一、源码实现分析
-
axios
源码目录结构,如下所示:├── /dist/ # 项目输出目录 ├── /lib/ # 项目源码目录 │ ├── /adapters/ # 定义请求的适配器 xhr、http │ │ ├── http.js # 实现http适配器(包装http包) │ │ └── xhr.js # 实现xhr适配器(包装xhr对象) │ ├── /cancel/ # 定义取消功能 │ ├── /core/ # 一些核心功能 │ │ ├── Axios.js # axios的核心主类 │ │ ├── dispatchRequest.js # 用来调用http请求适配器方法发送请求的函数 │ │ ├── InterceptorManager.js # 拦截器的管理器 │ │ └── settle.js # 根据http响应状态,改变Promise的状态 │ ├── /helpers/ # 一些辅助方法 │ ├── axios.js # 对外暴露接口 │ ├── defaults.js # axios的默认配置 │ └── utils.js # 公用工具 ├── package.json # 项目信息 ├── index.d.ts # 配置TypeScript的声明文件 └── index.js # 入口文件
-
axios
与Axios
的关系,如下所示:
- 从语法上来说:
axios
不是Axios
的实例 - 从功能上来说:
axios
是Axios
的实例 axios
函数对应的是Axios.prototype.request
方法通过bind(Axiox的实例)
产生的函数axios
作为对象有Axios
原型对象上的所有方法, 有Axios
对象上所有属性axios
有Axios
原型上的所有发特定类型请求的方法:get()/post()/put()/delete()
axios
有Axios
的实例上的所有属性:defaults/interceptors
,后面又添加了create()/CancelToken()/all()
instance
与axios
的区别? 如下所示:
- 相同点:
- 都是一个能发任意请求的函数:
request(config)
- 都有发特定请求的各种方法:
get()/post()/put()/delete()
- 都有默认配置和拦截器的属性:
defaults/interceptors
- 都是一个能发任意请求的函数:
- 不同点:
- 默认匹配的值很可能不一样
instance
没有axios
后面添加的一些方法:create()/CancelToken()/all()
- 看一下
axios
的核心源码,代码如下所示:
'use strict';
var utils = require('./../utils');
var buildURL = require('../helpers/buildURL');
var InterceptorManager = require('./InterceptorManager');
var dispatchRequest = require('./dispatchRequest');
var mergeConfig = require('./mergeConfig');
/**
* Axios构造函数
* Create a new instance of Axios
* @param {Object} instanceConfig The default config for the instance
*/
function Axios(instanceConfig) {
// 将指定的config, 保存为defaults属性
this.defaults = instanceConfig;
// 将包含请求/响应拦截器管理器的对象保存为interceptors属性
this.interceptors = {
request: new InterceptorManager(),
response: new InterceptorManager()
};
}
/**
* 用于发请求的函数
* 我们使用的axios就是此函数bind()返回的函数
*
* Dispatch a request
*
* @param {Object} config The config specific for this request (merged with this.defaults)
*/
Axios.prototype.request = function request(config) {
/*eslint no-param-reassign:0*/
// Allow for axios('example/url'[, config]) a la fetch API
if (typeof config === 'string') {
config = arguments[1] || {
};
config.url = arguments[0];
} else {
config = config || {
};
}
// 合并配置
config = mergeConfig(this.defaults, config);
// 添加method配置, 默认为get
config.method = config.method ? config.method.toLowerCase() : 'get';
/*
创建用于保存请求/响应拦截函数的数组
数组的中间放发送请求的函数
数组的左边放请求拦截器函数(成功/失败)
数组的右边放响应拦截器函数
*/
var chain = [dispatchRequest, undefined];
var promise = Promise.resolve(config);
// 后添加的请求拦截器保存在数组的前面
this.interceptors.request.forEach(function unshiftRequestInterceptors(interceptor) {
chain.unshift(interceptor.fulfilled, interceptor.rejected);
});
// 后添加的响应拦截器保存在数组的后面
this.interceptors.response.forEach(function pushResponseInterceptors(interceptor) {
chain.push(interceptor.fulfilled, interceptor.rejected);
});
// 通过promise的then()串连起所有的请求拦截器/请求方法/响应拦截器
while (chain.length) {
promise = promise.then(chain.shift(), chain.shift());
}
// 返回用来指定我们的onResolved和onRejected的promise
return promise;
};
// 用来得到带query参数的url
Axios.prototype.getUri = function getUri(config) {
config = mergeConfig(this.defaults, config);
return buildURL(config.url, config.params, config.paramsSerializer).replace(/^\?/, '');
};
// Provide aliases for supported request methods
utils.forEach(['delete', 'get', 'head', 'options'], function forEachMethodNoData(method) {
/*eslint func-names:0*/
Axios.prototype[method] = function(url, config) {
return this.request(utils.merge(config || {
}, {
method: method,
url: url
}));
};
});
utils.forEach(['post', 'put', 'patch'], function forEachMethodWithData(method) {
/*eslint func-names:0*/
Axios.prototype[method] = function(url, data, config) {
return this.request(utils.merge(config || {
}, {
method: method,
url: url,
data: data
}));
};
});
module.exports = Axios;
axios
运行的整体流程,如下所示:
- 整体流程:
request(config) ===> dispatchRequest(config) ===> xhrAdapter(config)
request(config)
: 将请求拦截器 /dispatchRequest()
/ 响应拦截器 通过promise
链串连起来, 返回promise
dispatchRequest(config)
: 转换请求数据 ===> 调用xhrAdapter()
发请求 ===> 请求返回后转换响应数据. 返回promise
xhrAdapter(config)
: 创建XHR
对象, 根据config
进行相应设置, 发送特定请求, 并接收响应数据, 返回promise
-
对于
axios
的流程,也可以这么理解:axios
和axios.create()
一起发送请求,被createInstance()
一起接收,配合config
执行/别名执行,Axios.prototype.request
执行,然后执行request.interceptors
,配合处理参数与默认参数/transformdata
执行dispatchRequest
,然后执行adapter
。如果报错或者是cancel
取消,那么执行axios.rejected
。如果正确,那么执行axios fulfilled
。response interceptors
执行,最后请求的onResolved
或者是onRejected
。 -
对于
request
的流程,如下所示:requestInterceptors: [{fulfilled1(){}, rejected1(){}}, {fulfilled2(){}, rejected2(){}}] responseInterceptors: [{fulfilled11(){}, rejected11(){}}, {fulfilled22(){}, rejected22(){}}] chain: [ fulfilled2, rejected2, fulfilled1, rejected1, dispatchReqeust, undefined, fulfilled11, rejected11, fulfilled22, rejected22 ] promise链回调: config => (fulfilled2, rejected2) => (fulfilled1, rejected1) // 请求拦截器处理 => (dispatchReqeust, undefined) // 发请求 => (fulfilled11, rejected11) => (fulfilled22, rejected22) // 响应拦截器处理 => (onResolved, onRejected) // axios发请求回调处理
-
对于
dispatchRequest
的流程,看下源码如下所示:
-
dispatchRequest.js :
'use strict'; var utils = require('./../utils'); var transformData = require('./transformData'); var isCancel = require('../cancel/isCancel'); var defaults = require('../defaults'); var isAbsoluteURL = require('./../helpers/isAbsoluteURL'); var combineURLs = require('./../helpers/combineURLs'); /** * Throws a `Cancel` if cancellation has been requested. */ function throwIfCancellationRequested(config) { if (config.cancelToken) { config.cancelToken.throwIfRequested(); } } /** * Dispatch a request to the server using the configured adapter. * * @param {object} config The config that is to be used for the request * @returns {Promise} The Promise to be fulfilled */ module.exports = function dispatchRequest(config) { /* 如果请求已经被取消, 直接抛出异常 */ throwIfCancellationRequested(config); /* 合并config中的baseURL和url */ if (config.baseURL && !isAbsoluteURL(config.url)) { config.url = combineURLs(config.baseURL, config.url); } // Ensure headers exist config.headers = config.headers || { }; /* 对config中的data进行必要的转换处理 设置相应的Content-Type请求头 */ config.data = transformData( config.data, config.headers, config.transformRequest ); /* 整合config中所有的header */ config.headers = utils.merge( config.headers.common || { }, config.headers[config.method] || { }, config.headers || { } ); utils.forEach( ['delete', 'get', 'head', 'post', 'put', 'patch', 'common'], function cleanHeaderConfig(method) { delete config.headers[method]; } ); var adapter = config.adapter || defaults.adapter; return adapter(config).then(function onAdapterResolution(response) { throwIfCancellationRequested(config); /* 对response中还没有解析的data数据进行解析 json字符串解析为js对象/数组 */ response.data = transformData( response.data, response.headers, config.transformResponse ); return response; }, function onAdapterRejection(reason) { if (!isCancel(reason)) { throwIfCancellationRequested(config); // Transform response data if (reason && reason.response) { reason.response.data = transformData( reason.response.data, reason.response.headers, config.transformResponse ); } } return Promise.reject(reason); }); }; ``` - **InterceptorManager.js** : ```js 'use strict'; var utils = require('./../utils'); function InterceptorManager() { // 用来保存拦截器函数的数组, 数组中每个都是对象, 对象中包含fulfilled/rejected方法 this.handlers = []; } /** * Add a new interceptor to the stack * * @param {Function} fulfilled The function to handle `then` for a `Promise` * @param {Function} rejected The function to handle `reject` for a `Promise` * * @return {Number} An ID used to remove interceptor later */ InterceptorManager.prototype.use = function use(fulfilled, rejected) { // 添加成功和失败的拦截器函数 this.handlers.push({ fulfilled: fulfilled, rejected: rejected }); // 返回拦截器对应的ID(也就是下标) return this.handlers.length - 1; }; /** * Remove an interceptor from the stack * * @param {Number} id The ID that was returned by `use` */ InterceptorManager.prototype.eject = function eject(id) { // 移除指定id对应的拦截器 if (this.handlers[id]) { this.handlers[id] = null; } }; /** * Iterate over all the registered interceptors * * This method is particularly useful for skipping over any * interceptors that may have become `null` calling `eject`. * * @param {Function} fn The function to call for each interceptor */ InterceptorManager.prototype.forEach = function forEach(fn) { // 遍历处理所有保存的拦截器 utils.forEach(this.handlers, function forEachHandler(h) { if (h !== null) { fn(h); } }); }; module.exports = InterceptorManager; ``` - **defaults.js** : ```js 'use strict'; var utils = require('./utils'); var normalizeHeaderName = require('./helpers/normalizeHeaderName'); // 默认的Content-Type头的值 var DEFAULT_CONTENT_TYPE = { 'Content-Type': 'application/x-www-form-urlencoded' }; function setContentTypeIfUnset(headers, value) { if (!utils.isUndefined(headers) && utils.isUndefined(headers['Content-Type'])) { headers['Content-Type'] = value; } } function getDefaultAdapter() { var adapter; // Only Node.JS has a process variable that is of [[Class]] process if (typeof process !== 'undefined' && Object.prototype.toString.call(process) === '[object process]') { // For node use HTTP adapter adapter = require('./adapters/http'); } else if (typeof XMLHttpRequest !== 'undefined') { // For browsers use XHR adapter adapter = require('./adapters/xhr'); } return adapter; } var defaults = { // 得到当前环境对应的请求适配器 adapter: getDefaultAdapter(), // 请求转换器 transformRequest: [function transformRequest(data, headers) { // 指定headers中更规范的请求头属性名 normalizeHeaderName(headers, 'Accept'); normalizeHeaderName(headers, 'Content-Type'); if (utils.isFormData(data) || utils.isArrayBuffer(data) || utils.isBuffer(data) || utils.isStream(data) || utils.isFile(data) || utils.isBlob(data) ) { return data; } if (utils.isArrayBufferView(data)) { return data.buffer; } if (utils.isURLSearchParams(data)) { setContentTypeIfUnset(headers, 'application/x-www-form-urlencoded;charset=utf-8'); return data.toString(); } // 如果data是对象, 指定请求体参数格式为json, 并将参数数据对象转换为json if (utils.isObject(data)) { setContentTypeIfUnset(headers, 'application/json;charset=utf-8'); return JSON.stringify(data); } return data; }], // 响应数据转换器: 解析字符串类型的data数据 transformResponse: [function transformResponse(data) { /*eslint no-param-reassign:0*/ if (typeof data === 'string') { try { data = JSON.parse(data); } catch (e) { /* Ignore */ } } return data; }], /** * A timeout in milliseconds to abort a request. If set to 0 (default) a * timeout is not created. */ timeout: 0, xsrfCookieName: 'XSRF-TOKEN', xsrfHeaderName: 'X-XSRF-TOKEN', maxContentLength: -1, // 判断响应状态码的合法性: [200, 299] validateStatus: function validateStatus(status) { return status >= 200 && status < 300; } }; defaults.headers = { // 包含所有通用的请求的对象 common: { 'Accept': 'application/json, text/plain, */*' } }; // 指定delete/get/head请求方式的请求头容器对象 utils.forEach(['delete', 'get', 'head'], function forEachMethodNoData(method) { defaults.headers[method] = { }; }); // 指定post/put/patch请求方式的请求头容器对象 utils.forEach(['post', 'put', 'patch'], function forEachMethodWithData(method) { // 指定了默认的Content-Type头 defaults.headers[method] = utils.merge(DEFAULT_CONTENT_TYPE); }); module.exports = defaults; ```
axios
的请求/响应拦截器是什么? 如下所示:
- 请求拦截器: 在真正发请求前,可以对请求进行检查或配置进行特定处理的函数, 包括成功/失败的函数, 传递的必须是
config
。失败的回调函数, 传递的默认是error
。 - 响应拦截器: 在请求返回后,可以对响应数据进行特定处理的函数,包括成功/失败的函数,传递的默认是
response
。失败的回调函数, 传递的默认是error
。
axios
的请求/响应数据转换器是什么? 如下所示:
-
请求转换器:对请求头和请求体数据进行特定处理的函数
setContentTypeIfUnset(headers, 'application/json;charset=utf-8'); return JSON.stringify(data)
,如下:if (utils.isObject(data)) { setContentTypeIfUnset(headers, 'application/json;charset=utf-8'); return JSON.stringify(data); }
-
响应转换器: 将响应体
json
字符串解析为js
对象或数组的函数
response.data = JSON.parse(response.data)
- 对于
xhrAdapter
的流程,看下 xhr.js 的源码,如下所示:
'use strict';
var utils = require('./../utils');
var settle = require('./../core/settle');
var buildURL = require('./../helpers/buildURL');
var parseHeaders = require('./../helpers/parseHeaders');
var isURLSameOrigin = require('./../helpers/isURLSameOrigin');
var createError = require('../core/createError');
module.exports = function xhrAdapter(config) {
// 返回一个promise
return new Promise(function dispatchXhrRequest(resolve, reject) {
var requestData = config.data;
var requestHeaders = config.headers;
if (utils.isFormData(requestData)) {
delete requestHeaders['Content-Type']; // Let the browser set it
}
// 创建XHR对象
var request = new XMLHttpRequest();
// HTTP basic authentication
if (config.auth) {
var username = config.auth.username || '';
var password = config.auth.password || '';
requestHeaders.Authorization = 'Basic ' + btoa(username + ':' + password);
}
// 初始化请求
request.open(config.method.toUpperCase(), buildURL(config.url, config.params, config.paramsSerializer), true);
// 指定超时时间(单位ms)
request.timeout = config.timeout;
// 绑定请求状态改变的监听
request.onreadystatechange = function handleLoad() {
// request不存在或请求状态不是4, 直接结束
if (!request || request.readyState !== 4) {
return;
}
// The request errored out and we didn't get a response, this will be
// handled by onerror instead
// With one exception: request that using file: protocol, most browsers
// will return status as 0 even though it's a successful request
if (request.status === 0 && !(request.responseURL && request.responseURL.indexOf('file:') === 0)) {
return;
}
// 准备response对象
var responseHeaders = 'getAllResponseHeaders' in request ? parseHeaders(request.getAllResponseHeaders()) : null;
var responseData = !config.responseType || config.responseType === 'text' ? request.responseText : request.response;
var response = {
data: responseData,
status: request.status,
statusText: request.statusText,
headers: responseHeaders,
config: config,
request: request
};
// 根据响应状态码来确定请求的promise的结果状态(成功/失败)
settle(resolve, reject, response);
// 将请求对象赋空
request = null;
};
// 绑定请求中断监听
request.onabort = function handleAbort() {
if (!request) {
return;
}
// reject promise, 指定aborted的error
reject(createError('Request aborted', config, 'ECONNABORTED', request));
// Clean up request
request = null;
};
// Handle low level network errors
request.onerror = function handleError() {
// Real errors are hidden from us by the browser
// onerror should only fire if it's a network error
reject(createError('Network Error', config, null, request));
// Clean up request
request = null;
};
// Handle timeout
request.ontimeout = function handleTimeout() {
reject(createError('timeout of ' + config.timeout + 'ms exceeded', config, 'ECONNABORTED',
request));
// Clean up request
request = null;
};
// Add xsrf header
// This is only done if running in a standard browser environment.
// Specifically not if we're in a web worker, or react-native.
if (utils.isStandardBrowserEnv()) {
var cookies = require('./../helpers/cookies');
// Add xsrf header
var xsrfValue = (config.withCredentials || isURLSameOrigin(config.url)) && config.xsrfCookieName ?
cookies.read(config.xsrfCookieName) :
undefined;
if (xsrfValue) {
requestHeaders[config.xsrfHeaderName] = xsrfValue;
}
}
// 如果没有指定请求体参数, 删除Content-Type请求头, 其它所有请求头都设置到request上
// Add headers to the request
if ('setRequestHeader' in request) {
utils.forEach(requestHeaders, function setRequestHeader(val, key) {
if (typeof requestData === 'undefined' && key.toLowerCase() === 'content-type') {
// Remove Content-Type if data is undefined
delete requestHeaders[key];
} else {
// Otherwise add header to the request
request.setRequestHeader(key, val);
}
});
}
// Add withCredentials to request if needed
if (config.withCredentials) {
request.withCredentials = true;
}
// 如果需要指定responseType
// Add responseType to request if needed
if (config.responseType) {
try {
request.responseType = config.responseType;
} catch (e) {
// Expected DOMException thrown by browsers not compatible XMLHttpRequest Level 2.
// But, this can be suppressed for 'json' type as it can be parsed by default 'transformResponse' function.
if (config.responseType !== 'json') {
throw e;
}
}
}
// 绑定下载进度的监听
// Handle progress if needed
if (typeof config.onDownloadProgress === 'function') {
request.addEventListener('progress', config.onDownloadProgress);
}
// 绑定上传进度的监听
// Not all browsers support upload events
if (typeof config.onUploadProgress === 'function' && request.upload) {
request.upload.addEventListener('progress', config.onUploadProgress);
}
// 如果配置了cancelToken
if (config.cancelToken) {
// 指定用于中断请求的回调函数
config.cancelToken.promise.then(function onCanceled(cancel) {
if (!request) {
return;
}
// 中断请求
request.abort();
// 让请求的promise失败
reject(cancel);
// Clean up request
request = null;
});
}
if (requestData === undefined) {
requestData = null;
}
// 发送请求, 指定请求体数据, 可能是null
request.send(requestData);
});
};
-
response
的整体结构,如下所示:{ data, status, statusText, headers, config, request }
-
error
的整体结构,如下所示:{ message, request, response }
-
对于
cancel
取消的流程,看下源码如下所示:扫描二维码关注公众号,回复: 12826798 查看本文章- Cancel.js :
'use strict'; /** * 当取消一个请求时, 需要将Cancel对象作为一个error抛出 * * A `Cancel` is an object that is thrown when an operation is canceled. * * @class * @param {string=} message The message. */ function Cancel(message) { this.message = message; } Cancel.prototype.toString = function toString() { return 'Cancel' + (this.message ? ': ' + this.message : ''); }; // 用于标识是一个取消的error Cancel.prototype.__CANCEL__ = true; module.exports = Cancel;
- isCancel.js :
'use strict'; /* 用于判断一个error是不是一个cancel错误 */ module.exports = function isCancel(value) { return !!(value && value.__CANCEL__); };
- CancelToken.js :
'use strict'; var Cancel = require('./Cancel'); /** * 用于取消请求的对象构造函数 * * A `CancelToken` is an object that can be used to request cancellation of an operation. * * @class * @param {Function} executor The executor function. */ function CancelToken(executor) { if (typeof executor !== 'function') { throw new TypeError('executor must be a function.'); } // 为取消请求准备一个promise对象, 并保存resolve函数 var resolvePromise; this.promise = new Promise(function promiseExecutor(resolve) { resolvePromise = resolve; }); // 保存当前token对象 var token = this; // 立即执行接收的执行器函数, 并传入用于取消请求的cancel函数 executor(function cancel(message) { // 如果token中有reason了, 说明请求已取消 if (token.reason) { // Cancellation has already been requested return; } // 将token的reason指定为一个Cancel对象 token.reason = new Cancel(message); // 将取消请求的promise指定为成功, 值为reason resolvePromise(token.reason); }); } /** * 如果请求已经被取消, 抛出reason也就是Cancel对象的异常 * Throws a `Cancel` if cancellation has been requested. */ CancelToken.prototype.throwIfRequested = function throwIfRequested() { if (this.reason) { throw this.reason; } }; /** * 创建一个包含token对象和cancel函数的对象, 并添加给CancelToken * * Returns an object that contains a new `CancelToken` and a function that, when called, * cancels the `CancelToken`. */ CancelToken.source = function source() { var cancel; var token = new CancelToken(function executor(c) { cancel = c; }); return { token: token, cancel: cancel }; }; module.exports = CancelToken;
- Cancel.js :
-
如何取消未完成的请求,如下所示:
- 当配置了
cancelToken
对象时,保存cancel
函数,如下:- 创建一个用于将来中断请求的
cancelPromise
- 并定义了一个用于取消请求的
cancel
函数 - 将
cancel
函数传递出来
- 创建一个用于将来中断请求的
- 调用
cancel()
取消请求,如下:- 执行
cacel
函数, 传入错误信息message
- 内部会让
cancelPromise
变为成功, 且成功的值为一个Cancel
对象 - 在
cancelPromise
的成功回调中中断请求, 并让发请求的proimse
失败, 失败的reason
为Cacel
对象
- 执行