiseScope reject_promise_scope(info, exception_state);
if (!V8Response::HasInstance(isolate, v8_receiver)) {
  exception_state.ThrowTypeError("Illegal invocation");
return;
}







Response* blink_receiver = V8Response::ToWrappableUnsafe(isolate, v8_receiver);
v8::Local<v8::Context> receiver_context = v8_receiver->GetCreationContextChecked();
ScriptState* receiver_script_state = ScriptState::From(receiver_context);
ScriptState* script_state = receiver_script_state;
auto&& return_value = blink_receiver->json(script_state, exception_state);
if (UNLIKELY(exception_state.HadException())) {
  return;
}
bindings::V8SetReturnValue(info, return_value);
}

7、src\third_party\blink\renderer\core\fetch\body.cc

Response.json 响应

ScriptPromise Body::json(ScriptState* script_state,
                         ExceptionState& exception_state) {
  auto on_no_body = [script_state](ScriptPromiseResolver* resolver) {
    resolver->Reject(V8ThrowException::CreateSyntaxError(
        script_state->GetIsolate(), "Unexpected end of input"));
  };
  return LoadAndConvertBody<BodyJsonConsumer>(
      script_state, &CreateLoaderAsStringWithUTF8Decode, on_no_body,
      exception_state);
}

8、最后返回前端效果如下：

至于其他细节，自行查看代码吧，用户还可以通过此处源码自行修改前端的一些请求数据。

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