Fetch API主要暴露了三个接口一个方法。
- 三个接口
Request(资源请求)Response(请求的响应)Headers(Request/Response头部信息)
- 一个方法
fetch()(获取资源调用的方法- 更多介绍参考 Fetch API - Web API | MDN (mozilla.org)
一、 来看一段前端代码
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Test fetch</title>
<script>
function Test() {fetch("http://192.168.8.1/chfs/shared/test/format.1728106021784.json").then((response) => response.json()).then((data) => console.log(data));}
</script>
</head>
<body><button onclick="Test()">Test fetch</button></body>
</html>二、看c++代码对fetch response具体实现
1、services\network\public\mojom\fetch_api.mojom
// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.module network.mojom;// Corresponds to Fetch request's "mode" and "use-CORS-preflight flag":
// https://fetch.spec.whatwg.org/#concept-request-mode
//
// These values are persisted to logs. Entries should not be renumbered and
// numeric values should never be reused.
enum RequestMode {kSameOrigin = 0,kNoCors = 1,kCors = 2,kCorsWithForcedPreflight = 3,kNavigate = 4,// Add a new type here, then update "FetchRequestMode" in enums.xml.
};// Corresponds to Fetch request's "destination":
// https://fetch.spec.whatwg.org/#concept-request-destination
//
// These values are persisted to logs. Entries should not be renumbered and
// numeric values should never be reused.
enum RequestDestination {kEmpty = 0,kAudio = 1,kAudioWorklet = 2,// kDocument is for a main resource request in a main frame, or a Portal.kDocument = 3,kEmbed = 4,kFont = 5,kFrame = 6,kIframe = 7,kImage = 8,kManifest = 9,kObject = 10,kPaintWorklet = 11,kReport = 12,kScript = 13,kServiceWorker = 14,kSharedWorker = 15,kStyle = 16,kTrack = 17,kVideo = 18,// kWebBundle represents a request for a WebBundle. A <script> element whose// type is "webbundle" uses this destination.//// e.g. <script type=webbundle> { "source": "foo.wbn", ... } </script>//// Fetch specifiction does not define this destination yet.// Tracking issue: https://github.com/whatwg/fetch/issues/1120kWebBundle = 19,kWorker = 20,kXslt = 21,// kFencedframe represents a main resource request in a fenced frame. A// <fencedframe> element uses this destination.//// e.g. <fencedframe src="example.com"></fencedframe>//// Fenced Frame is not standardized yet. See// https://github.com/shivanigithub/fenced-frame for the explainer and// crbug.com/1123606 for the implementation.kFencedframe = 22,// Requests from the federated credential management API,// https://fedidcg.github.io/FedCM/kWebIdentity = 23,// Requests for compression dictionarykDictionary = 24,// Requests for speculation rules.// https://wicg.github.io/nav-speculation/speculation-rules.htmlkSpeculationRules = 25,
};// Corresponds to Fetch request's "redirect mode":
// https://fetch.spec.whatwg.org/#concept-request-redirect-mode
enum RedirectMode {kFollow,kError,kManual,
};// Corresponds to Fetch request's "credentials mode":
// https://fetch.spec.whatwg.org/#concept-request-credentials-mode
enum CredentialsMode {// TODO(https://crbug.com/775438): Due to a bug, this does not properly// correspond to Fetch's "credentials mode", in that client certificates will// be sent is available, or the handshake will be aborted in order to allow// selecting a client cert. The correct behavior is to omit all client certs// and continue the handshake without sending one if requested.kOmit,kSameOrigin,kInclude,// TODO(https://crbug.com/775438): This works around kOmit not doing the// spec-defined behavior. This is a temporary workaround that explicitly// indicates the caller wants the spec-defined behavior. It's named as such// because this should be only temporary, until kOmit is fixed.kOmitBug_775438_Workaround
};// Corresponds to response types from the Fetch spec:
// https://fetch.spec.whatwg.org/#concept-response-type
//
// These values are persisted to logs. Entries should not be renumbered and
// numeric values should never be reused.
enum FetchResponseType {kBasic = 0,kCors = 1,kDefault = 2,kError = 3,kOpaque = 4,kOpaqueRedirect = 5,// Add a new type here, then update "FetchResponseType" in enums.xml.
};// Indicates the source of a response.
// This represents the source of the outmost response of a request.
// This is used only for histograms and isn't web-exposed.
enum FetchResponseSource {// The source is unspecified: e.g. "new Response('hi')" or a response from// a service worker.kUnspecified,// The response came from network: e.g. "fetch(req)".kNetwork,// The response came from HttpCache: e.g. "fetch(req)" and there is an entry// in HttpCache.kHttpCache,// The response came from CacheStorage: e.g. "cache.match(req)" in a fetch// event handler.kCacheStorage,
};
2、在third_party\blink\renderer\core\fetch\global_fetch.h 定义了Fetch函数具体实现
// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_FETCH_GLOBAL_FETCH_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_FETCH_GLOBAL_FETCH_H_#include "third_party/blink/renderer/bindings/core/v8/script_promise.h"
#include "third_party/blink/renderer/bindings/core/v8/v8_typedefs.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/fetch/request.h"namespace blink {class ExceptionState;
class LocalDOMWindow;
class NavigatorBase;
class RequestInit;
class DeferredRequestInit;
class ScriptState;
class WorkerGlobalScope;
class FetchLaterResult;class CORE_EXPORT GlobalFetch {STATIC_ONLY(GlobalFetch);public:class CORE_EXPORT ScopedFetcher : public GarbageCollectedMixin {public:virtual ~ScopedFetcher();virtual ScriptPromise Fetch(ScriptState*,const V8RequestInfo*,const RequestInit*,ExceptionState&) = 0;virtual FetchLaterResult* FetchLater(ScriptState*,const V8RequestInfo*,const DeferredRequestInit*,ExceptionState&);// Returns the number of fetch() method calls in the associated execution// context. This is used for metrics.virtual uint32_t FetchCount() const = 0;static ScopedFetcher* From(LocalDOMWindow&);static ScopedFetcher* From(WorkerGlobalScope&);static ScopedFetcher* From(NavigatorBase& navigator);void Trace(Visitor*) const override;};static ScriptPromise fetch(ScriptState* script_state,LocalDOMWindow& window,const V8RequestInfo* input,const RequestInit* init,ExceptionState& exception_state);static ScriptPromise fetch(ScriptState* script_state,WorkerGlobalScope& worker,const V8RequestInfo* input,const RequestInit* init,ExceptionState& exception_state);static FetchLaterResult* fetchLater(ScriptState* script_state,LocalDOMWindow& window,const V8RequestInfo* input,const DeferredRequestInit* init,ExceptionState& exception_state);
};} // namespace blink#endif // THIRD_PARTY_BLINK_RENDERER_CORE_FETCH_GLOBAL_FETCH_H_
3、Fetch 管理类 third_party\blink\renderer\core\fetch\fetch_manager.h
4、前端接口 Request(资源请求) third_party\blink\renderer\core\fetch\headers.idl
// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.// https://fetch.spec.whatwg.org/#typedefdef-headersinittypedef (sequence<sequence<ByteString>> or record<ByteString, ByteString>) HeadersInit;// https://fetch.spec.whatwg.org/#headers-class[Exposed=(Window,Worker)
] interface Headers {[CallWith=ScriptState, RaisesException] constructor(optional HeadersInit init);[CallWith=ScriptState, RaisesException] void append(ByteString name, ByteString value);[CallWith=ScriptState, ImplementedAs=remove, RaisesException] void delete(ByteString key);[RaisesException] ByteString? get(ByteString key);sequence<ByteString> getSetCookie();[RaisesException] boolean has(ByteString key);[CallWith=ScriptState, RaisesException] void set(ByteString key, ByteString value);iterable<ByteString, ByteString>;
};
对应实现c++类：
third_party\blink\renderer\core\fetch\headers.h
third_party\blink\renderer\core\fetch\headers.cc
// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_FETCH_HEADERS_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_FETCH_HEADERS_H_#include "third_party/blink/renderer/bindings/core/v8/iterable.h"
#include "third_party/blink/renderer/bindings/core/v8/v8_sync_iterator_headers.h"
#include "third_party/blink/renderer/bindings/core/v8/v8_typedefs.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/fetch/fetch_header_list.h"
#include "third_party/blink/renderer/platform/bindings/script_wrappable.h"
#include "third_party/blink/renderer/platform/heap/collection_support/heap_hash_set.h"
#include "third_party/blink/renderer/platform/wtf/forward.h"namespace blink {class ExceptionState;
class ScriptState;// http://fetch.spec.whatwg.org/#headers-class
class CORE_EXPORT Headers final : public ScriptWrappable,public PairSyncIterable<Headers> {DEFINE_WRAPPERTYPEINFO();public:enum Guard {kImmutableGuard,kRequestGuard,kRequestNoCorsGuard,kResponseGuard,kNoneGuard};static Headers* Create(ScriptState* script_state,ExceptionState& exception_state);static Headers* Create(ScriptState* script_state,const V8HeadersInit* init,ExceptionState& exception_state);// Shares the FetchHeaderList. Called when creating a Request or Response.static Headers* Create(FetchHeaderList*);Headers();// Shares the FetchHeaderList. Called when creating a Request or Response.explicit Headers(FetchHeaderList*);Headers* Clone() const;// Headers.idl implementation.void append(ScriptState* script_state,const String& name,const String& value,ExceptionState&);void remove(ScriptState* script_state, const String& key, ExceptionState&);String get(const String& key, ExceptionState&);Vector<String> getSetCookie();bool has(const String& key, ExceptionState&);void set(ScriptState* script_state,const String& key,const String& value,ExceptionState&);void SetGuard(Guard guard) { guard_ = guard; }Guard GetGuard() const { return guard_; }// These methods should only be called when size() would return 0.void FillWith(ScriptState* script_state, const Headers*, ExceptionState&);void FillWith(ScriptState* script_state,const V8HeadersInit* init,ExceptionState& exception_state);// https://fetch.spec.whatwg.org/#concept-headers-remove-privileged-no-cors-request-headersvoid RemovePrivilegedNoCorsRequestHeaders();FetchHeaderList* HeaderList() const { return header_list_.Get(); }void Trace(Visitor*) const override;private:class HeadersIterationSource final: public PairSyncIterable<Headers>::IterationSource {public:explicit HeadersIterationSource(Headers* headers);~HeadersIterationSource() override;bool FetchNextItem(ScriptState* script_state,String& key,String& value,ExceptionState& exception) override;void Trace(Visitor*) const override;void ResetHeaderList();private:// https://webidl.spec.whatwg.org/#dfn-value-pairs-to-iterate-overVector<std::pair<String, String>> headers_list_;// https://webidl.spec.whatwg.org/#default-iterator-object-indexwtf_size_t current_ = 0;Member<Headers> headers_;};// These methods should only be called when size() would return 0.void FillWith(ScriptState* script_state,const Vector<Vector<String>>&,ExceptionState&);void FillWith(ScriptState* script_state,const Vector<std::pair<String, String>>&,ExceptionState&);Member<FetchHeaderList> header_list_;Guard guard_;IterationSource* CreateIterationSource(ScriptState*,ExceptionState&) override;HeapHashSet<WeakMember<HeadersIterationSource>> iterators_;
};} // namespace blink#endif // THIRD_PARTY_BLINK_RENDERER_CORE_FETCH_HEADERS_H_
5、Response(请求的响应) third_party\blink\renderer\core\fetch\response.idl
// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.// https://fetch.spec.whatwg.org/#response-classenum ResponseType { "basic", "cors", "default", "error", "opaque", "opaqueredirect" };[Exposed=(Window,Worker)
] interface Response {// TODO(yhirano): We use "any" for body because the IDL processor doesn't// recognize ReadableStream implemented with V8 extras. Fix it.[CallWith=ScriptState, RaisesException] constructor(optional any body, optional ResponseInit init = {});[CallWith=ScriptState, NewObject] static Response error();[CallWith=ScriptState, NewObject, RaisesException] static Response redirect(USVString url, optional unsigned short status = 302);[CallWith=ScriptState, NewObject, RaisesException, ImplementedAs=staticJson] static Response json(any data, optional ResponseInit init = {});readonly attribute ResponseType type;readonly attribute USVString url;readonly attribute boolean redirected;readonly attribute unsigned short status;readonly attribute boolean ok;readonly attribute ByteString statusText;[SameObject] readonly attribute Headers headers;[RaisesException, CallWith=ScriptState, NewObject] Response clone();[Affects=Everything, MeasureAs=FetchBodyStream] readonly attribute ReadableStream? body;
};Response includes Body;
对应response接口c++实现类：
third_party\blink\renderer\core\fetch\response.h
third_party\blink\renderer\core\fetch\response.cc
// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_FETCH_RESPONSE_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_FETCH_RESPONSE_H_#include "services/network/public/mojom/fetch_api.mojom-blink.h"
#include "third_party/blink/public/mojom/fetch/fetch_api_response.mojom-blink-forward.h"
#include "third_party/blink/renderer/bindings/core/v8/dictionary.h"
#include "third_party/blink/renderer/bindings/core/v8/script_value.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/fetch/body.h"
#include "third_party/blink/renderer/core/fetch/body_stream_buffer.h"
#include "third_party/blink/renderer/core/fetch/fetch_response_data.h"
#include "third_party/blink/renderer/core/fetch/headers.h"
#include "third_party/blink/renderer/platform/bindings/script_wrappable.h"
#include "third_party/blink/renderer/platform/blob/blob_data.h"
#include "third_party/blink/renderer/platform/heap/garbage_collected.h"
#include "third_party/blink/renderer/platform/wtf/text/wtf_string.h"
#include "third_party/blink/renderer/platform/wtf/vector.h"namespace blink {class ExceptionState;
class ResponseInit;
class ScriptState;class CORE_EXPORT Response final : public ScriptWrappable, public Body {DEFINE_WRAPPERTYPEINFO();public:// These "create" function which takes a ScriptState* must be called with// entering an appropriate V8 context.// From Response.idl:static Response* Create(ScriptState*, ExceptionState&);static Response* Create(ScriptState*,ScriptValue body,const ResponseInit*,ExceptionState&);static Response* Create(ScriptState*,BodyStreamBuffer*,const String& content_type,const ResponseInit*,ExceptionState&);static Response* Create(ExecutionContext*, FetchResponseData*);static Response* Create(ScriptState*, mojom::blink::FetchAPIResponse&);static Response* CreateClone(const Response&);static Response* error(ScriptState*);static Response* redirect(ScriptState*,const String& url,uint16_t status,ExceptionState&);static Response* staticJson(ScriptState*,ScriptValue data,const ResponseInit*,ExceptionState&);static FetchResponseData* CreateUnfilteredFetchResponseDataWithoutBody(ScriptState*,mojom::blink::FetchAPIResponse&);static FetchResponseData* FilterResponseData(network::mojom::FetchResponseType response_type,FetchResponseData* response,WTF::Vector<WTF::String>& headers);explicit Response(ExecutionContext*);Response(ExecutionContext*, FetchResponseData*);Response(ExecutionContext*, FetchResponseData*, Headers*);Response(const Response&) = delete;Response& operator=(const Response&) = delete;const FetchResponseData* GetResponse() const { return response_.Get(); }// From Response.idl:String type() const;String url() const;bool redirected() const;uint16_t status() const;bool ok() const;String statusText() const;Headers* headers() const;// From Response.idl:// This function must be called with entering an appropriate V8 context.Response* clone(ScriptState*, ExceptionState&);// Does not contain the blob response body or any side data blob.// |request_url| is the current request URL that resulted in the response. It// is needed to process some response headers (e.g. CSP).// TODO(lfg, kinuko): The FetchResponseData::url_list_ should include the// request URL per step 9 in Main Fetch// https://fetch.spec.whatwg.org/#main-fetch. Just fixing it might break the// logic in ResourceMultiBufferDataProvider, please see// https://chromium-review.googlesource.com/c/1366464 for more details.mojom::blink::FetchAPIResponsePtr PopulateFetchAPIResponse(const KURL& request_url);bool HasBody() const;BodyStreamBuffer* BodyBuffer() override { return response_->Buffer(); }// Returns the BodyStreamBuffer of |m_response|. This method doesn't check// the internal response of |m_response| even if |m_response| has it.const BodyStreamBuffer* BodyBuffer() const override {return response_->Buffer();}// Returns the BodyStreamBuffer of the internal response of |m_response| if// any. Otherwise, returns one of |m_response|.BodyStreamBuffer* InternalBodyBuffer() { return response_->InternalBuffer(); }const BodyStreamBuffer* InternalBodyBuffer() const {return response_->InternalBuffer();}bool IsBodyUsed() const override;String ContentType() const override;String MimeType() const override;String InternalMIMEType() const;const Vector<KURL>& InternalURLList() const;FetchHeaderList* InternalHeaderList() const;void Trace(Visitor*) const override;private:const Member<FetchResponseData> response_;const Member<Headers> headers_;
};} // namespace blink#endif // THIRD_PARTY_BLINK_RENDERER_CORE_FETCH_RESPONSE_H_
1）、 Response body对应实现类：third_party\blink\renderer\core\fetch\body.idl
// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.// https://fetch.spec.whatwg.org/#body[ActiveScriptWrappable
] interface mixin Body {readonly attribute boolean bodyUsed;[CallWith=ScriptState, NewObject, RaisesException] Promise<ArrayBuffer> arrayBuffer();[CallWith=ScriptState, NewObject, RaisesException] Promise<Blob> blob();[CallWith=ScriptState, NewObject, RaisesException] Promise<FormData> formData();[CallWith=ScriptState, NewObject, RaisesException] Promise<any> json();[CallWith=ScriptState, NewObject, RaisesException] Promise<USVString> text();// body attribute is defined in sub-interfaces, because the IDL processor// cannot deal with attribute inheritance with runtime enabled flag.// [RuntimeEnabled=ExperimentalStream] readonly attribute ReadableByteStream body;
};
third_party\blink\renderer\core\fetch\body.h
third_party\blink\renderer\core\fetch\body.cc
// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_FETCH_BODY_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_FETCH_BODY_H_#include "third_party/blink/renderer/bindings/core/v8/script_promise.h"
#include "third_party/blink/renderer/bindings/core/v8/script_value.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/execution_context/execution_context_lifecycle_observer.h"
#include "third_party/blink/renderer/platform/bindings/script_wrappable.h"
#include "third_party/blink/renderer/platform/wtf/text/wtf_string.h"namespace blink {class BodyStreamBuffer;
class ExceptionState;
class ExecutionContext;
class ReadableStream;
class ScriptPromiseResolver;
class ScriptState;// This class represents Body mix-in defined in the fetch spec
// https://fetch.spec.whatwg.org/#body-mixin.
//
// Note: This class has body stream and its predicate whereas in the current
// spec only Response has it and Request has a byte stream defined in the
// Encoding spec. The spec should be fixed shortly to be aligned with this
// implementation.
class CORE_EXPORT Body : public ExecutionContextClient {public:explicit Body(ExecutionContext*);Body(const Body&) = delete;Body& operator=(const Body&) = delete;ScriptPromise arrayBuffer(ScriptState*, ExceptionState&);ScriptPromise blob(ScriptState*, ExceptionState&);ScriptPromise formData(ScriptState*, ExceptionState&);ScriptPromise json(ScriptState*, ExceptionState&);ScriptPromise text(ScriptState*, ExceptionState&);ReadableStream* body();virtual BodyStreamBuffer* BodyBuffer() = 0;virtual const BodyStreamBuffer* BodyBuffer() const = 0;// This should only be called from the generated bindings. All other code// should use IsBodyUsed() instead.bool bodyUsed() const { return IsBodyUsed(); }// True if the body has been read from.virtual bool IsBodyUsed() const;// True if the body is locked.bool IsBodyLocked() const;private:// TODO(e_hakkinen): Fix |MimeType()| to always contain parameters and// remove |ContentType()|.virtual String ContentType() const = 0;virtual String MimeType() const = 0;// Body consumption algorithms will reject with a TypeError in a number of// error conditions. This method wraps those up into one call which throws// an exception if consumption cannot proceed. The caller must check// |exception_state| on return.void RejectInvalidConsumption(ExceptionState& exception_state) const;// The parts of LoadAndConvertBody() that do not depend on the template// parameters are split into this method to reduce binary size. Returns a// freshly-created ScriptPromiseResolver* on success, or nullptr on error. On// error, LoadAndConvertBody() must not continue.ScriptPromiseResolver* PrepareToLoadBody(ScriptState*, ExceptionState&);// Common implementation for body-reading accessors. To maximise performance// at the cost of code size, this is templated on the types of the lambdas// that are passed in.template <class Consumer,typename CreateLoaderFunction,typename OnNoBodyFunction>ScriptPromise LoadAndConvertBody(ScriptState*,CreateLoaderFunction,OnNoBodyFunction,ExceptionState&);
};} // namespace blink#endif // THIRD_PARTY_BLINK_RENDERER_CORE_FETCH_BODY_H_
6、Headers(Request/Response头部信息) third_party\blink\renderer\core\fetch\headers.idl
// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.// https://fetch.spec.whatwg.org/#typedefdef-headersinittypedef (sequence<sequence<ByteString>> or record<ByteString, ByteString>) HeadersInit;// https://fetch.spec.whatwg.org/#headers-class[Exposed=(Window,Worker)
] interface Headers {[CallWith=ScriptState, RaisesException] constructor(optional HeadersInit init);[CallWith=ScriptState, RaisesException] void append(ByteString name, ByteString value);[CallWith=ScriptState, ImplementedAs=remove, RaisesException] void delete(ByteString key);[RaisesException] ByteString? get(ByteString key);sequence<ByteString> getSetCookie();[RaisesException] boolean has(ByteString key);[CallWith=ScriptState, RaisesException] void set(ByteString key, ByteString value);iterable<ByteString, ByteString>;
};
至此定义实现已经介绍完毕，在下一篇看下调用堆栈：
Chromium 中JavaScript Fetch API接口c++代码实现（二）-CSDN博客
